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2017-03-02sched/headers: Prepare for new header dependencies before moving code to ↵Ingo Molnar1-0/+1
<linux/sched/debug.h> We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder <linux/sched/debug.h> file that just maps to <linux/sched.h> to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-03-02sched/headers: Prepare for new header dependencies before moving code to ↵Ingo Molnar1-0/+1
<linux/sched/clock.h> We are going to split <linux/sched/clock.h> out of <linux/sched.h>, which will have to be picked up from other headers and .c files. Create a trivial placeholder <linux/sched/clock.h> file that just maps to <linux/sched.h> to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-02-22Merge branch 'for-linus' of ↵Linus Torvalds4-237/+310
git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk Pull printk updates from Petr Mladek: - Add Petr Mladek, Sergey Senozhatsky as printk maintainers, and Steven Rostedt as the printk reviewer. This idea came up after the discussion about printk issues at Kernel Summit. It was formulated and discussed at lkml[1]. - Extend a lock-less NMI per-cpu buffers idea to handle recursive printk() calls by Sergey Senozhatsky[2]. It is the first step in sanitizing printk as discussed at Kernel Summit. The change allows to see messages that would normally get ignored or would cause a deadlock. Also it allows to enable lockdep in printk(). This already paid off. The testing in linux-next helped to discover two old problems that were hidden before[3][4]. - Remove unused parameter by Sergey Senozhatsky. Clean up after a past change. [1] http://lkml.kernel.org/r/1481798878-31898-1-git-send-email-pmladek@suse.com [2] http://lkml.kernel.org/r/20161227141611.940-1-sergey.senozhatsky@gmail.com [3] http://lkml.kernel.org/r/20170215044332.30449-1-sergey.senozhatsky@gmail.com [4] http://lkml.kernel.org/r/20170217015932.11898-1-sergey.senozhatsky@gmail.com * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: printk: drop call_console_drivers() unused param printk: convert the rest to printk-safe printk: remove zap_locks() function printk: use printk_safe buffers in printk printk: report lost messages in printk safe/nmi contexts printk: always use deferred printk when flush printk_safe lines printk: introduce per-cpu safe_print seq buffer printk: rename nmi.c and exported api printk: use vprintk_func in vprintk() MAINTAINERS: Add printk maintainers
2017-02-18printk: use rcuidle console tracepointSergey Senozhatsky1-1/+1
Use rcuidle console tracepoint because, apparently, it may be issued from an idle CPU: hw-breakpoint: Failed to enable monitor mode on CPU 0. hw-breakpoint: CPU 0 failed to disable vector catch =============================== [ ERR: suspicious RCU usage. ] 4.10.0-rc8-next-20170215+ #119 Not tainted ------------------------------- ./include/trace/events/printk.h:32 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from idle CPU! rcu_scheduler_active = 2, debug_locks = 0 RCU used illegally from extended quiescent state! 2 locks held by swapper/0/0: #0: (cpu_pm_notifier_lock){......}, at: [<c0237e2c>] cpu_pm_exit+0x10/0x54 #1: (console_lock){+.+.+.}, at: [<c01ab350>] vprintk_emit+0x264/0x474 stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.10.0-rc8-next-20170215+ #119 Hardware name: Generic OMAP4 (Flattened Device Tree) console_unlock vprintk_emit vprintk_default printk reset_ctrl_regs dbg_cpu_pm_notify notifier_call_chain cpu_pm_exit omap_enter_idle_coupled cpuidle_enter_state cpuidle_enter_state_coupled do_idle cpu_startup_entry start_kernel This RCU warning, however, is suppressed by lockdep_off() in printk(). lockdep_off() increments the ->lockdep_recursion counter and thus disables RCU_LOCKDEP_WARN() and debug_lockdep_rcu_enabled(), which want lockdep to be enabled "current->lockdep_recursion == 0". Link: http://lkml.kernel.org/r/20170217015932.11898-1-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reported-by: Tony Lindgren <tony@atomide.com> Tested-by: Tony Lindgren <tony@atomide.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Lindgren <tony@atomide.com> Cc: Russell King <rmk@armlinux.org.uk> Cc: <stable@vger.kernel.org> [3.4+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-08printk: drop call_console_drivers() unused paramSergey Senozhatsky1-8/+4
We do suppress_message_printing() check before we call call_console_drivers() now, so `level' param is not needed anymore. Link: http://lkml.kernel.org/r/20161224140902.1962-2-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
2017-02-08printk: convert the rest to printk-safeSergey Senozhatsky1-38/+65
This patch converts the rest of logbuf users (which are out of printk recursion case, but can deadlock in printk). To make printk-safe usage easier the patch introduces 4 helper macros: - logbuf_lock_irq()/logbuf_unlock_irq() lock/unlock the logbuf lock and disable/enable local IRQ - logbuf_lock_irqsave(flags)/logbuf_unlock_irqrestore(flags) lock/unlock the logbuf lock and saves/restores local IRQ state Link: http://lkml.kernel.org/r/20161227141611.940-9-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
2017-02-08printk: remove zap_locks() functionSergey Senozhatsky1-61/+0
We use printk-safe now which makes printk-recursion detection code in vprintk_emit() unreachable. The tricky thing here is that, apart from detecting and reporting printk recursions, that code also used to zap_locks() in case of panic() from the same CPU. However, zap_locks() does not look to be needed anymore: 1) Since commit 08d78658f393 ("panic: release stale console lock to always get the logbuf printed out") panic flushing of `logbuf' to console ignores the state of `console_sem' by doing panic() console_trylock(); console_unlock(); 2) Since commit cf9b1106c81c ("printk/nmi: flush NMI messages on the system panic") panic attempts to zap the `logbuf_lock' spin_lock to successfully flush nmi messages to `logbuf'. Basically, it seems that we either already do what zap_locks() used to do but in other places or we ignore the state of the lock. The only reaming difference is that we don't re-init the console semaphore in printk_safe_flush_on_panic(), but this is not necessary because we don't call console drivers from printk_safe_flush_on_panic() due to the fact that we are using a deferred printk() version (as was suggested by Petr Mladek). Link: http://lkml.kernel.org/r/20161227141611.940-8-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
2017-02-08printk: use printk_safe buffers in printkSergey Senozhatsky1-15/+32
