linux-toradex.git/kernel/kthread.c, branch v4.11-rc1

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:35+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  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 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:27+00:00

We are going to move scheduler ABI details to ,
which will be used from a number of .c files.

Create empty placeholder header that maps to .

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

time: Remove CONFIG_TIMER_STATS

2017-02-10T10:15:08+00:00

Currently CONFIG_TIMER_STATS exposes process information across namespaces:

kernel/time/timer_list.c print_timer():

        SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);

/proc/timer_list:

 #11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570

Given that the tracer can give the same information, this patch entirely
removes CONFIG_TIMER_STATS.

Suggested-by: Thomas Gleixner 
Signed-off-by: Kees Cook 
Acked-by: John Stultz 
Cc: Nicolas Pitre 
Cc: linux-doc@vger.kernel.org
Cc: Lai Jiangshan 
Cc: Shuah Khan 
Cc: Xing Gao 
Cc: Jonathan Corbet 
Cc: Jessica Frazelle 
Cc: kernel-hardening@lists.openwall.com
Cc: Nicolas Iooss 
Cc: "Paul E. McKenney" 
Cc: Petr Mladek 
Cc: Richard Cochran 
Cc: Tejun Heo 
Cc: Michal Marek 
Cc: Josh Poimboeuf 
Cc: Dmitry Vyukov 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Cc: Olof Johansson 
Cc: Andrew Morton 
Cc: linux-api@vger.kernel.org
Cc: Arjan van de Ven 
Link: http://lkml.kernel.org/r/20170208192659.GA32582@beast
Signed-off-by: Thomas Gleixner

kthread: add __printf attributes

2016-12-13T02:55:06+00:00

When commit fbae2d44aa1d ("kthread: add kthread_create_worker*()")
introduced some kthread_create_...() functions which were taking
printf-like parametter, it introduced __printf attributes to some
functions (e.g.  kthread_create_worker()).  Nevertheless some new
functions were forgotten (they have been detected thanks to
-Wmissing-format-attribute warning flag).

Add the missing __printf attributes to the newly-introduced functions in
order to detect formatting issues at build-time with -Wformat flag.

Link: http://lkml.kernel.org/r/20161126193543.22672-1-nicolas.iooss_linux@m4x.org
Signed-off-by: Nicolas Iooss 
Reviewed-by: Petr Mladek 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kthread: Don't abuse kthread_create_on_cpu() in __kthread_create_worker()

2016-12-08T13:36:20+00:00

kthread_create_on_cpu() sets KTHREAD_IS_PER_CPU and kthread->cpu, this
only makes sense if this kthread can be parked/unparked by cpuhp code.
kthread workers never call kthread_parkme() so this has no effect.

Change __kthread_create_worker() to simply call kthread_bind(task, cpu).
The very fact that kthread_create_on_cpu() doesn't accept a generic fmt
shows that it should not be used outside of smpboot.c.

Now, the only reason we can not unexport this helper and move it into
smpboot.c is that it sets kthread->cpu and struct kthread is not exported.
And the only reason we can not kill kthread->cpu is that kthread_unpark()
is used by drivers/gpu/drm/amd/scheduler/gpu_scheduler.c and thus we can
not turn _unpark into kthread_unpark(struct smp_hotplug_thread *, cpu).

Signed-off-by: Oleg Nesterov 
Tested-by: Petr Mladek 
Acked-by: Peter Zijlstra (Intel) 
Reviewed-by: Petr Mladek 
Cc: Chunming Zhou 
Cc: Roman Pen 
Cc: Andy Lutomirski 
Cc: Tejun Heo 
Cc: Andy Lutomirski 
Cc: Alex Deucher 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/20161129175110.GA5342@redhat.com
Signed-off-by: Thomas Gleixner

kthread: Don't use to_live_kthread() in kthread_[un]park()

2016-12-08T13:36:19+00:00

Now that to_kthread() is always validm change kthread_park() and
kthread_unpark() to use it and kill to_live_kthread().

The conversion of kthread_unpark() is trivial. If KTHREAD_IS_PARKED is set
then the task has called complete(&self->parked) and there the function
cannot race against a concurrent kthread_stop() and exit.

kthread_park() is more tricky, because its semantics are not well
defined. It returns -ENOSYS if the thread exited but this can never happen
and as Roman pointed out kthread_park() can obviously block forever if it
would race with the exiting kthread.

The usage of kthread_park() in cpuhp code (cpu.c, smpboot.c, stop_machine.c)
is fine. It can never see an exiting/exited kthread, smpboot_destroy_threads()
clears *ht->store, smpboot_park_thread() checks it is not NULL under the same
smpboot_threads_lock. cpuhp_threads and cpu_stop_threads never exit, so other
callers are fine too.

