From: Michal Hocko <mhocko@xxxxxxxx>
After "oom: keep mm of the killed task available" we can safely
detect an oom victim by checking task->signal->oom_mm so we do not need
the signal_struct counter anymore so let's get rid of it.
This alone wouldn't be sufficient for nommu archs because exit_oom_victim
doesn't hide the process from the oom killer anymore. We can, however,
mark the mm with a MMF flag in __mmput. We can reuse MMF_OOM_REAPED and
rename it to a more generic MMF_OOM_SKIP.
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
include/linux/oom.h | 6 ++++++
include/linux/sched.h | 3 +--
kernel/fork.c | 1 +
mm/oom_kill.c | 17 +++++++----------
4 files changed, 15 insertions(+), 12 deletions(-)
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 5bc0457ee3a8..bbe0a7789636 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -72,6 +72,12 @@ static inline bool oom_task_origin(const struct task_struct *p)
extern void mark_oom_victim(struct task_struct *tsk);
+static inline bool tsk_is_oom_victim(struct task_struct * tsk)
+{
+ return tsk->signal->oom_mm;
+}
+
+
#ifdef CONFIG_MMU
extern void wake_oom_reaper(struct task_struct *tsk);
#else
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8943546d52e7..e3376215f4d0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -511,7 +511,7 @@ static inline int get_dumpable(struct mm_struct *mm)
#define MMF_HAS_UPROBES 19 /* has uprobes */
#define MMF_RECALC_UPROBES 20 /* MMF_HAS_UPROBES can be wrong */
-#define MMF_OOM_REAPED 21 /* mm has been already reaped */
+#define MMF_OOM_SKIP 21 /* mm is of no interest for the OOM killer */
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK)
@@ -659,7 +659,6 @@ struct signal_struct {
atomic_t sigcnt;
atomic_t live;
int nr_threads;
- atomic_t oom_victims; /* # of TIF_MEDIE threads in this thread group */
struct list_head thread_head;
wait_queue_head_t wait_chldexit; /* for wait4() */
diff --git a/kernel/fork.c b/kernel/fork.c
index 7e9f83d5fe95..89905b641a0a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -721,6 +721,7 @@ static inline void __mmput(struct mm_struct *mm)
}
if (mm->binfmt)
module_put(mm->binfmt->module);
+ set_bit(MMF_OOM_SKIP, &mm->flags);
mmdrop(mm);
}
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 7f09608405b7..bb4c2ee9c67f 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -181,7 +181,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
*/
adj = (long)p->signal->oom_score_adj;
if (adj == OOM_SCORE_ADJ_MIN ||
- test_bit(MMF_OOM_REAPED, &p->mm->flags) ||
+ test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
in_vfork(p)) {
task_unlock(p);
return 0;
@@ -284,14 +284,14 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
/*
* This task already has access to memory reserves and is being killed.
* Don't allow any other task to have access to the reserves unless
- * the task has MMF_OOM_REAPED because chances that it would release
+ * the task has MMF_OOM_SKIP because chances that it would release
* any memory is quite low.
*/
- if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims)) {
+ if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
struct mm_struct *mm = task->signal->oom_mm;
enum oom_scan_t ret = OOM_SCAN_ABORT;
- if (test_bit(MMF_OOM_REAPED, &mm->flags))
+ if (test_bit(MMF_OOM_SKIP, &mm->flags))
ret = OOM_SCAN_CONTINUE;
return ret;
@@ -565,7 +565,7 @@ static void oom_reap_task(struct task_struct *tsk)
* Hide this mm from OOM killer because it has been either reaped or
* somebody can't call up_write(mmap_sem).
*/
- set_bit(MMF_OOM_REAPED, &mm->flags);
+ set_bit(MMF_OOM_SKIP, &mm->flags);
/* Drop a reference taken by wake_oom_reaper */
put_task_struct(tsk);
@@ -643,8 +643,6 @@ void mark_oom_victim(struct task_struct *tsk)
if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
return;
- atomic_inc(&tsk->signal->oom_victims);
-
/* oom_mm is bound to the signal struct life time. */
if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
atomic_inc(&tsk->signal->oom_mm->mm_count);
@@ -666,7 +664,6 @@ void exit_oom_victim(struct task_struct *tsk)
{
if (!test_and_clear_tsk_thread_flag(tsk, TIF_MEMDIE))
return;
- atomic_dec(&tsk->signal->oom_victims);
if (!atomic_dec_return(&oom_victims))
wake_up_all(&oom_victims_wait);
@@ -758,7 +755,7 @@ bool task_will_free_mem(struct task_struct *task)
* This task has already been drained by the oom reaper so there are
* only small chances it will free some more
*/
- if (test_bit(MMF_OOM_REAPED, &mm->flags))
+ if (test_bit(MMF_OOM_SKIP, &mm->flags))
return false;
if (atomic_read(&mm->mm_users) <= 1)
@@ -898,7 +895,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
* killer to guarantee OOM forward progress.
*/
can_oom_reap = false;
- set_bit(MMF_OOM_REAPED, &mm->flags);
+ set_bit(MMF_OOM_SKIP, &mm->flags);
pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
task_pid_nr(victim), victim->comm,
task_pid_nr(p), p->comm);
--
2.8.1
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