Use printk_safe per-CPU buffers in printk recursion-prone blocks: -- around logbuf_lock protected sections in vprintk_emit() and console_unlock() -- around down_trylock_console_sem() and up_console_sem() Note that this solution addresses deadlocks caused by printk() recursive calls only. That is vprintk_emit() and console_unlock(). The rest will be converted in a followup patch. Another thing to note is that we now keep lockdep enabled in printk, because we are protected against the printk recursion caused by lockdep in vprintk_emit() by the printk-safe mechanism - we first switch to per-CPU buffers and only then access the deadlock-prone locks. Examples: 1) printk() from logbuf_lock spin_lock section Assume the following code: printk() raw_spin_lock(&logbuf_lock); WARN_ON(1); raw_spin_unlock(&logbuf_lock); which now produces: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 366 at kernel/printk/printk.c:1811 vprintk_emit CPU: 0 PID: 366 Comm: bash Call Trace: warn_slowpath_null+0x1d/0x1f vprintk_emit+0x1cd/0x438 vprintk_default+0x1d/0x1f printk+0x48/0x50 [..] 2) printk() from semaphore sem->lock spin_lock section Assume the following code printk() console_trylock() down_trylock() raw_spin_lock_irqsave(&sem->lock, flags); WARN_ON(1); raw_spin_unlock_irqrestore(&sem->lock, flags); which now produces: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 363 at kernel/locking/semaphore.c:141 down_trylock CPU: 1 PID: 363 Comm: bash Call Trace: warn_slowpath_null+0x1d/0x1f down_trylock+0x3d/0x62 ? vprintk_emit+0x3f9/0x414 console_trylock+0x31/0xeb vprintk_emit+0x3f9/0x414 vprintk_default+0x1d/0x1f printk+0x48/0x50 [..] 3) printk() from console_unlock() Assume the following code: printk() console_unlock() raw_spin_lock(&logbuf_lock); WARN_ON(1); raw_spin_unlock(&logbuf_lock); which now produces: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 329 at kernel/printk/printk.c:2384 console_unlock CPU: 1 PID: 329 Comm: bash Call Trace: warn_slowpath_null+0x18/0x1a console_unlock+0x12d/0x559 ? trace_hardirqs_on_caller+0x16d/0x189 ? trace_hardirqs_on+0xd/0xf vprintk_emit+0x363/0x374 vprintk_default+0x18/0x1a printk+0x43/0x4b [..] 4) printk() from try_to_wake_up() Assume the following code: printk() console_unlock() up() try_to_wake_up() raw_spin_lock_irqsave(&p->pi_lock, flags); WARN_ON(1); raw_spin_unlock_irqrestore(&p->pi_lock, flags); which now produces: ------------[ cut here ]------------ WARNING: CPU: 3 PID: 363 at kernel/sched/core.c:2028 try_to_wake_up CPU: 3 PID: 363 Comm: bash Call Trace: warn_slowpath_null+0x1d/0x1f try_to_wake_up+0x7f/0x4f7 wake_up_process+0x15/0x17 __up.isra.0+0x56/0x63 up+0x32/0x42 __up_console_sem+0x37/0x55 console_unlock+0x21e/0x4c2 vprintk_emit+0x41c/0x462 vprintk_default+0x1d/0x1f printk+0x48/0x50 [..] 5) printk() from call_console_drivers() Assume the following code: printk() console_unlock() call_console_drivers() ... WARN_ON(1); which now produces: ------------[ cut here ]------------ WARNING: CPU: 2 PID: 305 at kernel/printk/printk.c:1604 call_console_drivers CPU: 2 PID: 305 Comm: bash Call Trace: warn_slowpath_null+0x18/0x1a call_console_drivers.isra.6.constprop.16+0x3a/0xb0 console_unlock+0x471/0x48e vprintk_emit+0x1f4/0x206 vprintk_default+0x18/0x1a vprintk_func+0x6e/0x70 printk+0x3e/0x46 [..] 6) unsupported placeholder in printk() format now prints an actual warning from vscnprintf(), instead of 'BUG: recent printk recursion!'. ------------[ cut here ]------------ WARNING: CPU: 5 PID: 337 at lib/vsprintf.c:1900 format_decode Please remove unsupported % in format string CPU: 5 PID: 337 Comm: bash Call Trace: dump_stack+0x4f/0x65 __warn+0xc2/0xdd warn_slowpath_fmt+0x4b/0x53 format_decode+0x22c/0x308 vsnprintf+0x89/0x3b7 vscnprintf+0xd/0x26 vprintk_emit+0xb4/0x238 vprintk_default+0x1d/0x1f vprintk_func+0x6c/0x73 printk+0x43/0x4b [..] Link: http://lkml.kernel.org/r/20161227141611.940-7-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2017-02-08printk: report lost messages in printk safe/nmi contextsSergey Senozhatsky3-37/+28
Account lost messages in pritk-safe and printk-safe-nmi contexts and report those numbers during printk_safe_flush(). The patch also moves lost message counter to struct `printk_safe_seq_buf' instead of having dedicated static counters - this simplifies the code. Link: http://lkml.kernel.org/r/20161227141611.940-6-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
2017-02-08printk: always use deferred printk when flush printk_safe linesSergey Senozhatsky1-8/+6
Always use printk_deferred() in printk_safe_flush_line(). Flushing can be done from NMI or printk_safe contexts (when we are in panic), so we can't call console drivers, yet still want to store the messages in the logbuf buffer. Therefore we use a deferred printk version. Link: http://lkml.kernel.org/r/20170206164253.GA463@tigerII.localdomain Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Suggested-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2017-02-08printk: introduce per-cpu safe_print seq bufferSergey Senozhatsky4-52/+157
This patch extends the idea of NMI per-cpu buffers to regions that may cause recursive printk() calls and possible deadlocks. Namely, printk() can't handle printk calls from schedule code or printk() calls from lock debugging code (spin_dump() for instance); because those may be called with `sem->lock' already taken or any other `critical' locks (p->pi_lock, etc.). An example of deadlock can be vprintk_emit() console_unlock() up() << raw_spin_lock_irqsave(&sem->lock, flags); wake_up_process() try_to_wake_up() ttwu_queue() ttwu_activate() activate_task() enqueue_task() enqueue_task_fair() cfs_rq_of() task_of() WARN_ON_ONCE(!entity_is_task(se)) vprintk_emit() console_trylock() down_trylock() raw_spin_lock_irqsave(&sem->lock, flags) ^^^^ deadlock and some other cases. Just like in NMI implementation, the solution uses a per-cpu `printk_func' pointer to 'redirect' printk() calls to a 'safe' callback, that store messages in a per-cpu buffer and flushes them back to logbuf buffer later. Usage example: printk() printk_safe_enter_irqsave(flags) // // any printk() call from here will endup in vprintk_safe(), // that stores messages in a special per-CPU buffer. // printk_safe_exit_irqrestore(flags) The 'redirection' mechanism, though, has been reworked, as suggested by Petr Mladek. Instead of using a per-cpu @print_func callback we now keep a per-cpu printk-context variable and call either default or nmi vprintk function depending on its value. printk_nmi_entrer/exit and printk_safe_enter/exit, thus, just set/celar corresponding bits in printk-context functions. The patch only adds printk_safe support, we don't use it yet. Link: http://lkml.kernel.org/r/20161227141611.940-4-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2017-02-08printk: rename nmi.c and exported apiSergey Senozhatsky2-33/+33
A preparation patch for printk_safe work. No functional change. - rename nmi.c to print_safe.c - add `printk_safe' prefix to some (which used both by printk-safe and printk-nmi) of the exported functions. Link: http://lkml.kernel.org/r/20161227141611.940-3-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
2017-02-08printk: use vprintk_func in vprintk()Sergey Senozhatsky1-1/+1
vprintk(), just like printk(), better be using per-cpu printk_func instead of direct vprintk_emit() call. Just in case if vprintk() will ever be called from NMI, or from any other context that can deadlock in printk(). Link: http://lkml.kernel.org/r/20161227141611.940-2-sergey.senozhatsky@gmail.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jan Kara <jack@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Calvin Owens <calvinowens@fb.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Petr Mladek <pmladek@suse.com>
2016-12-24Replace <asm/uaccess.h> with <linux/uaccess.h> globallyLinus Torvalds1-1/+1
