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If a process issues an URB from userspace and (starts to) terminate
before the URB comes back, we run into the issue described above. This
is because the urb saves a pointer to "current" when it is posted to the
device, but there's no guarantee that this pointer is still valid
afterwards.
In fact, there are three separate issues:
1) the pointer to "current" can become invalid, since the task could be
completely gone when the URB completion comes back from the device.
2) Even if the saved task pointer is still pointing to a valid task_struct,
task_struct->sighand could have gone meanwhile.
3) Even if the process is perfectly fine, permissions may have changed,
and we can no longer send it a signal.
So what we do instead, is to save the PID and uid's of the process, and
introduce a new kill_proc_info_as_uid() function.
Signed-off-by: Harald Welte <laforge@gnumonks.org>
[ Fixed up types and added symbol exports ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The following patch makes swsusp avoid the possible temporary corruption
of page translation tables during resume on x86-64. This is achieved by
creating a copy of the relevant page tables that will not be modified by
swsusp and can be safely used by it on resume.
The problem is that during resume on x86-64 swsusp may temporarily
corrupt the page tables used for the direct mapping of RAM. If that
happens, a page fault occurs and cannot be handled properly, which leads
to the solid hang of the affected system. This leads to the loss of the
system's state from before suspend and may result in the loss of data or
the corruption of filesystems, so it is a serious issue. Also, it
appears to happen quite often (for me, as often as 50% of the time).
The problem is related to the fact that (at least) one of the PMD
entries used in the direct memory mapping (starting at PAGE_OFFSET)
points to a page table the physical address of which is much greater
than the physical address of the PMD entry itself. Moreover,
unfortunately, the physical address of the page table before suspend
(i.e. the one stored in the suspend image) happens to be different to
the physical address of the corresponding page table used during resume
(i.e. the one that is valid right before swsusp_arch_resume() in
arch/x86_64/kernel/suspend_asm.S is executed). Thus while the image is
restored, the "offending" PMD entry gets overwritten, so it does not
point to the right physical address any more (i.e. there's no page
table at the address pointed to by it, because it points to the address
the page table has been at during suspend). Consequently, if the PMD
entry is used later on, and it _is_ used in the process of copying the
image pages, a page fault occurs, but it cannot be handled in the normal
way and the system hangs.
In principle we can call create_resume_mapping() from
swsusp_arch_resume() (ie. from suspend_asm.S), but then the memory
allocations in create_resume_mapping(), resume_pud_mapping(), and
resume_pmd_mapping() must be made carefully so that we use _only_
NosaveFree pages in them (the other pages are overwritten by the loop in
swsusp_arch_resume()). Additionally, we are in atomic context at that
time, so we cannot use GFP_KERNEL. Moreover, if one of the allocations
fails, we should free all of the allocated pages, so we need to trace
them somehow.
All of this is done in the appended patch, except that the functions
populating the page tables are located in arch/x86_64/kernel/suspend.c
rather than in init.c. It may be done in a more elegan way in the
future, with the help of some swsusp patches that are in the works now.
[AK: move some externs into headers, renamed a function]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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- added typedef unsigned int __nocast gfp_t;
- replaced __nocast uses for gfp flags with gfp_t - it gives exactly
the same warnings as far as sparse is concerned, doesn't change
generated code (from gcc point of view we replaced unsigned int with
typedef) and documents what's going on far better.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Let's suppose we have 2 threads in thread group:
A - does coredump
B - has pending SIGSTOP
thread A thread B
do_coredump: get_signal_to_deliver:
lock(->sighand)
->signal->flags = SIGNAL_GROUP_EXIT
unlock(->sighand)
lock(->sighand)
signr = dequeue_signal()
->signal->flags |= SIGNAL_STOP_DEQUEUED
return SIGSTOP;
do_signal_stop:
unlock(->sighand)
coredump_wait:
zap_threads:
lock(tasklist_lock)
send SIGKILL to B
// signal_wake_up() does nothing
unlock(tasklist_lock)
lock(tasklist_lock)
lock(->sighand)
re-check sig->flags & SIGNAL_STOP_DEQUEUED, yes
set_current_state(TASK_STOPPED);
finish_stop:
schedule();
// ->state == TASK_STOPPED
wait_for_completion(&startup_done)
// waits for complete() from B,
// ->state == TASK_UNINTERRUPTIBLE
We can't wake up 'B' in any way:
SIGCONT will be ignored because handle_stop_signal() sees
->signal->flags & SIGNAL_GROUP_EXIT.
