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authorPetr Mladek <pmladek@suse.com>2022-06-23 19:11:28 +0200
committerPetr Mladek <pmladek@suse.com>2022-06-23 19:11:28 +0200
commit51889d225ce2ce118d8413eb4282045add81a689 (patch)
tree90266007a2a99150c9870c0df9ec14288f2ba7cc /kernel
parent93d17c1c8c1cc987aad378d5266d99e46efca43c (diff)
parent07a22b61946f0b80065b0ddcc703b715f84355f5 (diff)
downloadlinux-51889d225ce2ce118d8413eb4282045add81a689.tar.bz2
Merge branch 'rework/kthreads' into for-linus
Diffstat (limited to 'kernel')
-rw-r--r--kernel/hung_task.c11
-rw-r--r--kernel/panic.c6
-rw-r--r--kernel/printk/internal.h2
-rw-r--r--kernel/printk/printk.c593
-rw-r--r--kernel/printk/printk_safe.c32
-rw-r--r--kernel/rcu/tree_stall.h2
-rw-r--r--kernel/reboot.c16
-rw-r--r--kernel/watchdog.c4
-rw-r--r--kernel/watchdog_hld.c4
9 files changed, 65 insertions, 605 deletions
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 80bfea5dd5c4..cff3ae8c818f 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -127,8 +127,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
* complain:
*/
if (sysctl_hung_task_warnings) {
- printk_prefer_direct_enter();
-
if (sysctl_hung_task_warnings > 0)
sysctl_hung_task_warnings--;
pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
@@ -144,8 +142,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
if (sysctl_hung_task_all_cpu_backtrace)
hung_task_show_all_bt = true;
-
- printk_prefer_direct_exit();
}
touch_nmi_watchdog();
@@ -208,17 +204,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
}
unlock:
rcu_read_unlock();
- if (hung_task_show_lock) {
- printk_prefer_direct_enter();
+ if (hung_task_show_lock)
debug_show_all_locks();
- printk_prefer_direct_exit();
- }
if (hung_task_show_all_bt) {
hung_task_show_all_bt = false;
- printk_prefer_direct_enter();
trigger_all_cpu_backtrace();
- printk_prefer_direct_exit();
}
if (hung_task_call_panic)
diff --git a/kernel/panic.c b/kernel/panic.c
index 4cf13c37bd08..a3308af28a21 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -297,7 +297,6 @@ void panic(const char *fmt, ...)
* unfortunately means it may not be hardened to work in a
* panic situation.
*/
- try_block_console_kthreads(10000);
smp_send_stop();
} else {
/*
@@ -305,7 +304,6 @@ void panic(const char *fmt, ...)
* kmsg_dump, we will need architecture dependent extra
* works in addition to stopping other CPUs.
*/
- try_block_console_kthreads(10000);
crash_smp_send_stop();
}
@@ -605,8 +603,6 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
{
disable_trace_on_warning();
- printk_prefer_direct_enter();
-
if (file)
pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
raw_smp_processor_id(), current->pid, file, line,
@@ -636,8 +632,6 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
/* Just a warning, don't kill lockdep. */
add_taint(taint, LOCKDEP_STILL_OK);
-
- printk_prefer_direct_exit();
}
#ifndef __WARN_FLAGS
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index e7d8578860ad..d947ca6c84f9 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -20,8 +20,6 @@ enum printk_info_flags {
LOG_CONT = 8, /* text is a fragment of a continuation line */
};
-extern bool block_console_kthreads;
-
__printf(4, 0)
int vprintk_store(int facility, int level,
const struct dev_printk_info *dev_info,
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index b095fb5f5f61..b49c6ff6dca0 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -224,36 +224,6 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
static int nr_ext_console_drivers;
/*
- * Used to synchronize printing kthreads against direct printing via
- * console_trylock/console_unlock.
- *
- * Values:
- * -1 = console kthreads atomically blocked (via global trylock)
- * 0 = no kthread printing, console not locked (via trylock)
- * >0 = kthread(s) actively printing
- *
- * Note: For synchronizing against direct printing via
- * console_lock/console_unlock, see the @lock variable in
- * struct console.