This was entirely automated, using the script by Al: PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*<asm/uaccess.h>' sed -i -e "s!$PATT!#include <linux/uaccess.h>!" \ $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h) to do the replacement at the end of the merge window. Requested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-16Merge branch 'for-linus' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs updates from Al Viro: - more ->d_init() stuff (work.dcache) - pathname resolution cleanups (work.namei) - a few missing iov_iter primitives - copy_from_iter_full() and friends. Either copy the full requested amount, advance the iterator and return true, or fail, return false and do _not_ advance the iterator. Quite a few open-coded callers converted (and became more readable and harder to fuck up that way) (work.iov_iter) - several assorted patches, the big one being logfs removal * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: logfs: remove from tree vfs: fix put_compat_statfs64() does not handle errors namei: fold should_follow_link() with the step into not-followed link namei: pass both WALK_GET and WALK_MORE to should_follow_link() namei: invert WALK_PUT logics namei: shift interpretation of LOOKUP_FOLLOW inside should_follow_link() namei: saner calling conventions for mountpoint_last() namei.c: get rid of user_path_parent() switch getfrag callbacks to ..._full() primitives make skb_add_data,{_nocache}() and skb_copy_to_page_nocache() advance only on success [iov_iter] new primitives - copy_from_iter_full() and friends don't open-code file_inode() ceph: switch to use of ->d_init() ceph: unify dentry_operations instances lustre: switch to use of ->d_init()
2016-12-15printk: Remove no longer used second struct contGeert Uytterhoeven1-6/+0
If CONFIG_PRINTK=n: kernel/printk/printk.c:1893: warning: ‘cont’ defined but not used Note that there are actually two different struct cont definitions and objects: the first one is used if CONFIG_PRINTK=y, the second one became unused by removing console_cont_flush(). Fixes: 5c2992ee7fd8 ("printk: remove console flushing special cases for partial buffered lines") Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Petr Mladek <pmladek@suse.com> [ I do the occasional "allnoconfig" builds, but apparently not often enough - Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-14printk: remove console flushing special cases for partial buffered linesLinus Torvalds1-103/+5
It actively hurts proper merging, and makes for a lot of special cases. There was a good(ish) reason for doing it originally, but it's getting too painful to maintain. And most of the original reasons for it are long gone. So instead of having special code to flush partial lines to the console (as opposed to the record buffers), do _all_ the console writing from the record buffer, and be done with it. If an oops happens (or some other synchronous event), we will flush the partial lines due to the oops printing activity, so this does not affect that. It does mean that if you have a completely hung machine, a partial preceding line may not have been printed out. That was some of the original reason for this complexity, in fact, back when we used to test for the historical i386 "halt" instruction problem by doing pr_info("Checking 'hlt' instruction... "); if (!boot_cpu_data.hlt_works_ok) { pr_cont("disabled\n"); return; } halt(); halt(); halt(); halt(); pr_cont("OK\n"); and that model no longer works (it the 'hlt' instruction kills the machine, the partial line won't have been flushed, so you won't even see it). Of course, that was also back in the days when people actually had textual console output rather than a graphical splash-screen at bootup. How times change.. Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: Joe Perches <joe@perches.com> Cc: Steven Rostedt <rostedt@goodmis.org> Tested-by: Petr Mladek <pmladek@suse.com> Tested-by: Geert Uytterhoeven <geert@linux-m68k.org> Tested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-14printk: remove games with previous record flagsLinus Torvalds1-85/+24
The record logging code looks at the previous record flags in various ways, and they are all wrong. You can't use the previous record flags to determine anything about the next record, because they may simply not be related. In particular, the reason the previous record was a continuation record may well be exactly _because_ the new record was printed by a different process, which is why the previous record was flushed. So all those games are simply wrong, and make the code hard to understand (because the code fundamentally cdoes not make sense). So remove it. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-14kdb: call vkdb_printf() from vprintk_default() only when wantedPetr Mladek1-1/+2
kdb_trap_printk allows to pass normal printk() messages to kdb via vkdb_printk(). For example, it is used to get backtrace using the classic show_stack(), see kdb_show_stack(). vkdb_printf() tries to avoid a potential infinite loop by disabling the trap. But this approach is racy, for example: CPU1 CPU2 vkdb_printf() // assume that kdb_trap_printk == 0 saved_trap_printk = kdb_trap_printk; kdb_trap_printk = 0; kdb_show_stack() kdb_trap_printk++; Problem1: Now, a nested printk() on CPU0 calls vkdb_printf() even when it should have been disabled. It will not cause a deadlock but... // using the outdated saved value: 0 kdb_trap_printk = saved_trap_printk; kdb_trap_printk--; Problem2: Now, kdb_trap_printk == -1 and will stay like this. It means that all messages will get passed to kdb from now on. This patch removes the racy saved_trap_printk handling. Instead, the recursion is prevented by a check for the locked CPU. The solution is still kind of racy. A non-related printk(), from another process, might get trapped by vkdb_printf(). And the wanted printk() might not get trapped because kdb_printf_cpu is assigned. But this problem existed even with the original code. A proper solution would be to get_cpu() before setting kdb_trap_printk and trap messages only from this CPU. I am not sure if it is worth the effort, though. In fact, the race is very theoretical. When kdb is running any of the commands that use kdb_trap_printk there is a single active CPU and the other CPUs should be in a holding pen inside kgdb_cpu_enter(). The only time this is violated is when there is a timeout waiting for the other CPUs to report to the holding pen. Finally, note that the situation is a bit schizophrenic. vkdb_printf() explicitly allows recursion but only from KDB code that calls kdb_printf() directly. On the other hand, the generic printk() recursion is not allowed because it might cause an infinite loop. This is why we could not hide the decision inside vkdb_printf() easily. Link: http://lkml.kernel.org/r/1480412276-16690-4-git-send-email-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-12Merge branch 'akpm' (patches from Andrew)Linus Torvalds1-30/+53