sys_kill(SIGKILL)->__group_complete_signal() will choose
uninterruptible 'A', so it can't help.
sys_tkill(B, SIGKILL) will be ignored by specific_send_sig_info()
because B already has pending SIGKILL.
This scenario is not possbile if 'A' does do_group_exit(), because
it sets sig->flags = SIGNAL_GROUP_EXIT and delivers SIGKILL to
subthreads atomically, holding both tasklist_lock and sighand->lock.
That means that do_signal_stop() will notice !SIGNAL_STOP_DEQUEUED
after re-locking ->sighand. And it is not possible to any other
thread to re-add SIGNAL_STOP_DEQUEUED later, because dequeue_signal()
can only return SIGKILL.
I think it is better to change do_coredump() to do sigaddset(SIGKILL)
and signal_wake_up() under sighand->lock, but this patch is much
simpler.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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We should always use bitmask ops, rather than depend on some ordering of
the different states. With the TASK_NONINTERACTIVE flag, the inequality
doesn't really work.
Oleg Nesterov argues (likely correctly) that this test is unnecessary in
the first place. However, the minimal fix for now is to at least make
it work in the presense of TASK_NONINTERACTIVE. Waiting for consensus
from Roland & co on potential bigger cleanups.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Switched cpuset_common_file_read() to simple_read_from_buffer(), killed
a bunch of useless (and not quite correct - e.g. min(size_t,ssize_t))
code.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Any tests using < TASK_STOPPED or the like are left over from the time
when the TASK_ZOMBIE and TASK_DEAD bits were in the same word, and it
served to check for "stopped or dead". I think this one in
do_signal_stop is the only such case. It has been buggy ever since
exit_state was separated, and isn't testing the exit_state value.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Don't leak a page of memory if user reads a cpuset file past eof.
Signed-off-by: KUROSAWA Takahiro <kurosawa@valinux.co.jp>
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The following patch makes swsusp avoid problems during resume if there are
too many pages to save on suspend. It adds a constant that allows us to
verify if we are going to save too many pages and implements the check
(this is done as early as we can tell that the check will trigger, which is
in swsusp_alloc()).
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Dave Jones says:
... if the modprobe.conf has trailing whitespace, modules fail to load
with the following helpful message..
snd_intel8x0: Unknown parameter `'
Previous version truncated last argument.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Prevent swsusp from leaking some memory in case of an error in
read_pagedir(). It also prevents the BUG_ON() from triggering if there's
an error while reading swap.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The following patch removes some wrong code from the data_free() function
in swsusp.
This function could only be called if there's an error while writing the
suspend image to swap, so it is not triggered easily. However, if
triggered, it would probably corrupt some memory.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Bhavesh P. Davda <bhavesh@avaya.com> noticed that SIGKILL wouldn't
properly kill a process under just the right cicumstances: a stopped
task that already had another signal queued would get the SIGKILL
queued onto the shared queue, and there it would remain until SIGCONT.
This simplifies the signal acceptance logic, and fixes the bug in the
process.
Losely based on an earlier patch by Bhavesh.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix comments in swsusp.
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The following patch makes swsusp avoid triggering the BUG_ON() in
swsusp_suspend() if there is not enough memory for suspend.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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In the lead up to 2.6.13 I fixed a large number of reboot problems by
making the calling conventions consistent. Despite checking and double
checking my work it appears I missed an obvious one.
The S4 suspend code for PM_DISK_PLATFORM was also calling device_shutdown
without setting system_state, and was not calling the appropriate
reboot_notifier.