- */
-static atomic_t console_kthreads_active = ATOMIC_INIT(0);
-
-#define console_kthreads_atomic_tryblock() \
- (atomic_cmpxchg(&console_kthreads_active, 0, -1) == 0)
-#define console_kthreads_atomic_unblock() \
- atomic_cmpxchg(&console_kthreads_active, -1, 0)
-#define console_kthreads_atomically_blocked() \
- (atomic_read(&console_kthreads_active) == -1)
-
-#define console_kthread_printing_tryenter() \
- atomic_inc_unless_negative(&console_kthreads_active)
-#define console_kthread_printing_exit() \
- atomic_dec(&console_kthreads_active)
-
-/* Block console kthreads to avoid processing new messages. */
-bool block_console_kthreads;
-
-/*
* Helper macros to handle lockdep when locking/unlocking console_sem. We use
* macros instead of functions so that _RET_IP_ contains useful information.
*/
@@ -301,49 +271,14 @@ static bool panic_in_progress(void)
}
/*
- * Tracks whether kthread printers are all blocked. A value of true implies
- * that the console is locked via console_lock() or the console is suspended.
- * Writing to this variable requires holding @console_sem.
+ * This is used for debugging the mess that is the VT code by
+ * keeping track if we have the console semaphore held. It's
+ * definitely not the perfect debug tool (we don't know if _WE_
+ * hold it and are racing, but it helps tracking those weird code
+ * paths in the console code where we end up in places I want
+ * locked without the console semaphore held).
*/
-static bool console_kthreads_blocked;
-
-/*
- * Block all kthread printers from a schedulable context.
- *
- * Requires holding @console_sem.
- */
-static void console_kthreads_block(void)
-{
- struct console *con;
-
- for_each_console(con) {
- mutex_lock(&con->lock);
- con->blocked = true;
- mutex_unlock(&con->lock);
- }
-
- console_kthreads_blocked = true;
-}
-
-/*
- * Unblock all kthread printers from a schedulable context.
- *
- * Requires holding @console_sem.
- */
-static void console_kthreads_unblock(void)
-{
- struct console *con;
-
- for_each_console(con) {
- mutex_lock(&con->lock);
- con->blocked = false;
- mutex_unlock(&con->lock);
- }
-
- console_kthreads_blocked = false;
-}
-
-static int console_suspended;
+static int console_locked, console_suspended;
/*
* Array of consoles built from command line options (console=)
@@ -426,75 +361,7 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
/* syslog_lock protects syslog_* variables and write access to clear_seq. */
static DEFINE_MUTEX(syslog_lock);
-/*
- * A flag to signify if printk_activate_kthreads() has already started the
- * kthread printers. If true, any later registered consoles must start their
- * own kthread directly. The flag is write protected by the console_lock.
- */
-static bool printk_kthreads_available;
-
#ifdef CONFIG_PRINTK
-static atomic_t printk_prefer_direct = ATOMIC_INIT(0);
-
-/**
- * printk_prefer_direct_enter - cause printk() calls to attempt direct
- * printing to all enabled consoles
- *
- * Since it is not possible to call into the console printing code from any
- * context, there is no guarantee that direct printing will occur.
- *
- * This globally effects all printk() callers.
- *
- * Context: Any context.
- */
-void printk_prefer_direct_enter(void)
-{
- atomic_inc(&printk_prefer_direct);
-}
-
-/**
- * printk_prefer_direct_exit - restore printk() behavior
- *
- * Context: Any context.
- */
-void printk_prefer_direct_exit(void)
-{
- WARN_ON(atomic_dec_if_positive(&printk_prefer_direct) < 0);
-}
-
-/*
- * Calling printk() always wakes kthread printers so that they can
- * flush the new message to their respective consoles. Also, if direct
- * printing is allowed, printk() tries to flush the messages directly.
- *
- * Direct printing is allowed in situations when the kthreads
- * are not available or the system is in a problematic state.
- *
- * See the implementation about possible races.
- */
-static inline bool allow_direct_printing(void)
-{
- /*
- * Checking kthread availability is a possible race because the
- * kthread printers can become permanently disabled during runtime.
- * However, doing that requires holding the console_lock, so any
- * pending messages will be direct printed by console_unlock().
- */
- if (!printk_kthreads_available)
- return true;
-
- /*
- * Prefer direct printing when the system is in a problematic state.
- * The context that sets this state will always see the updated value.
- * The other contexts do not care. Anyway, direct printing is just a
- * best effort. The direct output is only possible when console_lock
- * is not already taken and no kthread printers are actively printing.