Merge updates from Andrew Morton: - various misc bits - most of MM (quite a lot of MM material is awaiting the merge of linux-next dependencies) - kasan - printk updates - procfs updates - MAINTAINERS - /lib updates - checkpatch updates * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (123 commits) init: reduce rootwait polling interval time to 5ms binfmt_elf: use vmalloc() for allocation of vma_filesz checkpatch: don't emit unified-diff error for rename-only patches checkpatch: don't check c99 types like uint8_t under tools checkpatch: avoid multiple line dereferences checkpatch: don't check .pl files, improve absolute path commit log test scripts/checkpatch.pl: fix spelling checkpatch: don't try to get maintained status when --no-tree is given lib/ida: document locking requirements a bit better lib/rbtree.c: fix typo in comment of ____rb_erase_color lib/Kconfig.debug: make CONFIG_STRICT_DEVMEM depend on CONFIG_DEVMEM MAINTAINERS: add drm and drm/i915 irc channels MAINTAINERS: add "C:" for URI for chat where developers hang out MAINTAINERS: add drm and drm/i915 bug filing info MAINTAINERS: add "B:" for URI where to file bugs get_maintainer: look for arbitrary letter prefixes in sections printk: add Kconfig option to set default console loglevel printk/sound: handle more message headers printk/btrfs: handle more message headers printk/kdb: handle more message headers ...
2016-12-12Merge branch 'smp-hotplug-for-linus' of ↵Linus Torvalds1-13/+12
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull smp hotplug updates from Thomas Gleixner: "This is the final round of converting the notifier mess to the state machine. The removal of the notifiers and the related infrastructure will happen around rc1, as there are conversions outstanding in other trees. The whole exercise removed about 2000 lines of code in total and in course of the conversion several dozen bugs got fixed. The new mechanism allows to test almost every hotplug step standalone, so usage sites can exercise all transitions extensively. There is more room for improvement, like integrating all the pointlessly different architecture mechanisms of synchronizing, setting cpus online etc into the core code" * 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits) tracing/rb: Init the CPU mask on allocation soc/fsl/qbman: Convert to hotplug state machine soc/fsl/qbman: Convert to hotplug state machine zram: Convert to hotplug state machine KVM/PPC/Book3S HV: Convert to hotplug state machine arm64/cpuinfo: Convert to hotplug state machine arm64/cpuinfo: Make hotplug notifier symmetric mm/compaction: Convert to hotplug state machine iommu/vt-d: Convert to hotplug state machine mm/zswap: Convert pool to hotplug state machine mm/zswap: Convert dst-mem to hotplug state machine mm/zsmalloc: Convert to hotplug state machine mm/vmstat: Convert to hotplug state machine mm/vmstat: Avoid on each online CPU loops mm/vmstat: Drop get_online_cpus() from init_cpu_node_state/vmstat_cpu_dead() tracing/rb: Convert to hotplug state machine oprofile/nmi timer: Convert to hotplug state machine net/iucv: Use explicit clean up labels in iucv_init() x86/pci/amd-bus: Convert to hotplug state machine x86/oprofile/nmi: Convert to hotplug state machine ...
2016-12-12printk/NMI: handle continuous lines and missing newlinePetr Mladek1-28/+50
Commit 4bcc595ccd80 ("printk: reinstate KERN_CONT for printing continuation lines") added back KERN_CONT message header. As a result it might appear in the middle of the line when the parts are squashed via the temporary NMI buffer. A reasonable solution seems to be to split the text in the NNI temporary not only by newlines but also by the message headers. Another solution would be to filter out KERN_CONT when writing to the temporary buffer. But this would complicate the lockless handling. Also it would not solve problems with a missing newline that was there even before the KERN_CONT stuff. This patch moves the temporary buffer handling into separate function. I played with it and it seems that using the char pointers make the code easier to read. Also it prints the final newline as a continuous line. Finally, it moves handling of the s->len overflow into the paranoid check. And allows to recover from the disaster. Link: http://lkml.kernel.org/r/1478695291-12169-2-git-send-email-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Joe Perches <joe@perches.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Jaroslav Kysela <perex@perex.cz> Cc: Takashi Iwai <tiwai@suse.com> Cc: Chris Mason <clm@fb.com> Cc: Josef Bacik <jbacik@fb.com> Cc: David Sterba <dsterba@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-12printk/NMI: fix up handling of the full nmi log bufferPetr Mladek1-2/+3
vsnprintf() adds the trailing '\0' but it does not count it into the number of printed characters. The result is that there is one byte less space for the real characters in the buffer. The broken check for the free space might cause that we will repeatedly try to print 1 character into the buffer, never reach the full buffer, and do not count the messages as missed. Also vsnprintf() returns the number of characters that would be printed if the buffer was big enough. As a result, s->len might be bigger than the size of the buffer[*]. And the printk() function might return bigger len than it really printed. Both problems are fixed by using vscnprintf() instead. Note that I though about increasing the number of missed messages even when the message was shrunken. But it made the code even more complicated. I think that it is not worth it. Shrunken messages are usually easy to recognize. And it should be a corner case. [*] The overflown s->len value is crazy and unexpected. I "made a mistake" and reported this situation as an internal error when fixed handling of PR_CONT headers in some other patch. Link: http://lkml.kernel.org/r/20161208174912.GA17042@linux.suse Signed-off-by: Petr Mladek <pmladek@suse.com> CcL Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: Chris Mason <clm@fb.com> Cc: David Sterba <dsterba@suse.com> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Josef Bacik <jbacik@fb.com> Cc: Joe Perches <joe@perches.com> Cc: Jaroslav Kysela <perex@perex.cz> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Takashi Iwai <tiwai@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-05[iov_iter] new primitives - copy_from_iter_full() and friendsAl Viro1-1/+1
copy_from_iter_full(), copy_from_iter_full_nocache() and csum_and_copy_from_iter_full() - counterparts of copy_from_iter() et.al., advancing iterator only in case of successful full copy and returning whether it had been successful or not. Convert some obvious users. *NOTE* - do not blindly assume that something is a good candidate for those unless you are sure that not advancing iov_iter in failure case is the right thing in this case. Anything that does short read/short write kind of stuff (or is in a loop, etc.) is unlikely to be a good one. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-11-17kernel/printk: Block cpuhotplug callback when tasks are frozenThomas Gleixner1-2/+4
The recent conversion of the console hotplug notifier to the state machine missed the fact, that the notifier only operated on the non frozen transitions. As a consequence the console_lock/unlock() pair is also invoked during suspend, which results in a lockdep warning. Restore the previous state by making the lock/unlock conditional on !tasks_frozen. Fixes: 90b14889d2f9 ("kernel/printk: Convert to hotplug state machine") Reported-and-tested-by: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1611171729320.3645@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2016-11-14Revert "printk: make reading the kernel log flush pending lines"Linus Torvalds1-11/+0
