diff options
author | Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> | 2016-10-07 16:58:45 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-07 18:46:27 -0700 |
commit | 7ebffa45551fe7db86a2b32bf586f124ef484e6e (patch) | |
tree | 2c58c3c7ef2d09ad69067b57488e3ef232e2914c | |
parent | 6b53491598a4d9694318e6e2b11d8c9988a483d4 (diff) | |
download | linux-7ebffa45551fe7db86a2b32bf586f124ef484e6e.tar.bz2 |
mm,oom_reaper: reduce find_lock_task_mm() usage
Patch series "fortify oom killer even more", v2.
This patch (of 9):
__oom_reap_task() can be simplified a bit if it receives a valid mm from
oom_reap_task() which also uses that mm when __oom_reap_task() failed.
We can drop one find_lock_task_mm() call and also make the
__oom_reap_task() code flow easier to follow. Moreover, this will make
later patch in the series easier to review. Pinning mm's mm_count for
longer time is not really harmful because this will not pin much memory.
This patch doesn't introduce any functional change.
Link: http://lkml.kernel.org/r/1472119394-11342-2-git-send-email-mhocko@kernel.org
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/oom_kill.c | 81 |
1 files changed, 38 insertions, 43 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 463cdd22d4e0..87fad956c96b 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -463,12 +463,10 @@ static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait); static struct task_struct *oom_reaper_list; static DEFINE_SPINLOCK(oom_reaper_lock); -static bool __oom_reap_task(struct task_struct *tsk) +static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) { struct mmu_gather tlb; struct vm_area_struct *vma; - struct mm_struct *mm = NULL; - struct task_struct *p; struct zap_details details = {.check_swap_entries = true, .ignore_dirty = true}; bool ret = true; @@ -476,7 +474,7 @@ static bool __oom_reap_task(struct task_struct *tsk) /* * We have to make sure to not race with the victim exit path * and cause premature new oom victim selection: - * __oom_reap_task exit_mm + * __oom_reap_task_mm exit_mm * mmget_not_zero * mmput * atomic_dec_and_test @@ -489,22 +487,9 @@ static bool __oom_reap_task(struct task_struct *tsk) */ mutex_lock(&oom_lock); - /* - * Make sure we find the associated mm_struct even when the particular - * thread has already terminated and cleared its mm. - * We might have race with exit path so consider our work done if there - * is no mm. - */ - p = find_lock_task_mm(tsk); - if (!p) - goto unlock_oom; - mm = p->mm; - atomic_inc(&mm->mm_count); - task_unlock(p); - if (!down_read_trylock(&mm->mmap_sem)) { ret = false; - goto mm_drop; + goto unlock_oom; } /* @@ -514,7 +499,7 @@ static bool __oom_reap_task(struct task_struct *tsk) */ if (!mmget_not_zero(mm)) { up_read(&mm->mmap_sem); - goto mm_drop; + goto unlock_oom; } tlb_gather_mmu(&tlb, mm, 0, -1); @@ -562,8 +547,6 @@ static bool __oom_reap_task(struct task_struct *tsk) * put the oom_reaper out of the way. */ mmput_async(mm); -mm_drop: - mmdrop(mm); unlock_oom: mutex_unlock(&oom_lock); return ret; @@ -573,36 +556,45 @@ unlock_oom: static void oom_reap_task(struct task_struct *tsk) { int attempts = 0; + struct mm_struct *mm = NULL; + struct task_struct *p = find_lock_task_mm(tsk); + + /* + * Make sure we find the associated mm_struct even when the particular + * thread has already terminated and cleared its mm. + * We might have race with exit path so consider our work done if there + * is no mm. + */ + if (!p) + goto done; + mm = p->mm; + atomic_inc(&mm->mm_count); + task_unlock(p); /* Retry the down_read_trylock(mmap_sem) a few times */ - while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task(tsk)) + while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task_mm(tsk, mm)) schedule_timeout_idle(HZ/10); - if (attempts > MAX_OOM_REAP_RETRIES) { - struct task_struct *p; + if (attempts <= MAX_OOM_REAP_RETRIES) + goto done; - pr_info("oom_reaper: unable to reap pid:%d (%s)\n", - task_pid_nr(tsk), tsk->comm); + pr_info("oom_reaper: unable to reap pid:%d (%s)\n", + task_pid_nr(tsk), tsk->comm); - /* - * If we've already tried to reap this task in the past and - * failed it probably doesn't make much sense to try yet again - * so hide the mm from the oom killer so that it can move on - * to another task with a different mm struct. - */ - p = find_lock_task_mm(tsk); - if (p) { - if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &p->mm->flags)) { - pr_info("oom_reaper: giving up pid:%d (%s)\n", - task_pid_nr(tsk), tsk->comm); - set_bit(MMF_OOM_REAPED, &p->mm->flags); - } - task_unlock(p); - } - - debug_show_all_locks(); + /* + * If we've already tried to reap this task in the past and + * failed it probably doesn't make much sense to try yet again + * so hide the mm from the oom killer so that it can move on + * to another task with a different mm struct. + */ + if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &mm->flags)) { + pr_info("oom_reaper: giving up pid:%d (%s)\n", + task_pid_nr(tsk), tsk->comm); + set_bit(MMF_OOM_REAPED, &mm->flags); } + debug_show_all_locks(); +done: /* * Clear TIF_MEMDIE because the task shouldn't be sitting on a * reasonably reclaimable memory anymore or it is not a good candidate @@ -614,6 +606,9 @@ static void oom_reap_task(struct task_struct *tsk) /* Drop a reference taken by wake_oom_reaper */ put_task_struct(tsk); + /* Drop a reference taken above. */ + if (mm) + mmdrop(mm); } static int oom_reaper(void *unused) |