- */
- return (system_state > SYSTEM_RUNNING ||
- oops_in_progress ||
- atomic_read(&printk_prefer_direct));
-}
-
DECLARE_WAIT_QUEUE_HEAD(log_wait);
/* All 3 protected by @syslog_lock. */
/* the next printk record to read by syslog(READ) or /proc/kmsg */
@@ -2385,10 +2252,10 @@ asmlinkage int vprintk_emit(int facility, int level,
printed_len = vprintk_store(facility, level, dev_info, fmt, args);
/* If called from the scheduler, we can not call up(). */
- if (!in_sched && allow_direct_printing()) {
+ if (!in_sched) {
/*
* The caller may be holding system-critical or
- * timing-sensitive locks. Disable preemption during direct
+ * timing-sensitive locks. Disable preemption during
* printing of all remaining records to all consoles so that
* this context can return as soon as possible. Hopefully
* another printk() caller will take over the printing.
@@ -2431,8 +2298,6 @@ EXPORT_SYMBOL(_printk);
static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
-static void printk_start_kthread(struct console *con);
-
#else /* CONFIG_PRINTK */
#define CONSOLE_LOG_MAX 0
@@ -2466,8 +2331,6 @@ static void call_console_driver(struct console *con, const char *text, size_t le
}
static bool suppress_message_printing(int level) { return false; }
static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
-static void printk_start_kthread(struct console *con) { }
-static bool allow_direct_printing(void) { return true; }
#endif /* CONFIG_PRINTK */
@@ -2686,14 +2549,6 @@ static int console_cpu_notify(unsigned int cpu)
/* If trylock fails, someone else is doing the printing */
if (console_trylock())
console_unlock();
- else {
- /*
- * If a new CPU comes online, the conditions for
- * printer_should_wake() may have changed for some
- * kthread printer with !CON_ANYTIME.
- */
- wake_up_klogd();
- }
}
return 0;
}
@@ -2713,7 +2568,7 @@ void console_lock(void)
down_console_sem();
if (console_suspended)
return;
- console_kthreads_block();
+ console_locked = 1;
console_may_schedule = 1;
}
EXPORT_SYMBOL(console_lock);
@@ -2734,30 +2589,15 @@ int console_trylock(void)
up_console_sem();
return 0;
}
- if (!console_kthreads_atomic_tryblock()) {
- up_console_sem();
- return 0;
- }
+ console_locked = 1;
console_may_schedule = 0;
return 1;
}
EXPORT_SYMBOL(console_trylock);
-/*
- * This is used to help to make sure that certain paths within the VT code are
- * running with the console lock held. It is definitely not the perfect debug
- * tool (it is not known if the VT code is the task holding the console lock),
- * but it helps tracking those weird code paths in the console code such as
- * when the console is suspended: where the console is not locked but no
- * console printing may occur.
- *
- * Note: This returns true when the console is suspended but is not locked.
- * This is intentional because the VT code must consider that situation
- * the same as if the console was locked.
- */
int is_console_locked(void)
{
- return (console_kthreads_blocked || atomic_read(&console_kthreads_active));
+ return console_locked;
}
EXPORT_SYMBOL(is_console_locked);
@@ -2780,9 +2620,18 @@ static bool abandon_console_lock_in_panic(void)
return atomic_read(&panic_cpu) != raw_smp_processor_id();
}
-static inline bool __console_is_usable(short flags)
+/*
+ * Check if the given console is currently capable and allowed to print
+ * records.
+ *
+ * Requires the console_lock.
+ */
+static inline bool console_is_usable(struct console *con)
{
- if (!(flags & CON_ENABLED))
+ if (!(con->flags & CON_ENABLED))
+ return false;
+
+ if (!con->write)
return false;
/*
@@ -2791,43 +2640,15 @@ static inline bool __console_is_usable(short flags)
* cope (CON_ANYTIME) don't call them until this CPU is officially up.
*/
if (!cpu_online(raw_smp_processor_id()) &&
- !(flags & CON_ANYTIME))
+ !(con->flags & CON_ANYTIME))
return false;
return true;
}
-/*
- * Check if the given console is currently capable and allowed to print
- * records.
- *
- * Requires holding the console_lock.
- */
-static inline bool console_is_usable(struct console *con)
-{
- if (!con->write)
- return false;
-
- return __console_is_usable(con->flags);
-}
-
static void __console_unlock(void)
{
- /*
- * Depending on whether console_lock() or console_trylock() was used,
- * appropriately allow the kthread printers to continue.
