linux-stable.git/kernel/kthread.c, branch linux-2.6.30.y

kthreads: fix kthread_create() vs kthread_stop() race

2009-09-09T03:33:58+00:00

The bug should be "accidently" fixed by recent changes in 2.6.31,
all kernels <= 2.6.30 need the fix. The problem was never noticed before,
it was found because it causes mysterious failures with GFS mount/umount.

Credits to Robert Peterson. He blaimed kthread.c from the very beginning.
But, despite my promise, I forgot to inspect the old implementation until
he did a lot of testing and reminded me. This led to huge delay in fixing
this bug.

kthread_stop() does put_task_struct(k) before it clears kthread_stop_info.k.
This means another kthread_create() can re-use this task_struct, but the
new kthread can still see kthread_should_stop() == T and exit even without
calling threadfn().

Reported-by: Robert Peterson 
Tested-by: Robert Peterson 
Signed-off-by: Oleg Nesterov 
Acked-by: Rusty Russell 
Signed-off-by: Greg Kroah-Hartman

kthread: move sched-realeted initialization from kthreadd context

2009-04-09T00:20:37+00:00

kthreadd is the single thread which implements ths "create" request, move
sched_setscheduler/etc from create_kthread() to kthread_create() to
improve the scalability.

We should be careful with sched_setscheduler(), use _nochek helper.

Signed-off-by: Oleg Nesterov 
Cc: Christoph Hellwig 
Cc: "Eric W. Biederman" 
Cc: Ingo Molnar 
Cc: Pavel Emelyanov 
Cc: Vitaliy Gusev 
Signed-off-by: Rusty Russell

kthread: Don't looking for a task in create_kthread() #2

2009-04-09T00:20:36+00:00

Remove the unnecessary find_task_by_pid_ns(). kthread() can just
use "current" to get the same result.

Signed-off-by: Vitaliy Gusev 
Acked-by: Oleg Nesterov 
Signed-off-by: Rusty Russell

cpumask: remove dangerous CPU_MASK_ALL_PTR, &CPU_MASK_ALL

2009-03-30T11:35:11+00:00

Impact: cleanup

(Thanks to Al Viro for reminding me of this, via Ingo)

CPU_MASK_ALL is the (deprecated) "all bits set" cpumask, defined as so:

	#define CPU_MASK_ALL (cpumask_t) { { ... } }

Taking the address of such a temporary is questionable at best,
unfortunately 321a8e9d (cpumask: add CPU_MASK_ALL_PTR macro) added
CPU_MASK_ALL_PTR:

	#define CPU_MASK_ALL_PTR (&CPU_MASK_ALL)

Which formalizes this practice.  One day gcc could bite us over this
usage (though we seem to have gotten away with it so far).

So replace everywhere which used &CPU_MASK_ALL or CPU_MASK_ALL_PTR
with the modern "cpu_all_mask" (a real const struct cpumask *).

Signed-off-by: Rusty Russell 
Acked-by: Ingo Molnar 
Reported-by: Al Viro 
Cc: Mike Travis

tracepoints: add DECLARE_TRACE() and DEFINE_TRACE()

2008-11-16T08:01:36+00:00

Impact: API *CHANGE*. Must update all tracepoint users.

Add DEFINE_TRACE() to tracepoints to let them declare the tracepoint
structure in a single spot for all the kernel. It helps reducing memory
consumption, especially when declaring a lot of tracepoints, e.g. for
kmalloc tracing.

*API CHANGE WARNING*: now, DECLARE_TRACE() must be used in headers for
tracepoint declarations rather than DEFINE_TRACE(). This is the sane way
to do it. The name previously used was misleading.

Updates scheduler instrumentation to follow this API change.

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Ingo Molnar

Merge branch 'tracing-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2008-10-20T20:35:07+00:00

* 'tracing-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (131 commits)
  tracing/fastboot: improve help text
  tracing/stacktrace: improve help text
  tracing/fastboot: fix initcalls disposition in bootgraph.pl
  tracing/fastboot: fix bootgraph.pl initcall name regexp
  tracing/fastboot: fix issues and improve output of bootgraph.pl
  tracepoints: synchronize unregister static inline
  tracepoints: tracepoint_synchronize_unregister()
  ftrace: make ftrace_test_p6nop disassembler-friendly
  markers: fix synchronize marker unregister static inline
  tracing/fastboot: add better resolution to initcall debug/tracing
  trace: add build-time check to avoid overrunning hex buffer
  ftrace: fix hex output mode of ftrace
  tracing/fastboot: fix initcalls disposition in bootgraph.pl
  tracing/fastboot: fix printk format typo in boot tracer
  ftrace: return an error when setting a nonexistent tracer
  ftrace: make some tracers reentrant
  ring-buffer: make reentrant
  ring-buffer: move page indexes into page headers
  tracing/fastboot: only trace non-module initcalls
  ftrace: move pc counter in irqtrace
  ...

Manually fix conflicts:
 - init/main.c: initcall tracing
 - kernel/module.c: verbose level vs tracepoints
 - scripts/bootgraph.pl: fallout from cherry-picking commits.

kthread_bind: use wait_task_inactive(TASK_UNINTERRUPTIBLE)

2008-10-20T15:52:39+00:00

Now that wait_task_inactive(task, state) checks task->state == state,
we can simplify the code and make this debugging check more robust.

Signed-off-by: Oleg Nesterov 
Cc: Roland McGrath 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tracing, sched: LTTng instrumentation - scheduler

2008-10-14T08:30:52+00:00

Instrument the scheduler activity (sched_switch, migration, wakeups,
wait for a task, signal delivery) and process/thread
creation/destruction (fork, exit, kthread stop). Actually, kthread
creation is not instrumented in this patch because it is architecture
dependent. It allows to connect tracers such as ftrace which detects
scheduling latencies, good/bad scheduler decisions. Tools like LTTng can
export this scheduler information along with instrumentation of the rest
of the kernel activity to perform post-mortem analysis on the scheduler
activity.

About the performance impact of tracepoints (which is comparable to
markers), even without immediate values optimizations, tests done by
Hideo Aoki on ia64 show no regression. His test case was using hackbench
on a kernel where scheduler instrumentation (about 5 events in code
scheduler code) was added. See the "Tracepoints" patch header for
performance result detail.

Changelog :

- Change instrumentation location and parameter to match ftrace
  instrumentation, previously done with kernel markers.

[ mingo@elte.hu: conflict resolutions ]
Signed-off-by: Mathieu Desnoyers 
Acked-by: 'Peter Zijlstra' 
Signed-off-by: Ingo Molnar

tracehook: wait_task_inactive

2008-07-26T19:00:09+00:00

This extends wait_task_inactive() with a new argument so it can be used in
a "soft" mode where it will check for the task changing state unexpectedly
and back off.  There is no change to existing callers.  This lays the
groundwork to allow robust, noninvasive tracing that can try to sample a
blocked thread but back off safely if it wakes up.

Signed-off-by: Roland McGrath 
Cc: Oleg Nesterov 
Reviewed-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kthread: reduce stack pressure in create_kthread and kthreadd

2008-07-18T16:46:58+00:00

  * Replace:

  	set_cpus_allowed(..., CPU_MASK_ALL)

    with:

  	set_cpus_allowed_ptr(..., CPU_MASK_ALL_PTR)

    to remove excessive stack requirements when NR_CPUS=4096.

Signed-off-by: Mike Travis 
Cc: Andrew Morton 
Signed-off-by: Ingo Molnar