This patch fixes the bug by replacing the call of device_suspend with
kernel_poweroff_prepare.
Various forms of this failure have been fixed and tracked for a while.
Thanks for tracking this down go to: Alexey Starikovskiy, Meelis Roos
<mroos@linux.ee>, Nigel Cunningham <ncunningham@cyclades.com>, Pierre
Ossman <drzeus-list@drzeus.cx>
History of this bug is at:
http://bugme.osdl.org/show_bug.cgi?id=4320
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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In the lead up to 2.6.13 I fixed a large number of reboot problems by
making the calling conventions consistent. Despite checking and double
checking my work it appears I missed an obvious one.
This first patch simply refactors the reboot routines so all of the
preparation for various kinds of reboots are in their own functions.
Making it very hard to get the various kinds of reboot out of sync.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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ia64's sched_clock() accesses per-cpu data which isn't set up at boot time.
Hence ia64 cannot use printk timestamping, because printk() will crash in
sched_clock().
So make printk() use printk_clock(), defaulting to sched_clock(), overrideable
by the architecture via attribute(weak).
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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With the new fdtable locking rules, you have to protect fdtable with either
->file_lock or rcu_read_lock/unlock(). There are some places where we
aren't doing either. This patch fixes those places.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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2.6.13 incorporated Alan Cox's patch for /proc/sys/fs/suid_dumpable (one
version of this patch can be found here
http://marc.theaimsgroup.com/?l=linux-kernel&m=109647550421014&w=2 ).
This patch also made corresponding changes in kernel/sys.c to change the
prctl() PR_SET_DUMPABLE operation so that the permitted range of 'arg2' was
modified from 0..1 to 0..2.
However, a corresponding change was not made for PR_GET_DUMPABLE: if the
dumpable flag is non-zero, then PR_GET_DUMPABLE always returns 1, so that
the caller can't determine the true setting of this flag.
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix a problem wherein a new-born task is added to a dead CPU.
Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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fix up the runqueue lock owner only if we truly did a context-switch
with the runqueue lock held. Impacts ia64, mips, sparc64 and arm.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Use the add_taint() interface for setting tainted bit flags instead of
doing it manually.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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These functions don't need schedule_timeout()'s barrier.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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- Remove unused irqrsp field
- Remove pda->me
- Optimize set_softirq_pending slightly
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Optimize the deadlock avoidance check on the global cpuset
semaphore cpuset_sem. Instead of adding a depth counter to the
task struct of each task, rather just two words are enough, one
to store the depth and the other the current cpuset_sem holder.
Thanks to Nikita Danilov for the idea.
Signed-off-by: Paul Jackson <pj@sgi.com>
[ We may want to change this further, but at least it's now
a totally internal decision to the cpusets code ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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..and only enable them for ia64. The functions are only valid
when the whole system has been totally stopped and no scheduler
activity is ongoing on any CPU, and interrupts are globally
disabled.
In other words, they aren't useful for anything else. So make
sure that nobody can use them by mistake.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Scheduler hooks to see/change which process is deemed to be on a cpu.
Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Use schedule_timeout_{,un}interruptible() instead of
set_current_state()/schedule_timeout() to reduce kernel size.
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Add schedule_timeout_{,un}interruptible() interfaces so that
schedule_timeout() callers don't have to worry about forgetting to add the
set_current_state() call beforehand.
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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for kernel/acct.c:
- fix typos
- add kerneldoc for non-static functions
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Don't pull tasks from a group if that would cause the group's total load to
drop below its total cpu_power (ie. cause the group to start going idle).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Jack Steiner brought this issue at my OLS talk.
Take a scenario where two tasks are pinned to two HT threads in a physical
package. Idle packages in the system will keep kicking migration_thread on
the busy package with out any success.
We will run into similar scenarios in the presence of CMP/NUMA.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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In sys_sched_yield(), we cache current->array in the "array" variable, thus
there's no need to dereference "current" again later.
Signed-Off-By: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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If an idle sibling of an HT queue encounters a busy sibling, then make
higher level load balancing of the non-idle variety.
Performance of multiprocessor HT systems with low numbers of tasks
(generally < number of virtual CPUs) can be significantly worse than the
exact same workloads when running in non-HT mode. The reason is largely
due to poor scheduling behaviour.
This patch improves the situation, making the performance gap far less
significant on one problematic test case (tbench).
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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During periodic load balancing, don't hold this runqueue's lock while
scanning remote runqueues, which can take a non trivial amount of time
especially on very large systems.
Holding the runqueue lock will only help to stabilise ->nr_running, however
this doesn't do much to help because tasks being woken will simply get held
up on the runqueue lock, so ->nr_running would not provide a really
accurate picture of runqueue load in that case anyway.
What's more, ->nr_running (and possibly the cpu_load averages) of remote
runqueues won't be stable anyway, so load balancing is always an inexact
operation.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Similarly to the earlier change in load_balance, only lock the runqueue in
load_balance_newidle if the busiest queue found has a nr_running > 1. This
will reduce frequency of expensive remote runqueue lock aquisitions in the
schedule() path on some workloads.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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William Weston reported unusually high scheduling latencies on his x86 HT
box, on the -RT kernel. I managed to reproduce it on my HT box and the
latency tracer shows the incident in action:
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
du-2803 3Dnh2 0us : __trace_start_sched_wakeup (try_to_wake_up)
..............................................................
... we are running on CPU#3, PID 2778 gets woken to CPU#1: ...
..............................................................
du-2803 3Dnh2 0us : __trace_start_sched_wakeup <<...>-2778> (73 1)
du-2803 3Dnh2 0us : _raw_spin_unlock (try_to_wake_up)
................................................
... still on CPU#3, we send an IPI to CPU#1: ...
................................................
du-2803 3Dnh1 0us : resched_task (try_to_wake_up)
du-2803 3Dnh1 1us : smp_send_reschedule (try_to_wake_up)
du-2803 3Dnh1 1us : send_IPI_mask_bitmask (smp_send_reschedule)
du-2803 3Dnh1 2us : _raw_spin_unlock_irqrestore (try_to_wake_up)
...............................................
... 1 usec later, the IPI arrives on CPU#1: ...
...............................................
<idle>-0 1Dnh. 2us : smp_reschedule_interrupt (c0100c5a 0 0)
So far so good, this is the normal wakeup/preemption mechanism. But here
comes the scheduler anomaly on CPU#1:
<idle>-0 1Dnh. 2us : preempt_schedule_irq (need_resched)
<idle>-0 1Dnh. 2us : preempt_schedule_irq (need_resched)
<idle>-0 1Dnh. 3us : __schedule (preempt_schedule_irq)
<idle>-0 1Dnh. 3us : profile_hit (__schedule)
<idle>-0 1Dnh1 3us : sched_clock (__schedule)
<idle>-0 1Dnh1 4us : _raw_spin_lock_irq (__schedule)
<idle>-0 1Dnh1 4us : _raw_spin_lock_irqsave (__schedule)
<idle>-0 1Dnh2 5us : _raw_spin_unlock (__schedule)
<idle>-0 1Dnh1 5us : preempt_schedule (__schedule)
<idle>-0 1Dnh1 6us : _raw_spin_lock (__schedule)
<idle>-0 1Dnh2 6us : find_next_bit (__schedule)
<idle>-0 1Dnh2 6us : _raw_spin_lock (__schedule)
<idle>-0 1Dnh3 7us : find_next_bit (__schedule)
<idle>-0 1Dnh3 7us : find_next_bit (__schedule)
<idle>-0 1Dnh3 8us : _raw_spin_unlock (__schedule)
<idle>-0 1Dnh2 8us : preempt_schedule (__schedule)
<idle>-0 1Dnh2 8us : find_next_bit (__schedule)
<idle>-0 1Dnh2 9us : trace_stop_sched_switched (__schedule)
<idle>-0 1Dnh2 9us : _raw_spin_lock (trace_stop_sched_switched)
<idle>-0 1Dnh3 10us : trace_stop_sched_switched <<...>-2778> (73 8c)
<idle>-0 1Dnh3 10us : _raw_spin_unlock (trace_stop_sched_switched)
<idle>-0 1Dnh1 10us : _raw_spin_unlock (__schedule)
<idle>-0 1Dnh. 11us : local_irq_enable_noresched (preempt_schedule_irq)