- */
- if (console_kthreads_blocked)
- console_kthreads_unblock();
- else
- console_kthreads_atomic_unblock();
-
- /*
- * New records may have arrived while the console was locked.
- * Wake the kthread printers to print them.
- */
- wake_up_klogd();
-
+ console_locked = 0;
up_console_sem();
}
@@ -2845,19 +2666,17 @@ static void __console_unlock(void)
*
* @handover will be set to true if a printk waiter has taken over the
* console_lock, in which case the caller is no longer holding the
- * console_lock. Otherwise it is set to false. A NULL pointer may be provided
- * to disable allowing the console_lock to be taken over by a printk waiter.
+ * console_lock. Otherwise it is set to false.
*
* Returns false if the given console has no next record to print, otherwise
* true.
*
- * Requires the console_lock if @handover is non-NULL.
- * Requires con->lock otherwise.
+ * Requires the console_lock.
*/
-static bool __console_emit_next_record(struct console *con, char *text, char *ext_text,
- char *dropped_text, bool *handover)
+static bool console_emit_next_record(struct console *con, char *text, char *ext_text,
+ char *dropped_text, bool *handover)
{
- static atomic_t panic_console_dropped = ATOMIC_INIT(0);
+ static int panic_console_dropped;
struct printk_info info;
struct printk_record r;
unsigned long flags;
@@ -2866,8 +2685,7 @@ static bool __console_emit_next_record(struct console *con, char *text, char *ex
prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX);
- if (handover)
- *handover = false;
+ *handover = false;
if (!prb_read_valid(prb, con->seq, &r))
return false;
@@ -2875,8 +2693,7 @@ static bool __console_emit_next_record(struct console *con, char *text, char *ex
if (con->seq != r.info->seq) {
con->dropped += r.info->seq - con->seq;
con->seq = r.info->seq;
- if (panic_in_progress() &&
- atomic_fetch_inc_relaxed(&panic_console_dropped) > 10) {
+ if (panic_in_progress() && panic_console_dropped++ > 10) {
suppress_panic_printk = 1;
pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n");
}
@@ -2898,62 +2715,32 @@ static bool __console_emit_next_record(struct console *con, char *text, char *ex
len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time);
}
- if (handover) {
- /*
- * While actively printing out messages, if another printk()
- * were to occur on another CPU, it may wait for this one to
- * finish. This task can not be preempted if there is a
- * waiter waiting to take over.
- *
- * Interrupts are disabled because the hand over to a waiter
- * must not be interrupted until the hand over is completed
- * (@console_waiter is cleared).
- */
- printk_safe_enter_irqsave(flags);
- console_lock_spinning_enable();
-
- /* don't trace irqsoff print latency */
- stop_critical_timings();
- }
+ /*
+ * While actively printing out messages, if another printk()
+ * were to occur on another CPU, it may wait for this one to
+ * finish. This task can not be preempted if there is a
+ * waiter waiting to take over.
+ *
+ * Interrupts are disabled because the hand over to a waiter
+ * must not be interrupted until the hand over is completed
+ * (@console_waiter is cleared).
+ */
+ printk_safe_enter_irqsave(flags);
+ console_lock_spinning_enable();
+ stop_critical_timings(); /* don't trace print latency */
call_console_driver(con, write_text, len, dropped_text);
+ start_critical_timings();
con->seq++;
- if (handover) {
- start_critical_timings();
- *handover = console_lock_spinning_disable_and_check();
- printk_safe_exit_irqrestore(flags);
- }
+ *handover = console_lock_spinning_disable_and_check();
+ printk_safe_exit_irqrestore(flags);
skip:
return true;
}
/*
- * Print a record for a given console, but allow another printk() caller to
- * take over the console_lock and continue printing.
- *
- * Requires the console_lock, but depending on @handover after the call, the
- * caller may no longer have the console_lock.
- *
- * See __console_emit_next_record() for argument and return details.
- */
-static bool console_emit_next_record_transferable(struct console *con, char *text, char *ext_text,
- char *dropped_text, bool *handover)
-{
- /*
- * Handovers are only supported if threaded printers are atomically
- * blocked. The context taking over the console_lock may be atomic.
- */
- if (!console_kthreads_atomically_blocked()) {
- *handover = false;
- handover = NULL;
- }
-
- return __console_emit_next_record(con, text, ext_text, dropped_text, handover);
-}
-
-/*
* Print out all remaining records to all consoles.