But it has two more users:

- watchdog_park_threads():

  The code is actually correct, get_online_cpus() ensures that
  kthread_park() can't race with itself (note that kthread_park() can't
  handle this race correctly), but it should not use kthread_park()
  directly.

- drivers/gpu/drm/amd/scheduler/gpu_scheduler.c should not use
  kthread_park() either.

  kthread_park() must not be called after amd_sched_fini() which does
  kthread_stop(), otherwise even to_live_kthread() is not safe because
  task_struct can be already freed and sched->thread can point to nowhere.

The usage of kthread_park/unpark should either be restricted to core code
which is properly protected against the exit race or made more robust so it
is safe to use it in drivers.

To catch eventual exit issues, add a WARN_ON(PF_EXITING) for now.

Signed-off-by: Oleg Nesterov 
Acked-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Cc: Chunming Zhou 
Cc: Roman Pen 
Cc: Petr Mladek 
Cc: Andy Lutomirski 
Cc: Tejun Heo 
Cc: Andy Lutomirski 
Cc: Alex Deucher 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/20161129175107.GA5339@redhat.com
Signed-off-by: Thomas Gleixner

kthread: Don't use to_live_kthread() in kthread_stop()

2016-12-08T13:36:19+00:00

kthread_stop() had to use to_live_kthread() simply because it was not
possible to access kthread->exited after the exiting task clears
task_struct->vfork_done. Now that to_kthread() is always valid,
wake_up_process() + wait_for_completion() can be done
ununconditionally. It's not an issue anymore if the task has already issued
complete_vfork_done() or died.

The exiting task can get the spurious wakeup after mm_release() but this is
possible without this change too and is fine; do_task_dead() ensures that
this can't make any harm.

As a further enhancement this could be converted to task_work_add() later,
so ->vfork_done can be avoided completely.

Signed-off-by: Oleg Nesterov 
Acked-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Cc: Chunming Zhou 
Cc: Roman Pen 
Cc: Petr Mladek 
Cc: Andy Lutomirski 
Cc: Tejun Heo 
Cc: Andy Lutomirski 
Cc: Alex Deucher 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/20161129175103.GA5336@redhat.com
Signed-off-by: Thomas Gleixner

Revert "kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function"

2016-12-08T13:36:18+00:00

This reverts commit 23196f2e5f5d810578a772785807dcdc2b9fdce9.

Now that struct kthread is kmalloc'ed and not longer on the task stack
there is no need anymore to pin the stack.

Signed-off-by: Oleg Nesterov 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Thomas Gleixner 
Cc: Chunming Zhou 
Cc: Roman Pen 
Cc: Petr Mladek 
Cc: Andy Lutomirski 
Cc: Tejun Heo 
Cc: Andy Lutomirski 
Cc: Alex Deucher 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/20161129175100.GA5333@redhat.com
Signed-off-by: Thomas Gleixner

kthread: Make struct kthread kmalloc'ed

2016-12-08T13:36:18+00:00

commit 23196f2e5f5d "kthread: Pin the stack via try_get_task_stack() /
put_task_stack() in to_live_kthread() function" is a workaround for the
fragile design of struct kthread being allocated on the task stack.

struct kthread in its current form should be removed, but this needs
cleanups outside of kthread.c.

As a first step move struct kthread away from the task stack by making it
kmalloc'ed. This allows to access kthread.exited without the magic of
trying to pin task stack and the try logic in to_live_kthread().

Signed-off-by: Oleg Nesterov 
Acked-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Cc: Chunming Zhou 
Cc: Roman Pen 
Cc: Petr Mladek 
Cc: Andy Lutomirski 
Cc: Tejun Heo 
Cc: Andy Lutomirski 
Cc: Alex Deucher 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/20161129175057.GA5330@redhat.com
Signed-off-by: Thomas Gleixner

kthread: better support freezable kthread workers

2016-10-11T22:06:33+00:00

This patch allows to make kthread worker freezable via a new @flags
parameter. It will allow to avoid an init work in some kthreads.

It currently does not affect the function of kthread_worker_fn()
but it might help to do some optimization or fixes eventually.

I currently do not know about any other use for the @flags
parameter but I believe that we will want more flags
in the future.

Finally, I hope that it will not cause confusion with @flags member
in struct kthread. Well, I guess that we will want to rework the
basic kthreads implementation once all kthreads are converted into
kthread workers or workqueues. It is possible that we will merge
the two structures.

Link: http://lkml.kernel.org/r/1470754545-17632-12-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek 
Acked-by: Tejun Heo 
Cc: Oleg Nesterov 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: "Paul E. McKenney" 
Cc: Josh Triplett 
Cc: Thomas Gleixner 
Cc: Jiri Kosina 
Cc: Borislav Petkov 
Cc: Michal Hocko 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds