>From ce97a7f6b94a6003bc2b41e5f69da2fedc934a9d Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 2 Jul 2016 23:10:06 +0900
Subject: [PATCH 8/8] mm,oom_reaper: Make OOM reaper use list of mm_struct.
Since OOM reaping is per mm_struct operation, it is natural to use
list of mm_struct used by OOM victims.
This patch eliminates find_lock_task_mm() usage from the OOM reaper.
This patch fixes what commit 36324a990cf578b5 ("oom: clear TIF_MEMDIE
after oom_reaper managed to unmap the address space") and
commit 449d777d7ad6d7f9 ("mm, oom_reaper: clear TIF_MEMDIE for all tasks
queued for oom_reaper") tried to address, by always calling exit_oom_mm()
after OOM reap attempt was made.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
include/linux/oom.h | 8 -----
include/linux/sched.h | 3 --
mm/memcontrol.c | 1 -
mm/oom_kill.c | 84 +++++++++++++++++----------------------------------
4 files changed, 27 insertions(+), 69 deletions(-)
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 4844325..1a212c1 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -71,14 +71,6 @@ static inline bool oom_task_origin(const struct task_struct *p)
extern void mark_oom_victim(struct task_struct *tsk, struct oom_control *oc);
-#ifdef CONFIG_MMU
-extern void wake_oom_reaper(struct task_struct *tsk);
-#else
-static inline void wake_oom_reaper(struct task_struct *tsk)
-{
-}
-#endif
-
extern unsigned long oom_badness(struct task_struct *p,
struct mem_cgroup *memcg, const nodemask_t *nodemask,
unsigned long totalpages);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f472f27..4379279 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1916,9 +1916,6 @@ struct task_struct {
unsigned long task_state_change;
#endif
int pagefault_disabled;
-#ifdef CONFIG_MMU
- struct task_struct *oom_reaper_list;
-#endif
/* CPU-specific state of this task */
struct thread_struct thread;
/*
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c17160d..9acc840 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1236,7 +1236,6 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
*/
if (task_will_free_mem(current)) {
mark_oom_victim(current, &oc);
- wake_oom_reaper(current);
goto unlock;
}
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 317ce2c..bdc192f 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -468,8 +468,6 @@ bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
* victim (if that is possible) to help the OOM killer to move on.
*/
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_vmas(struct mm_struct *mm)
{
@@ -540,30 +538,27 @@ static bool __oom_reap_vmas(struct mm_struct *mm)
}
#define MAX_OOM_REAP_RETRIES 10
-static void oom_reap_task(struct task_struct *tsk)
+static void oom_reap_vmas(struct mm_struct *mm)
{
int attempts = 0;
- struct mm_struct *mm = NULL;
- struct task_struct *p = find_lock_task_mm(tsk);
+ bool ret;
/*
- * 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.
+ * Check MMF_OOM_REAPED after holding oom_lock because
+ * oom_kill_process() might find this mm pinned.
*/
- if (!p)
- goto done;
- mm = p->mm;
- atomic_inc(&mm->mm_count);
- task_unlock(p);
+ mutex_lock(&oom_lock);
+ ret = test_bit(MMF_OOM_REAPED, &mm->flags);
+ mutex_unlock(&oom_lock);
+ if (ret)
+ return;
/* Retry the down_read_trylock(mmap_sem) a few times */
while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_vmas(mm))
schedule_timeout_idle(HZ/10);
if (attempts <= MAX_OOM_REAP_RETRIES)
- goto done;
+ return;
pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
mm->oom_mm.pid, mm->oom_mm.comm);
@@ -580,51 +575,30 @@ static void oom_reap_task(struct task_struct *tsk)
set_bit(MMF_OOM_REAPED, &mm->flags);
}
debug_show_all_locks();
-
-done:
- tsk->oom_reaper_list = NULL;
- /* 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)
{
while (true) {
- struct task_struct *tsk = NULL;
-
- wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
- spin_lock(&oom_reaper_lock);
- if (oom_reaper_list != NULL) {
- tsk = oom_reaper_list;
- oom_reaper_list = tsk->oom_reaper_list;
- }
- spin_unlock(&oom_reaper_lock);
-
- if (tsk)
- oom_reap_task(tsk);
+ struct mm_struct *mm = NULL;
+
+ wait_event_freezable(oom_reaper_wait,
+ !list_empty(&oom_mm_list));
+ spin_lock(&oom_mm_lock);
+ if (!list_empty(&oom_mm_list))
+ mm = list_first_entry(&oom_mm_list, struct mm_struct,
+ oom_mm.list);
+ spin_unlock(&oom_mm_lock);
+ if (!mm)
+ continue;
+ oom_reap_vmas(mm);
+ /* Drop a reference taken by mark_oom_victim(). */
+ exit_oom_mm(mm);
}
return 0;
}
-void wake_oom_reaper(struct task_struct *tsk)
-{
- /* tsk is already queued? */
- if (tsk == oom_reaper_list || tsk->oom_reaper_list)
- return;
-
- get_task_struct(tsk);
-
- spin_lock(&oom_reaper_lock);
- tsk->oom_reaper_list = oom_reaper_list;
- oom_reaper_list = tsk;
- spin_unlock(&oom_reaper_lock);
- wake_up(&oom_reaper_wait);
-}
-
static int __init oom_init(void)
{
kthread_run(oom_reaper, NULL, "oom_reaper");
@@ -667,6 +641,9 @@ void mark_oom_victim(struct task_struct *tsk, struct oom_control *oc)
mm->oom_mm.pid = task_pid_nr(tsk);
#endif
list_add_tail(&mm->oom_mm.list, &oom_mm_list);
+#ifdef CONFIG_MMU
+ wake_up(&oom_reaper_wait);
+#endif
}
spin_unlock(&oom_mm_lock);
/*
@@ -816,7 +793,6 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
unsigned int victim_points = 0;
static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
DEFAULT_RATELIMIT_BURST);
- bool can_oom_reap = true;
/*
* If the task is already exiting, don't alarm the sysadmin or kill
@@ -825,7 +801,6 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
task_lock(p);
if (task_will_free_mem(p)) {
mark_oom_victim(p, oc);
- wake_oom_reaper(p);
task_unlock(p);
put_task_struct(p);
return;
@@ -915,7 +890,6 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
* memory might be still used. Hide the mm from the oom
* killer to guarantee OOM forward progress.
*/
- can_oom_reap = false;
set_bit(MMF_OOM_REAPED, &mm->flags);
pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
task_pid_nr(victim), victim->comm,
@@ -926,9 +900,6 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
}
rcu_read_unlock();
- if (can_oom_reap)
- wake_oom_reaper(victim);
-
mmdrop(mm);
put_task_struct(victim);
}
@@ -1004,7 +975,6 @@ bool out_of_memory(struct oom_control *oc)
*/
if (task_will_free_mem(current)) {
mark_oom_victim(current, oc);
- wake_oom_reaper(current);
return true;
}
--
1.8.3.1
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