<idle>-0 1Dnh. 11us < (0)
we didnt pick up pid 2778! It only gets scheduled much later:
<...>-2778 1Dnh2 412us : __switch_to (__schedule)
<...>-2778 1Dnh2 413us : __schedule <<idle>-0> (8c 73)
<...>-2778 1Dnh2 413us : _raw_spin_unlock (__schedule)
<...>-2778 1Dnh1 413us : trace_stop_sched_switched (__schedule)
<...>-2778 1Dnh1 414us : _raw_spin_lock (trace_stop_sched_switched)
<...>-2778 1Dnh2 414us : trace_stop_sched_switched <<...>-2778> (73 1)
<...>-2778 1Dnh2 414us : _raw_spin_unlock (trace_stop_sched_switched)
<...>-2778 1Dnh1 415us : trace_stop_sched_switched (__schedule)
the reason for this anomaly is the following code in dependent_sleeper():
/*
* If a user task with lower static priority than the
* running task on the SMT sibling is trying to schedule,
* delay it till there is proportionately less timeslice
* left of the sibling task to prevent a lower priority
* task from using an unfair proportion of the
* physical cpu's resources. -ck
*/
[...]
if (((smt_curr->time_slice * (100 - sd->per_cpu_gain) /
100) > task_timeslice(p)))
ret = 1;
Note that in contrast to the comment above, we dont actually do the check
based on static priority, we do the check based on timeslices. But
timeslices go up and down, and even highprio tasks can randomly have very
low timeslices (just before their next refill) and can thus be judged as
'lowprio' by the above piece of code. This condition is clearly buggy.
The correct test is to check for static_prio _and_ to check for the
preemption priority. Even on different static priority levels, a
higher-prio interactive task should not be delayed due to a
higher-static-prio CPU hog.
There is a symmetric bug in the 'kick SMT sibling' code of this function as
well, which can be solved in a similar way.
The patch below (against the current scheduler queue in -mm) fixes both
bugs. I have build and boot-tested this on x86 SMT, and nice +20 tasks
still get properly throttled - so the dependent-sleeper logic is still in
action.
btw., these bugs pessimised the SMT scheduler because the 'delay wakeup'
property was applied too liberally, so this fix is likely a throughput
improvement as well.
I separated out a smt_slice() function to make the code easier to read.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch implements a task state bit (TASK_NONINTERACTIVE), which can be
used by blocking points to mark the task's wait as "non-interactive". This
does not mean the task will be considered a CPU-hog - the wait will simply
not have an effect on the waiting task's priority - positive or negative
alike. Right now only pipe_wait() will make use of it, because it's a
common source of not-so-interactive waits (kernel compilation jobs, etc.).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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whitespace cleanups.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Add relevant checks into find_idlest_group() and find_idlest_cpu() to make
them return only the groups that have allowed CPUs and allowed CPUs
respectively.
Signed-off-by: M.Baris Demiray <baris@labristeknoloji.com>
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The hyperthread aware nice handling currently puts to sleep any non real
time task when a real time task is running on its sibling cpu. This can
lead to prolonged starvation by having the non real time task pegged to the
cpu with load balancing not pulling that task away.
Currently we force lower priority hyperthread tasks to run a percentage of
time difference based on timeslice differences which is meaningless when
comparing real time tasks to SCHED_NORMAL tasks. We can allow non real
time tasks to run with real time tasks on the sibling up to per_cpu_gain%
if we use jiffies as a counter.
Cleanups and micro-optimisations to the relevant code section should make
it more understandable as well.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The cpusets-formalize-intermediate-gfp_kernel-containment patch
has a deadlock problem.