This reverts commit bfd8d3f23b51018388be0411ccbc2d56277fe294. It turns out that this flushes things much too aggressiverly, and causes lines to break up when the system logger races with new continuation lines being printed. There's a pending patch to make printk() flushing much more straightforward, but it's too invasive for 4.9, so in the meantime let's just not make the system message logging flush continuation lines. They'll be flushed by the final newline anyway. Suggested-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-11-11Revert "console: don't prefer first registered if DT specifies stdout-path"Hans de Goede1-12/+1
This reverts commit 05fd007e4629 ("console: don't prefer first registered if DT specifies stdout-path"). The reverted commit changes existing behavior on which many ARM boards rely. Many ARM small-board-computers, like e.g. the Raspberry Pi have both a video output and a serial console. Depending on whether the user is using the device as a more regular computer; or as a headless device we need to have the console on either one or the other. Many users rely on the kernel behavior of the console being present on both outputs, before the reverted commit the console setup with no console= kernel arguments on an ARM board which sets stdout-path in dt would look like this: [root@localhost ~]# cat /proc/consoles ttyS0 -W- (EC p a) 4:64 tty0 -WU (E p ) 4:1 Where as after the reverted commit, it looks like this: [root@localhost ~]# cat /proc/consoles ttyS0 -W- (EC p a) 4:64 This commit reverts commit 05fd007e4629 ("console: don't prefer first registered if DT specifies stdout-path") restoring the original behavior. Fixes: 05fd007e4629 ("console: don't prefer first registered if DT specifies stdout-path") Link: http://lkml.kernel.org/r/20161104121135.4780-2-hdegoede@redhat.com Signed-off-by: Hans de Goede <hdegoede@redhat.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: Frank Rowand <frowand.list@gmail.com> Cc: Thorsten Leemhuis <regressions@leemhuis.info> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-11-09kernel/printk: Convert to hotplug state machineSebastian Andrzej Siewior1-16/+13
Install the callbacks via the state machine. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/20161103145021.28528-3-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-10-19printk: suppress empty continuation linesLinus Torvalds1-0/+4
We have a fairly common pattern where you print several things as continuations on one single line in a loop, and then at the end you do printk(KERN_CONT "\n"); to flush the buffered output. But if the output was flushed by something else (concurrent printk activity, or just system logging), we don't want that final flushing to just print an empty line. So just suppress empty continuation lines when they couldn't be merged into the line they are a continuation of. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-10Merge branch 'printk-cleanups'Linus Torvalds1-63/+61
Merge my system logging cleanups, triggered by the broken '\n' patches. The line continuation handling has been broken basically forever, and the code to handle the system log records was both confusing and dubious. And it would do entirely the wrong thing unless you always had a terminating newline, partly because it couldn't actually see whether a message was marked KERN_CONT or not (but partly because the LOG_CONT handling in the recording code was rather confusing too). This re-introduces a real semantically meaningful KERN_CONT, and fixes the few places I noticed where it was missing. There are probably more missing cases, since KERN_CONT hasn't actually had any semantic meaning for at least four years (other than the checkpatch meaning of "no log level necessary, this is a continuation line"). This also allows the combination of KERN_CONT and a log level. In that case the log level will be ignored if the merging with a previous line is successful, but if a new record is needed, that new record will now get the right log level. That also means that you can at least in theory combine KERN_CONT with the "pr_info()" style helpers, although any use of pr_fmt() prefixing would make that just result in a mess, of course (the prefix would end up in the middle of a continuing line). * printk-cleanups: printk: make reading the kernel log flush pending lines printk: re-organize log_output() to be more legible printk: split out core logging code into helper function printk: reinstate KERN_CONT for printing continuation lines
2016-10-09printk: make reading the kernel log flush pending linesLinus Torvalds1-0/+11
That will mean that any possible subsequent continuation will now be broken up onto a line of its own (since reading the log has finalized the beginning og the line), but if user space has activated system logging (or if there's a kernel message dump going on) that is the right thing to do. And now that we actually get the continuation flags _right_ for this all, the user space logger that is reading the kernel messages can actually see the continuation marker. Not that anybody seems to really bother with it (or care), but in theory user space can do its own message stitching. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-09printk: re-organize log_output() to be more legibleLinus Torvalds1-35/+27
Avoid some duplicate logic now that we can return early, and update the comments for the new LOG_CONT world order. This also stops the continuation flushing from just using random record flags for the flushing action, instead taking the flags from the proper original line and updating them as we add continuations to it. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-09printk: split out core logging code into helper functionLinus Torvalds1-39/+39
The code that actually decides how to log the message (whether to put it directly into the record log, whether to append it to an existing buffered log, or whether to start a new buffered log) is fairly non-obvious code in the middle of the vprintk_emit() function. Splitting that code up into a helper function makes it easier to understand, but perhaps more importantly also allows for the code to just return early out of the helper function once it has made the decision about where the new log content goes. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-09printk: reinstate KERN_CONT for printing continuation linesLinus Torvalds1-17/+12
Long long ago the kernel log buffer was a buffered stream of bytes, very much like stdio in user space. It supported log levels by scanning the stream and noticing the log level markers at the beginning of each line, but if you wanted to print a partial line in multiple chunks, you just did multiple printk() calls, and it just automatically worked. Except when it didn't, and you had very confusing output when different lines got all mixed up with each other. Then you got fragment lines mixing with each other, or with non-fragment lines, because it was traditionally impossible to tell whether a printk() call was a continuation or not. To at least help clarify the issue of continuation lines, we added a KERN_CONT marker back in 2007 to mark continuation lines: 474925277671 ("printk: add KERN_CONT annotation"). That continuation marker was initially an empty string, and didn't actuall make any semantic difference. But it at least made it possible to annotate the source code, and have check-patch notice that a printk() didn't need or want a log level marker, because it was a continuation of a previous line. To avoid the ambiguity between a continuation line that had that KERN_CONT marker, and a printk with no level information at all, we then in 2009 made KERN_CONT be a real log level marker which meant that we could now reliably tell the difference between the two cases. 