*
* @do_cond_resched is set by the caller. It can be true only in schedulable
@@ -2971,8 +2758,8 @@ static bool console_emit_next_record_transferable(struct console *con, char *tex
* were flushed to all usable consoles. A returned false informs the caller
* that everything was not flushed (either there were no usable consoles or
* another context has taken over printing or it is a panic situation and this
- * is not the panic CPU or direct printing is not preferred). Regardless the
- * reason, the caller should assume it is not useful to immediately try again.
+ * is not the panic CPU). Regardless the reason, the caller should assume it
+ * is not useful to immediately try again.
*
* Requires the console_lock.
*/
@@ -2989,10 +2776,6 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
*handover = false;
do {
- /* Let the kthread printers do the work if they can. */
- if (!allow_direct_printing())
- return false;
-
any_progress = false;
for_each_console(con) {
@@ -3004,11 +2787,13 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
if (con->flags & CON_EXTENDED) {
/* Extended consoles do not print "dropped messages". */
- progress = console_emit_next_record_transferable(con, &text[0],
- &ext_text[0], NULL, handover);
+ progress = console_emit_next_record(con, &text[0],
+ &ext_text[0], NULL,
+ handover);
} else {
- progress = console_emit_next_record_transferable(con, &text[0],
- NULL, &dropped_text[0], handover);
+ progress = console_emit_next_record(con, &text[0],
+ NULL, &dropped_text[0],
+ handover);
}
if (*handover)
return false;
@@ -3123,13 +2908,10 @@ void console_unblank(void)
if (oops_in_progress) {
if (down_trylock_console_sem() != 0)
return;
- if (!console_kthreads_atomic_tryblock()) {
- up_console_sem();
- return;
- }
} else
console_lock();
+ console_locked = 1;
console_may_schedule = 0;
for_each_console(c)
if ((c->flags & CON_ENABLED) && c->unblank)
@@ -3408,10 +3190,6 @@ void register_console(struct console *newcon)
nr_ext_console_drivers++;
newcon->dropped = 0;
- newcon->thread = NULL;
- newcon->blocked = true;
- mutex_init(&newcon->lock);
-
if (newcon->flags & CON_PRINTBUFFER) {
/* Get a consistent copy of @syslog_seq. */
mutex_lock(&syslog_lock);
@@ -3421,10 +3199,6 @@ void register_console(struct console *newcon)
/* Begin with next message. */
newcon->seq = prb_next_seq(prb);
}
-
- if (printk_kthreads_available)
- printk_start_kthread(newcon);
-
console_unlock();
console_sysfs_notify();
@@ -3451,7 +3225,6 @@ EXPORT_SYMBOL(register_console);
int unregister_console(struct console *console)
{
- struct task_struct *thd;
struct console *con;
int res;
@@ -3492,20 +3265,7 @@ int unregister_console(struct console *console)
console_drivers->flags |= CON_CONSDEV;
console->flags &= ~CON_ENABLED;
-
- /*
- * console->thread can only be cleared under the console lock. But
- * stopping the thread must be done without the console lock. The
- * task that clears @thread is the task that stops the kthread.
- */
- thd = console->thread;
- console->thread = NULL;
-
console_unlock();
-
- if (thd)
- kthread_stop(thd);
-
console_sysfs_notify();
if (console->exit)
@@ -3601,20 +3361,6 @@ static int __init printk_late_init(void)
}
late_initcall(printk_late_init);
-static int __init printk_activate_kthreads(void)
-{
- struct console *con;
-
- console_lock();
- printk_kthreads_available = true;
- for_each_console(con)
- printk_start_kthread(con);
- console_unlock();
-
- return 0;
-}
-early_initcall(printk_activate_kthreads);
-
#if defined CONFIG_PRINTK
/* If @con is specified, only wait for that console. Otherwise wait for all. */
static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress)
@@ -3689,209 +3435,11 @@ bool pr_flush(int timeout_ms, bool reset_on_progress)
}
EXPORT_SYMBOL(pr_flush);
-static void __printk_fallback_preferred_direct(void)
-{
- printk_prefer_direct_enter();
- pr_err("falling back to preferred direct printing\n");
- printk_kthreads_available = false;
-}
-
-/*
- * Enter preferred direct printing, but never exit. Mark console threads as
- * unavailable. The system is then forever in preferred direct printing and
- * any printing threads will exit.
