>From 5fbd16cffd5dc51f9ba8591fc18d315ff6ff9b96 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Fri, 8 Jul 2016 00:33:13 +0900
Subject: [PATCH 3/6] mm,oom: Use list of mm_struct used by OOM victims.
Currently, we walk process list in order to find existing TIF_MEMDIE
threads. But if we remember list of mm_struct used by TIF_MEMDIE threads,
we can avoid walking process list. Next patch in this series allows
OOM reaper to use list of mm_struct introduced by this patch.
This patch reverts commit e2fe14564d3316d1 ("oom_reaper: close race with
exiting task") because oom_has_pending_mm() will prevent that race.
Since CONFIG_MMU=y kernel has OOM reaper callback hook which can remove
mm_struct from the list, let the OOM reaper call exit_oom_mm(mm). This
patch temporarily fails to call exit_oom_mm(mm) when find_lock_task_mm()
in oom_reap_task() failed. It will be fixed by next patch.
But since CONFIG_MMU=n kernel does not have OOM reaper callback hook,
call exit_oom_mm(mm) from __mmput(mm) if that mm is used by OOM victims.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
include/linux/mm_types.h | 7 +++++
include/linux/oom.h | 3 ++
kernel/fork.c | 4 +++
mm/memcontrol.c | 5 ++++
mm/oom_kill.c | 72 +++++++++++++++++++++++++++++++-----------------
5 files changed, 66 insertions(+), 25 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index e093e1d..7c1370a 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -392,6 +392,12 @@ struct mm_rss_stat {
atomic_long_t count[NR_MM_COUNTERS];
};
+struct oom_mm {
+ struct list_head list; /* Linked to oom_mm_list list. */
+ /* Thread which was passed to mark_oom_victim() for the last time. */
+ struct task_struct *victim;
+};
+
struct kioctx_table;
struct mm_struct {
struct vm_area_struct *mmap; /* list of VMAs */
@@ -515,6 +521,7 @@ struct mm_struct {
#ifdef CONFIG_HUGETLB_PAGE
atomic_long_t hugetlb_usage;
#endif
+ struct oom_mm oom_mm;
#ifdef CONFIG_MMU
struct work_struct async_put_work;
#endif
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 5bc0457..bdcb331 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -91,6 +91,9 @@ extern void oom_kill_process(struct oom_control *oc, struct task_struct *p,
extern void check_panic_on_oom(struct oom_control *oc,
enum oom_constraint constraint);
+extern void exit_oom_mm(struct mm_struct *mm);
+extern bool oom_has_pending_mm(struct mem_cgroup *memcg,
+ const nodemask_t *nodemask);
extern enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
struct task_struct *task);
diff --git a/kernel/fork.c b/kernel/fork.c
index 7926993..8e469e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -722,6 +722,10 @@ static inline void __mmput(struct mm_struct *mm)
}
if (mm->binfmt)
module_put(mm->binfmt->module);
+#ifndef CONFIG_MMU
+ if (mm->oom_mm.victim)
+ exit_oom_mm(mm);
+#endif
mmdrop(mm);
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 40dfca3..8f7a5b7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1241,6 +1241,11 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
}
check_panic_on_oom(&oc, CONSTRAINT_MEMCG);
+ if (oom_has_pending_mm(memcg, NULL)) {
+ /* Set a dummy value to return "true". */
+ chosen = (void *) 1;
+ goto unlock;
+ }
totalpages = mem_cgroup_get_limit(memcg) ? : 1;
for_each_mem_cgroup_tree(iter, memcg) {
struct css_task_iter it;
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 9f0022e..87e7ff3 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -275,6 +275,28 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc,
}
#endif
+static LIST_HEAD(oom_mm_list);
+
+void exit_oom_mm(struct mm_struct *mm)
+{
+ mutex_lock(&oom_lock);
+ list_del(&mm->oom_mm.list);
+ put_task_struct(mm->oom_mm.victim);
+ mm->oom_mm.victim = NULL;
+ mmdrop(mm);
+ mutex_unlock(&oom_lock);
+}
+
+bool oom_has_pending_mm(struct mem_cgroup *memcg, const nodemask_t *nodemask)
+{
+ struct mm_struct *mm;
+
+ list_for_each_entry(mm, &oom_mm_list, oom_mm.list)
+ if (!oom_unkillable_task(mm->oom_mm.victim, memcg, nodemask))
+ return true;
+ return false;
+}
+
enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
struct task_struct *task)
{
@@ -458,28 +480,9 @@ static bool __oom_reap_task(struct task_struct *tsk, struct mm_struct *mm)
struct vm_area_struct *vma;
struct zap_details details = {.check_swap_entries = true,
.ignore_dirty = true};
- bool ret = true;
- /*
- * 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
- * mmget_not_zero
- * mmput
- * atomic_dec_and_test
- * exit_oom_victim
- * [...]
- * out_of_memory
- * select_bad_process
- * # no TIF_MEMDIE task selects new victim
- * unmap_page_range # frees some memory
- */
- mutex_lock(&oom_lock);
-
- if (!down_read_trylock(&mm->mmap_sem)) {
- ret = false;
- goto unlock_oom;
- }
+ if (!down_read_trylock(&mm->mmap_sem))
+ return false;
/*
* increase mm_users only after we know we will reap something so
@@ -488,7 +491,7 @@ static bool __oom_reap_task(struct task_struct *tsk, struct mm_struct *mm)
*/
if (!mmget_not_zero(mm)) {
up_read(&mm->mmap_sem);
- goto unlock_oom;
+ return true;
}
tlb_gather_mmu(&tlb, mm, 0, -1);
@@ -536,9 +539,7 @@ static bool __oom_reap_task(struct task_struct *tsk, struct mm_struct *mm)
* put the oom_reaper out of the way.
*/
mmput_async(mm);
-unlock_oom:
- mutex_unlock(&oom_lock);
- return ret;
+ return true;
}
#define MAX_OOM_REAP_RETRIES 10
@@ -586,6 +587,9 @@ done:
/* Drop a reference taken by wake_oom_reaper */
put_task_struct(tsk);
+ /* Drop references taken by mark_oom_victim() */
+ if (mm)
+ exit_oom_mm(mm);
/* Drop a reference taken above. */
if (mm)
mmdrop(mm);
@@ -653,6 +657,9 @@ subsys_initcall(oom_init)
*/
void mark_oom_victim(struct task_struct *tsk)
{
+ struct mm_struct *mm = tsk->mm;
+ struct task_struct *old_tsk = mm->oom_mm.victim;
+
WARN_ON(oom_killer_disabled);
/* OOM killer might race with memcg OOM */
if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
@@ -666,6 +673,18 @@ void mark_oom_victim(struct task_struct *tsk)
*/
__thaw_task(tsk);
atomic_inc(&oom_victims);
+ /*
+ * Since mark_oom_victim() is called from multiple threads,
+ * connect this mm to oom_mm_list only if not yet connected.
+ */
+ get_task_struct(tsk);
+ mm->oom_mm.victim = tsk;
+ if (!old_tsk) {
+ atomic_inc(&mm->mm_count);
+ list_add_tail(&mm->oom_mm.list, &oom_mm_list);
+ } else {
+ put_task_struct(old_tsk);
+ }
}
/**
@@ -1026,6 +1045,9 @@ bool out_of_memory(struct oom_control *oc)
return true;
}
+ if (!is_sysrq_oom(oc) && oom_has_pending_mm(oc->memcg, oc->nodemask))
+ return true;
+
p = select_bad_process(oc, &points, totalpages);
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!p && !is_sysrq_oom(oc)) {
--
1.8.3.1
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