5fd29d6ccbc9 ("printk: clean up handling of log-levels and newlines") and we could take advantage of that to make sure we didn't mix up continuation lines with lines that just didn't have any loglevel at all. Then, in 2012, the kernel log buffer was changed to be a "record" based log, where each line was a record that has a loglevel and a timestamp. You can see the beginning of that conversion in commits e11fea92e13f ("kmsg: export printk records to the /dev/kmsg interface") 7ff9554bb578 ("printk: convert byte-buffer to variable-length record buffer") with a number of follow-up commits to fix some painful fallout from that conversion. Over all, it took a couple of months to sort out most of it. But the upside was that you could have concurrent readers (and writers) of the kernel log and not have lines with mixed output in them. And one particular pain-point for the record-based kernel logging was exactly the fragmentary lines that are generated in smaller chunks. In order to still log them as one recrod, the continuation lines need to be attached to the previous record properly. However the explicit continuation record marker that is actually useful for this exact case was actually removed in aroundm the same time by commit 61e99ab8e35a ("printk: remove the now unnecessary "C" annotation for KERN_CONT") due to the incorrect belief that KERN_CONT wasn't meaningful. The ambiguity between "is this a continuation line" or "is this a plain printk with no log level information" was reintroduced, and in fact became an even bigger pain point because there was now the whole record-level merging of kernel messages going on. This patch reinstates the KERN_CONT as a real non-empty string marker, so that the ambiguity is fixed once again. But it's not a plain revert of that original removal: in the four years since we made KERN_CONT an empty string again, not only has the format of the log level markers changed, we've also had some usage changes in this area. For example, some ACPI code seems to use KERN_CONT _together_ with a log level, and now uses both the KERN_CONT marker and (for example) a KERN_INFO marker to show that it's an informational continuation of a line. Which is actually not a bad idea - if the continuation line cannot be attached to its predecessor, without the log level information we don't know what log level to assign to it (and we traditionally just assigned it the default loglevel). So having both a log level and the KERN_CONT marker is not necessarily a bad idea, but it does mean that we need to actually iterate over potentially multiple markers, rather than just a single one. Also, since KERN_CONT was still conceptually needed, and encouraged, but didn't actually _do_ anything, we've also had the reverse problem: rather than having too many annotations it has too few, and there is bit rot with code that no longer marks the continuation lines with the KERN_CONT marker. So this patch not only re-instates the non-empty KERN_CONT marker, it also fixes up the cases of bit-rot I noticed in my own logs. There are probably other cases where KERN_CONT will be needed to be added, either because it is new code that never dealt with the need for KERN_CONT, or old code that has bitrotted without anybody noticing. That said, we should strive to avoid the need for KERN_CONT. It does result in real problems for logging, and should generally not be seen as a good feature. If we some day can get rid of the feature entirely, because nobody does any fragmented printk calls, that would be lovely. But until that point, let's at mark the code that relies on the hacky multi-fragment kernel printk's. Not only does it avoid the ambiguity, it also annotates code as "maybe this would be good to fix some day". (That said, particularly during single-threaded bootup, the downsides of KERN_CONT are very limited. Things get much hairier when you have multiple threads going on and user level reading and writing logs too). Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-07console: don't prefer first registered if DT specifies stdout-pathPaul Burton1-1/+12
If a device tree specifies a preferred device for kernel console output via the stdout-path or linux,stdout-path chosen node properties or the stdout alias then the kernel ought to honor it & output the kernel console to that device. As it stands, this isn't the case. Whilst we parse the stdout-path properties & set an of_stdout variable from of_alias_scan(), and use that from of_console_check() to determine whether to add a console device as a preferred console whilst registering it, we also prefer the first registered console if no other has been selected at the time of its registration. This means that if a console other than the one the device tree selects via stdout-path is registered first, we will switch to using it & when the stdout-path console is later registered the call to add_preferred_console() via of_console_check() is too late to do anything useful. In practice this seems to mean that we switch to the dummy console device fairly early & see no further console output: Console: colour dummy device 80x25 console [tty0] enabled bootconsole [ns16550a0] disabled Fix this by not automatically preferring the first registered console if one is specified by the device tree. This allows consoles to be registered but not enabled, and once the driver for the console selected by stdout-path calls of_console_check() the driver will be added to the list of preferred consoles before any other console has been enabled. When that console is then registered via register_console() it will be enabled as expected. Link: http://lkml.kernel.org/r/20160809151937.26118-1-paul.burton@imgtec.com Signed-off-by: Paul Burton <paul.burton@imgtec.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Tejun Heo <tj@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Ivan Delalande <colona@arista.com> Cc: Thierry Reding <treding@nvidia.com> Cc: Borislav Petkov <bp@suse.de> Cc: Jan Kara <jack@suse.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Joe Perches <joe@perches.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Rob Herring <robh+dt@kernel.org> Cc: Frank Rowand <frowand.list@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-09-01printk/nmi: avoid direct printk()-s from __printk_nmi_flush()Sergey Senozhatsky1-15/+23