- *
- * Must *not* be called under console_lock. Use
- * __printk_fallback_preferred_direct() if already holding console_lock.
- */
-static void printk_fallback_preferred_direct(void)
-{
- console_lock();
- __printk_fallback_preferred_direct();
- console_unlock();
-}
-
-/*
- * Print a record for a given console, not allowing another printk() caller
- * to take over. This is appropriate for contexts that do not have the
- * console_lock.
- *
- * See __console_emit_next_record() for argument and return details.
- */
-static bool console_emit_next_record(struct console *con, char *text, char *ext_text,
- char *dropped_text)
-{
- return __console_emit_next_record(con, text, ext_text, dropped_text, NULL);
-}
-
-static bool printer_should_wake(struct console *con, u64 seq)
-{
- short flags;
-
- if (kthread_should_stop() || !printk_kthreads_available)
- return true;
-
- if (con->blocked ||
- console_kthreads_atomically_blocked() ||
- block_console_kthreads ||
- system_state > SYSTEM_RUNNING ||
- oops_in_progress) {
- return false;
- }
-
- /*
- * This is an unsafe read from con->flags, but a false positive is
- * not a problem. Worst case it would allow the printer to wake up
- * although it is disabled. But the printer will notice that when
- * attempting to print and instead go back to sleep.
- */
- flags = data_race(READ_ONCE(con->flags));
-
- if (!__console_is_usable(flags))
- return false;
-
- return prb_read_valid(prb, seq, NULL);
-}
-
-static int printk_kthread_func(void *data)
-{
- struct console *con = data;
- char *dropped_text = NULL;
- char *ext_text = NULL;
- u64 seq = 0;
- char *text;
- int error;
-
- text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL);
- if (!text) {
- con_printk(KERN_ERR, con, "failed to allocate text buffer\n");
- printk_fallback_preferred_direct();
- goto out;
- }
-
- if (con->flags & CON_EXTENDED) {
- ext_text = kmalloc(CONSOLE_EXT_LOG_MAX, GFP_KERNEL);
- if (!ext_text) {
- con_printk(KERN_ERR, con, "failed to allocate ext_text buffer\n");
- printk_fallback_preferred_direct();
- goto out;
- }
- } else {
- dropped_text = kmalloc(DROPPED_TEXT_MAX, GFP_KERNEL);
- if (!dropped_text) {
- con_printk(KERN_ERR, con, "failed to allocate dropped_text buffer\n");
- printk_fallback_preferred_direct();
- goto out;
- }
- }
-
- con_printk(KERN_INFO, con, "printing thread started\n");
-
- for (;;) {
- /*
- * Guarantee this task is visible on the waitqueue before
- * checking the wake condition.
- *
- * The full memory barrier within set_current_state() of
- * prepare_to_wait_event() pairs with the full memory barrier
- * within wq_has_sleeper().
- *
- * This pairs with __wake_up_klogd:A.
- */
- error = wait_event_interruptible(log_wait,
- printer_should_wake(con, seq)); /* LMM(printk_kthread_func:A) */
-
- if (kthread_should_stop() || !printk_kthreads_available)
- break;
-
- if (error)
- continue;
-
- error = mutex_lock_interruptible(&con->lock);
- if (error)
- continue;
-
- if (con->blocked ||
- !console_kthread_printing_tryenter()) {
- /* Another context has locked the console_lock. */
- mutex_unlock(&con->lock);
- continue;
- }
-
- /*
- * Although this context has not locked the console_lock, it
- * is known that the console_lock is not locked and it is not
- * possible for any other context to lock the console_lock.
- * Therefore it is safe to read con->flags.
- */
-
- if (!__console_is_usable(con->flags)) {
- console_kthread_printing_exit();
- mutex_unlock(&con->lock);
- continue;
- }
-
- /*
- * Even though the printk kthread is always preemptible, it is
- * still not allowed to call cond_resched() from within
- * console drivers. The task may become non-preemptible in the
- * console driver call chain. For example, vt_console_print()
- * takes a spinlock and then can call into fbcon_redraw(),
- * which can conditionally invoke cond_resched().
- */
- console_may_schedule = 0;
- console_emit_next_record(con, text, ext_text, dropped_text);
-
- seq = con->seq;
-
- console_kthread_printing_exit();
-
- mutex_unlock(&con->lock);
- }
-
- con_printk(KERN_INFO, con, "printing thread stopped\n");
-out:
- kfree(dropped_text);
- kfree(ext_text);
- kfree(text);
-
- console_lock();
- /*
- * If this kthread is being stopped by another task, con->thread will
- * already be NULL. That is fine. The important thing is that it is
- * NULL after the kthread exits.
