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Commit 431f42fd authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds
Browse files

mm/oom_kill.c: clean up oom_reap_task_mm() 

Andrew has noticed some inconsistencies in oom_reap_task_mm.  Notably

 - Undocumented return value.

 - comment "failed to reap part..." is misleading - sounds like it's
   referring to something which happened in the past, is in fact
   referring to something which might happen in the future.

 - fails to call trace_finish_task_reaping() in one case

 - code duplication.

 - Increases mmap_sem hold time a little by moving
   trace_finish_task_reaping() inside the locked region.  So sue me ;)

 - Sharing the finish: path means that the trace event won't
   distinguish between the two sources of finishing.

Add a short explanation for the return value and fix the rest by
reorganizing the function a bit to have unified function exit paths.

Link: http://lkml.kernel.org/r/20180724141747.GP28386@dhcp22.suse.cz


Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c3b78b11

mm/oom_kill.c

+16 −8
Original line number Diff line number Diff line
@@ -534,8 +534,16 @@ bool __oom_reap_task_mm(struct mm_struct *mm) 
	return ret;

}



/*

 * Reaps the address space of the give task.

 *

 * Returns true on success and false if none or part of the address space

 * has been reclaimed and the caller should retry later.

 */

static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)

{

	bool ret = true;



	if (!down_read_trylock(&mm->mmap_sem)) {

		trace_skip_task_reaping(tsk->pid);

		return false;
@@ -548,28 +556,28 @@ static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) 
	 * down_write();up_write() cycle in exit_mmap().

	 */

	if (test_bit(MMF_OOM_SKIP, &mm->flags)) {

		up_read(&mm->mmap_sem);

		trace_skip_task_reaping(tsk->pid);

		return true;

		goto out_unlock;

	}



	trace_start_task_reaping(tsk->pid);



	/* failed to reap part of the address space. Try again later */

	if (!__oom_reap_task_mm(mm)) {

		up_read(&mm->mmap_sem);

		return false;

	}

	ret = __oom_reap_task_mm(mm);

	if (!ret)

		goto out_finish;



	pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",

			task_pid_nr(tsk), tsk->comm,

			K(get_mm_counter(mm, MM_ANONPAGES)),

			K(get_mm_counter(mm, MM_FILEPAGES)),

			K(get_mm_counter(mm, MM_SHMEMPAGES)));

out_finish:

	trace_finish_task_reaping(tsk->pid);

out_unlock:

	up_read(&mm->mmap_sem);



	trace_finish_task_reaping(tsk->pid);

	return true;

	return ret;

}



#define MAX_OOM_REAP_RETRIES 10