This patch was part of a set of four patches to make more
extensive use of the cpuset 'mem_exclusive' attribute to
manage kernel GFP_KERNEL memory allocations and to constrain
the out-of-memory (oom) killer.
A task that is changing cpusets in particular ways on a system
when it is very short of free memory could double trip over
the global cpuset_sem semaphore (get the lock and then deadlock
trying to get it again).
The second attempt to get cpuset_sem would be in the routine
cpuset_zone_allowed(). This was discovered by code inspection.
I can not reproduce the problem except with an artifically
hacked kernel and a specialized stress test.
In real life you cannot hit this unless you are manipulating
cpusets, and are very unlikely to hit it unless you are rapidly
modifying cpusets on a memory tight system. Even then it would
be a rare occurence.
If you did hit it, the task double tripping over cpuset_sem
would deadlock in the kernel, and any other task also trying
to manipulate cpusets would deadlock there too, on cpuset_sem.
Your batch manager would be wedged solid (if it was cpuset
savvy), but classic Unix shells and utilities would work well
enough to reboot the system.
The unusual condition that led to this bug is that unlike most
semaphores, cpuset_sem _can_ be acquired while in the page
allocation code, when __alloc_pages() calls cpuset_zone_allowed.
So it easy to mistakenly perform the following sequence:
1) task makes system call to alter a cpuset
2) take cpuset_sem
3) try to allocate memory
4) memory allocator, via cpuset_zone_allowed, trys to take cpuset_sem
5) deadlock
The reason that this is not a serious bug for most users
is that almost all calls to allocate memory don't require
taking cpuset_sem. Only some code paths off the beaten
track require taking cpuset_sem -- which is good. Taking
a global semaphore on the main code path for allocating
memory would not scale well.
This patch fixes this deadlock by wrapping the up() and down()
calls on cpuset_sem in kernel/cpuset.c with code that tracks
the nesting depth of the current task on that semaphore, and
only does the real down() if the task doesn't hold the lock
already, and only does the real up() if the nesting depth
(number of unmatched downs) is exactly one.
The previous required use of refresh_mems(), anytime that
the cpuset_sem semaphore was acquired and the code executed
while holding that semaphore might try to allocate memory, is
no longer required. Two refresh_mems() calls were removed
thanks to this. This is a good change, as failing to get
all the necessary refresh_mems() calls placed was a primary
source of bugs in this cpuset code. The only remaining call
to refresh_mems() is made while doing a memory allocation,
if certain task memory placement data needs to be updated
from its cpuset, due to the cpuset having been changed behind
the tasks back.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch (written by me and also containing many suggestions of Arjan van
de Ven) does a major cleanup of the spinlock code. It does the following
things:
- consolidates and enhances the spinlock/rwlock debugging code
- simplifies the asm/spinlock.h files
- encapsulates the raw spinlock type and moves generic spinlock
features (such as ->break_lock) into the generic code.
- cleans up the spinlock code hierarchy to get rid of the spaghetti.
Most notably there's now only a single variant of the debugging code,
located in lib/spinlock_debug.c. (previously we had one SMP debugging
variant per architecture, plus a separate generic one for UP builds)
Also, i've enhanced the rwlock debugging facility, it will now track
write-owners. There is new spinlock-owner/CPU-tracking on SMP builds too.
All locks have lockup detection now, which will work for both soft and hard
spin/rwlock lockups.
The arch-level include files now only contain the minimally necessary
subset of the spinlock code - all the rest that can be generalized now
lives in the generic headers:
include/asm-i386/spinlock_types.h | 16
include/asm-x86_64/spinlock_types.h | 16
I have also split up the various spinlock variants into separate files,
making it easier to see which does what. The new layout is:
SMP | UP
----------------------------|-----------------------------------
asm/spinlock_types_smp.h | linux/spinlock_types_up.h
linux/spinlock_types.h | linux/spinlock_types.h
asm/spinlock_smp.h | linux/spinlock_up.h
linux/spinlock_api_smp.h | linux/spinlock_api_up.h
linux/spinlock.h | linux/spinlock.h
/*
* here's the role of the various spinlock/rwlock related include files:
*
* on SMP builds:
*
* asm/spinlock_types.h: contains the raw_spinlock_t/raw_rwlock_t and the
* initializers
*
* linux/spinlock_types.h:
* defines the generic type and initializers
*
* asm/spinlock.h: contains the __raw_spin_*()/etc. lowlevel
* implementations, mostly inline assembly code
*
* (also included on UP-debug builds:)
*
* linux/spinlock_api_smp.h:
* contains the prototypes for the _spin_*() APIs.