- */
- con->thread = NULL;
- console_unlock();
-
- return 0;
-}
-
-/* Must be called under console_lock. */
-static void printk_start_kthread(struct console *con)
-{
- /*
- * Do not start a kthread if there is no write() callback. The
- * kthreads assume the write() callback exists.
- */
- if (!con->write)
- return;
-
- con->thread = kthread_run(printk_kthread_func, con,
- "pr/%s%d", con->name, con->index);
- if (IS_ERR(con->thread)) {
- con->thread = NULL;
- con_printk(KERN_ERR, con, "unable to start printing thread\n");
- __printk_fallback_preferred_direct();
- return;
- }
-}
-
/*
* Delayed printk version, for scheduler-internal messages:
*/
-#define PRINTK_PENDING_WAKEUP 0x01
-#define PRINTK_PENDING_DIRECT_OUTPUT 0x02
+#define PRINTK_PENDING_WAKEUP 0x01
+#define PRINTK_PENDING_OUTPUT 0x02
static DEFINE_PER_CPU(int, printk_pending);
@@ -3899,14 +3447,10 @@ static void wake_up_klogd_work_func(struct irq_work *irq_work)
{
int pending = this_cpu_xchg(printk_pending, 0);
- if (pending & PRINTK_PENDING_DIRECT_OUTPUT) {
- printk_prefer_direct_enter();
-
+ if (pending & PRINTK_PENDING_OUTPUT) {
/* If trylock fails, someone else is doing the printing */
if (console_trylock())
console_unlock();
-
- printk_prefer_direct_exit();
}
if (pending & PRINTK_PENDING_WAKEUP)
@@ -3931,11 +3475,10 @@ static void __wake_up_klogd(int val)
* prepare_to_wait_event(), which is called after ___wait_event() adds
* the waiter but before it has checked the wait condition.
*
- * This pairs with devkmsg_read:A, syslog_print:A, and
- * printk_kthread_func:A.
+ * This pairs with devkmsg_read:A and syslog_print:A.
*/
if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */
- (val & PRINTK_PENDING_DIRECT_OUTPUT)) {
+ (val & PRINTK_PENDING_OUTPUT)) {
this_cpu_or(printk_pending, val);
irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
}
@@ -3953,17 +3496,7 @@ void defer_console_output(void)
* New messages may have been added directly to the ringbuffer
* using vprintk_store(), so wake any waiters as well.
*/
- int val = PRINTK_PENDING_WAKEUP;
-
- /*
- * Make sure that some context will print the messages when direct
- * printing is allowed. This happens in situations when the kthreads
- * may not be as reliable or perhaps unusable.
- */
- if (allow_direct_printing())
- val |= PRINTK_PENDING_DIRECT_OUTPUT;
-
- __wake_up_klogd(val);
+ __wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT);
}
void printk_trigger_flush(void)
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index caac4de1ea59..ef0f9a2044da 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -8,9 +8,7 @@
#include <linux/smp.h>
#include <linux/cpumask.h>
#include <linux/printk.h>
-#include <linux/console.h>
#include <linux/kprobes.h>
-#include <linux/delay.h>
#include "internal.h"
@@ -52,33 +50,3 @@ asmlinkage int vprintk(const char *fmt, va_list args)
return vprintk_default(fmt, args);
}
EXPORT_SYMBOL(vprintk);
-
-/**
- * try_block_console_kthreads() - Try to block console kthreads and
- * make the global console_lock() avaialble
- *
- * @timeout_ms: The maximum time (in ms) to wait.
- *
- * Prevent console kthreads from starting processing new messages. Wait
- * until the global console_lock() become available.
- *
- * Context: Can be called in any context.
- */
-void try_block_console_kthreads(int timeout_ms)
-{
- block_console_kthreads = true;
-
- /* Do not wait when the console lock could not be safely taken. */
- if (this_cpu_read(printk_context) || in_nmi())
- return;
-
- while (timeout_ms > 0) {
- if (console_trylock()) {
- console_unlock();
- return;
- }
-
- udelay(1000);
- timeout_ms -= 1;
- }
-}
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 4995c078cff9..a001e1e7a992 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -647,7 +647,6 @@ static void print_cpu_stall(unsigned long gps)
* See Documentation/RCU/stallwarn.rst for info on how to debug
* RCU CPU stall warnings.