__printk_nmi_flush() can be called from nmi_panic(), therefore it has to test whether it's executed in NMI context and thus must route the messages through deferred printk() or via direct printk(). This is to avoid potential deadlocks, as described in commit cf9b1106c81c ("printk/nmi: flush NMI messages on the system panic"). However there remain two places where __printk_nmi_flush() does unconditional direct printk() calls: - pr_err("printk_nmi_flush: internal error ...") - pr_cont("\n") Factor out print_nmi_seq_line() parts into a new printk_nmi_flush_line() function, which takes care of in_nmi(), and use it in __printk_nmi_flush() for printing and error-reporting. Link: http://lkml.kernel.org/r/20160830161354.581-1-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-26printk: fix parsing of "brl=" optionNicolas Iooss1-2/+2
Commit bbeddf52adc1 ("printk: move braille console support into separate braille.[ch] files") moved the parsing of braille-related options into _braille_console_setup(), changing the type of variable str from char* to char**. In this commit, memcmp(str, "brl,", 4) was correctly updated to memcmp(*str, "brl,", 4) but not memcmp(str, "brl=", 4). Update the code to make "brl=" option work again and replace memcmp() with strncmp() to make the compiler able to detect such an issue. Fixes: bbeddf52adc1 ("printk: move braille console support into separate braille.[ch] files") Link: http://lkml.kernel.org/r/20160823165700.28952-1-nicolas.iooss_linux@m4x.org Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-09Revert "printk: create pr_<level> functions"Linus Torvalds3-43/+11
This reverts commit 874f9c7da9a4acbc1b9e12ca722579fb50e4d142. Geert Uytterhoeven reports: "This change seems to have an (unintendent?) side-effect. Before, pr_*() calls without a trailing newline characters would be printed with a newline character appended, both on the console and in the output of the dmesg command. After this commit, no new line character is appended, and the output of the next pr_*() call of the same type may be appended, like in: - Truncating RAM at 0x0000000040000000-0x00000000c0000000 to -0x0000000070000000 - Ignoring RAM at 0x0000000200000000-0x0000000240000000 (!CONFIG_HIGHMEM) + Truncating RAM at 0x0000000040000000-0x00000000c0000000 to -0x0000000070000000Ignoring RAM at 0x0000000200000000-0x0000000240000000 (!CONFIG_HIGHMEM)" Joe Perches says: "No, that is not intentional. The newline handling code inside vprintk_emit is a bit involved and for now I suggest a revert until this has all the same behavior as earlier" Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Requested-by: Joe Perches <joe@perches.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-08printk: Remove unnecessary #ifdef CONFIG_PRINTKAndreas Ziegler1-2/+0
In commit 874f9c7da9a4 ("printk: create pr_<level> functions"), new pr_level defines were added to printk.c. These new defines are guarded by an #ifdef CONFIG_PRINTK - however, there is already a surrounding #ifdef CONFIG_PRINTK starting a lot earlier in line 249 which means the newly introduced #ifdef is unnecessary. Let's remove it to avoid confusion. Signed-off-by: Andreas Ziegler <andreas.ziegler@fau.de> Cc: Joe Perches <joe@perches.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02printk: add kernel parameter to control writes to /dev/kmsgBorislav Petkov1-8/+134
Add a "printk.devkmsg" kernel command line parameter which controls how userspace writes into /dev/kmsg. It has three options: * ratelimit - ratelimit logging from userspace. * on - unlimited logging from userspace * off - logging from userspace gets ignored The default setting is to ratelimit the messages written to it. This changes the kernel default setting of "on" to "ratelimit" and we do that because we want to keep userspace spamming /dev/kmsg to sane levels. This is especially moot when a small kernel log buffer wraps around and messages get lost. So the ratelimiting setting should be a sane setting where kernel messages should have a bit higher chance of survival from all the spamming. It additionally does not limit logging to /dev/kmsg while the system is booting if we haven't disabled it on the command line. Furthermore, we can control the logging from a lower priority sysctl interface - kernel.printk_devkmsg. That interface will succeed only if printk.devkmsg *hasn't* been supplied on the command line. If it has, then printk.devkmsg is a one-time setting which remains for the duration of the system lifetime. This "locking" of the setting is to prevent userspace from changing the logging on us through sysctl(2). This patch is based on previous patches from Linus and Steven. [bp@suse.de: fixes] Link: http://lkml.kernel.org/r/20160719072344.GC25563@nazgul.tnic Link: http://lkml.kernel.org/r/20160716061745.15795-3-bp@alien8.de Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Dave Young <dyoung@redhat.com> Cc: Franck Bui <fbui@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02printk: include <asm/sections.h> instead of <asm-generic/sections.h>Christoph Hellwig1-1/+1
asm-generic headers are generic implementations for architecture specific code and should not be included by common code. Thus use the asm/ version of sections.h to get at the linker sections. Link: http://lkml.kernel.org/r/1468285008-7331-1-git-send-email-hch@lst.de Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02printk: introduce suppress_message_printing()Sergey Senozhatsky1-6/+19
Messages' levels and console log level are inspected when the actual printing occurs, which may provoke console_unlock() and console_cont_flush() to waste CPU cycles on every message that has loglevel above the current console_loglevel. Schematically, console_unlock() does the following: console_unlock() { ... for (;;) { ... raw_spin_lock_irqsave(&logbuf_lock, flags); skip: msg = log_from_idx(console_idx); if (msg->flags & LOG_NOCONS) { ... goto skip; } level = msg->level; len += msg_print_text(); >> sprintfs memcpy, etc. if (nr_ext_console_drivers) { ext_len = msg_print_ext_header(); >> scnprintf ext_len += msg_print_ext_body(); >> scnprintfs etc. } ... raw_spin_unlock(&logbuf_lock); call_console_drivers(level, ext_text, ext_len, text, len) { if (level >= console_loglevel && >> drop the message !ignore_loglevel) return; console->write(...); } local_irq_restore(flags); } ... } The thing here is this deferred `level >= console_loglevel' check. We are wasting CPU cycles on sprintfs/memcpy/etc. preparing the messages that we will eventually drop. This can be huge when we register a new CON_PRINTBUFFER console, for instance. For every such a console register_console() resets the console_seq, console_idx, console_prev and sets a `exclusive console' pointer to replay the log buffer to that just-registered console. And there can be a lot of messages to replay, in the worst case most of which can be dropped after console_loglevel test. We know messages' levels long before we call msg_print_text() and friends, so we can just move console_loglevel check out of call_console_drivers() and format a new message only if we are sure that it won't be dropped. The patch factors out loglevel check into suppress_message_printing() function and tests message->level and console_loglevel before formatting functions in console_unlock() and console_cont_flush() are getting executed. This improves things not only for exclusive CON_PRINTBUFFER consoles, but for every console_unlock() that attempts to print a message of level above the console_loglevel. Link: http://lkml.kernel.org/r/20160627135012.8229-1-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Cc: Tejun Heo <tj@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Calvin Owens <calvinowens@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02printk: create pr_<level> functionsJoe Perches3-11/+45