*
* linux/spinlock.h: builds the final spin_*() APIs.
*
* on UP builds:
*
* linux/spinlock_type_up.h:
* contains the generic, simplified UP spinlock type.
* (which is an empty structure on non-debug builds)
*
* linux/spinlock_types.h:
* defines the generic type and initializers
*
* linux/spinlock_up.h:
* contains the __raw_spin_*()/etc. version of UP
* builds. (which are NOPs on non-debug, non-preempt
* builds)
*
* (included on UP-non-debug builds:)
*
* linux/spinlock_api_up.h:
* builds the _spin_*() APIs.
*
* linux/spinlock.h: builds the final spin_*() APIs.
*/
All SMP and UP architectures are converted by this patch.
arm, i386, ia64, ppc, ppc64, s390/s390x, x64 was build-tested via
crosscompilers. m32r, mips, sh, sparc, have not been tested yet, but should
be mostly fine.
From: Grant Grundler <grundler@parisc-linux.org>
Booted and lightly tested on a500-44 (64-bit, SMP kernel, dual CPU).
Builds 32-bit SMP kernel (not booted or tested). I did not try to build
non-SMP kernels. That should be trivial to fix up later if necessary.
I converted bit ops atomic_hash lock to raw_spinlock_t. Doing so avoids
some ugly nesting of linux/*.h and asm/*.h files. Those particular locks
are well tested and contained entirely inside arch specific code. I do NOT
expect any new issues to arise with them.
If someone does ever need to use debug/metrics with them, then they will
need to unravel this hairball between spinlocks, atomic ops, and bit ops
that exist only because parisc has exactly one atomic instruction: LDCW
(load and clear word).
From: "Luck, Tony" <tony.luck@intel.com>
ia64 fix
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjanv@infradead.org>
Signed-off-by: Grant Grundler <grundler@parisc-linux.org>
Cc: Matthew Wilcox <willy@debian.org>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>
Signed-off-by: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Patch to eliminate struct files_struct.file_lock spinlock on the reader side
and use rcu refcounting rcuref_xxx api for the f_count refcounter. The
updates to the fdtable are done by allocating a new fdtable structure and
setting files->fdt to point to the new structure. The fdtable structure is
protected by RCU thereby allowing lock-free lookup. For fd arrays/sets that
are vmalloced, we use keventd to free them since RCU callbacks can't sleep. A
global list of fdtable to be freed is not scalable, so we use a per-cpu list.
If keventd is already handling the current cpu's work, we use a timer to defer
queueing of that work.
Since the last publication, this patch has been re-written to avoid using
explicit memory barriers and use rcu_assign_pointer(), rcu_dereference()
premitives instead. This required that the fd information is kept in a
separate structure (fdtable) and updated atomically.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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In order for the RCU to work, the file table array, sets and their sizes must
be updated atomically. Instead of ensuring this through too many memory
barriers, we put the arrays and their sizes in a separate structure. This
patch takes the first step of putting the file table elements in a separate
structure fdtable that is embedded withing files_struct. It also changes all
the users to refer to the file table using files_fdtable() macro. Subsequent
applciation of RCU becomes easier after this.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Adds a set of primitives to do reference counting for objects that are looked
up without locks using RCU.
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch fixes minor problem that the CPUSETS have when files in the
cpuset filesystem are read after lseek()-ed beyond the EOF.
Signed-off-by: KUROSAWA Takahiro <kurosawa@valinux.co.jp>
Acked-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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