*/
- printk_prefer_direct_enter();
trace_rcu_stall_warning(rcu_state.name, TPS("SelfDetected"));
pr_err("INFO: %s self-detected stall on CPU\n", rcu_state.name);
raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags);
@@ -685,7 +684,6 @@ static void print_cpu_stall(unsigned long gps)
*/
set_tsk_need_resched(current);
set_preempt_need_resched();
- printk_prefer_direct_exit();
}
static void check_cpu_stall(struct rcu_data *rdp)
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 80564ffafabf..3c35445bf5ad 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -82,7 +82,6 @@ void kernel_restart_prepare(char *cmd)
{
blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
system_state = SYSTEM_RESTART;
- try_block_console_kthreads(10000);
usermodehelper_disable();
device_shutdown();
}
@@ -271,7 +270,6 @@ static void kernel_shutdown_prepare(enum system_states state)
blocking_notifier_call_chain(&reboot_notifier_list,
(state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
system_state = state;
- try_block_console_kthreads(10000);
usermodehelper_disable();
device_shutdown();
}
@@ -821,11 +819,9 @@ static int __orderly_reboot(void)
ret = run_cmd(reboot_cmd);
if (ret) {
- printk_prefer_direct_enter();
pr_warn("Failed to start orderly reboot: forcing the issue\n");
emergency_sync();
kernel_restart(NULL);
- printk_prefer_direct_exit();
}
return ret;
@@ -838,7 +834,6 @@ static int __orderly_poweroff(bool force)
ret = run_cmd(poweroff_cmd);
if (ret && force) {
- printk_prefer_direct_enter();
pr_warn("Failed to start orderly shutdown: forcing the issue\n");
/*
@@ -848,7 +843,6 @@ static int __orderly_poweroff(bool force)
*/
emergency_sync();
kernel_power_off();
- printk_prefer_direct_exit();
}
return ret;
@@ -906,8 +900,6 @@ EXPORT_SYMBOL_GPL(orderly_reboot);
*/
static void hw_failure_emergency_poweroff_func(struct work_struct *work)
{
- printk_prefer_direct_enter();
-
/*
* We have reached here after the emergency shutdown waiting period has
* expired. This means orderly_poweroff has not been able to shut off
@@ -924,8 +916,6 @@ static void hw_failure_emergency_poweroff_func(struct work_struct *work)
*/
pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n");
emergency_restart();
-
- printk_prefer_direct_exit();
}
static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work,
@@ -964,13 +954,11 @@ void hw_protection_shutdown(const char *reason, int ms_until_forced)
{
static atomic_t allow_proceed = ATOMIC_INIT(1);
- printk_prefer_direct_enter();
-
pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason);
/* Shutdown should be initiated only once. */
if (!atomic_dec_and_test(&allow_proceed))
- goto out;
+ return;
/*
* Queue a backup emergency shutdown in the event of
@@ -978,8 +966,6 @@ void hw_protection_shutdown(const char *reason, int ms_until_forced)
*/
hw_failure_emergency_poweroff(ms_until_forced);
orderly_poweroff(true);
-out:
- printk_prefer_direct_exit();
}
EXPORT_SYMBOL_GPL(hw_protection_shutdown);
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 20a7a55e62b6..ecb0e8346e65 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -424,8 +424,6 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
/* Start period for the next softlockup warning. */
update_report_ts();
- printk_prefer_direct_enter();
-
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
@@ -444,8 +442,6 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
if (softlockup_panic)
panic("softlockup: hung tasks");
-
- printk_prefer_direct_exit();
}
return HRTIMER_RESTART;
diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 701f35f0e2d4..247bf0b1582c 100644
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -135,8 +135,6 @@ static void watchdog_overflow_callback(struct perf_event *event,
if (__this_cpu_read(hard_watchdog_warn) == true)
return;
- printk_prefer_direct_enter();
-
pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n",
this_cpu);
print_modules();
@@ -157,8 +155,6 @@ static void watchdog_overflow_callback(struct perf_event *event,
if (hardlockup_panic)
nmi_panic(regs, "Hard LOCKUP");
- printk_prefer_direct_exit();
-
__this_cpu_write(hard_watchdog_warn, true);
return;
}