Using functions instead of macros can reduce overall code size by eliminating unnecessary "KERN_SOH<digit>" prefixes from format strings. defconfig x86-64: $ size vmlinux* text data bss dec hex filename 10193570 4331464 1105920 15630954 ee826a vmlinux.new 10192623 4335560 1105920 15634103 ee8eb7 vmlinux.old As the return value are unimportant and unused in the kernel tree, these new functions return void. Miscellanea: - change pr_<level> macros to call new __pr_<level> functions - change vprintk_nmi and vprintk_default to add LOGLEVEL_<level> argument [akpm@linux-foundation.org: fix LOGLEVEL_INFO, per Joe] Link: http://lkml.kernel.org/r/e16cc34479dfefcae37c98b481e6646f0f69efc3.1466718827.git.joe@perches.com Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02printk: do not include interrupt.hSergey Senozhatsky1-1/+0
A trivial cosmetic change: interrupt.h header is redundant since commit 6b898c07cb1d ("console: use might_sleep in console_lock"). Link: http://lkml.kernel.org/r/20160620132847.21930-1-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-28printk: when dumping regs, show the stack, not thread_infoAndy Lutomirski1-3/+2
We currently show: task: <current> ti: <current_thread_info()> task.ti: <task_thread_info(current)>" "ti" and "task.ti" are redundant, and neither is actually what we want to show, which the the base of the thread stack. Change the display to show the stack pointer explicitly. Link: http://lkml.kernel.org/r/543ac5bd66ff94000a57a02e11af7239571a3055.1468523549.git.luto@kernel.org Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20printk/nmi: flush NMI messages on the system panicPetr Mladek3-2/+41
In NMI context, printk() messages are stored into per-CPU buffers to avoid a possible deadlock. They are normally flushed to the main ring buffer via an IRQ work. But the work is never called when the system calls panic() in the very same NMI handler. This patch tries to flush NMI buffers before the crash dump is generated. In this case it does not risk a double release and bails out when the logbuf_lock is already taken. The aim is to get the messages into the main ring buffer when possible. It makes them better accessible in the vmcore. Then the patch tries to flush the buffers second time when other CPUs are down. It might be more aggressive and reset logbuf_lock. The aim is to get the messages available for the consequent kmsg_dump() and console_flush_on_panic() calls. The patch causes vprintk_emit() to be called even in NMI context again. But it is done via printk_deferred() so that the console handling is skipped. Consoles use internal locks and we could not prevent a deadlock easily. They are explicitly called later when the crash dump is not generated, see console_flush_on_panic(). Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: David Miller <davem@davemloft.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jiri Kosina <jkosina@suse.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20printk/nmi: increase the size of NMI buffer and make it configurablePetr Mladek1-1/+2
Testing has shown that the backtrace sometimes does not fit into the 4kB temporary buffer that is used in NMI context. The warnings are gone when I double the temporary buffer size. This patch doubles the buffer size and makes it configurable. Note that this problem existed even in the x86-specific implementation that was added by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack trace on all CPUs"). Nobody noticed it because it did not print any warnings. Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Jan Kara <jack@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: Jiri Kosina <jkosina@suse.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: David Miller <davem@davemloft.net> Cc: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20printk/nmi: warn when some message has been lost in NMI contextPetr Mladek3-1/+25
We could not resize the temporary buffer in NMI context. Let's warn if a message is lost. This is rather theoretical. printk() should not be used in NMI. The only sensible use is when we want to print backtrace from all CPUs. The current buffer should be enough for this purpose. [akpm@linux-foundation.org: whitespace fixlet] Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Jan Kara <jack@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: Jiri Kosina <jkosina@suse.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: David Miller <davem@davemloft.net> Cc: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-20printk/nmi: generic solution for safe printk in NMIPetr Mladek4-18/+265
printk() takes some locks and could not be used a safe way in NMI context. The chance of a deadlock is real especially when printing stacks from all CPUs. This particular problem has been addressed on x86 by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack trace on all CPUs"). The patchset brings two big advantages. First, it makes the NMI backtraces safe on all architectures for free. Second, it makes all NMI messages almost safe on all architectures (the temporary buffer is limited. We still should keep the number of messages in NMI context at minimum). Note that there already are several messages printed in NMI context: WARN_ON(in_nmi()), BUG_ON(in_nmi()), anything being printed out from MCE handlers. These are not easy to avoid. This patch reuses most of the code and makes it generic. It is useful for all messages and architectures that support NMI. The alternative printk_func is set when entering and is reseted when leaving NMI context. It queues IRQ work to copy the messages into the main ring buffer in a safe context. __printk_nmi_flush() copies all available messages and reset the buffer. Then we could use a simple cmpxchg operations to get synchronized with writers. There is also used a spinlock to get synchronized with other flushers. We do not longer use seq_buf because it depends on external lock. It would be hard to make all supported operations safe for a lockless use. It would be confusing and error prone to make only some operations safe. The code is put into separate printk/nmi.c as suggested by Steven Rostedt. It needs a per-CPU buffer and is compiled only on architectures that call nmi_enter(). This is achieved by the new HAVE_NMI Kconfig flag. The are MN10300 and Xtensa architectures. We need to clean up NMI handling there first. Let's do it separately. The patch is heavily based on the draft from Peter Zijlstra, see https://lkml.org/lkml/2015/6/10/327 [arnd@arndb.de: printk-nmi: use %zu format string for size_t] [akpm@linux-foundation.org: min_t->min - all types are size_t here] Signed-off-by: Petr Mladek <pmladek@suse.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Cc: Jan Kara <jack@suse.cz> Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> [arm part] Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: Jiri Kosina <jkosina@suse.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: David Miller <davem@davemloft.net> Cc: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-17printk: add clear_idx symbol to vmcoreinfoIvan Delalande1-10/+9
This allows us to extract from the vmcore only the messages emitted since the last time the ring buffer was cleared. We just have to make sure its value is always up-to-date, when old messages are discarded to free space in log_make_free_space() for example. Signed-off-by: Zeyu Zhao <zzy8200@gmail.com> Signed-off-by: Ivan Delalande <colona@arista.com> Cc: Kay Sievers <kay@vrfy.org> Cc: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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