--
cgit 1.2-0.3.lf.el7
-From 48744b6339cf649a69b55997e138c17df1ecc897 Mon Sep 17 00:00:00 2001\r
-From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>\r
-Date: Sat, 26 Jan 2019 20:00:51 +0900\r
-Subject: [PATCH] oom, oom_reaper: do not enqueue same task twice\r
-\r
-Arkadiusz reported that enabling memcg's group oom killing causes\r
-strange memcg statistics where there is no task in a memcg despite\r
-the number of tasks in that memcg is not 0. It turned out that there\r
-is a bug in wake_oom_reaper() which allows enqueuing same task twice\r
-which makes impossible to decrease the number of tasks in that memcg\r
-due to a refcount leak.\r
-\r
-This bug existed since the OOM reaper became invokable from\r
-task_will_free_mem(current) path in out_of_memory() in Linux 4.7,\r
-but memcg's group oom killing made it easier to trigger this bug by\r
-calling wake_oom_reaper() on the same task from one out_of_memory()\r
-request.\r
-\r
-Fix this bug using an approach used by commit 855b018325737f76\r
-("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task").\r
-Since task_will_free_mem(p) == false if p->mm == NULL, we can assume that\r
-p->mm != NULL when wake_oom_reaper() is called from task_will_free_mem()\r
-paths. As a side effect of this patch, this patch also avoids enqueuing\r
-multiple threads sharing memory via task_will_free_mem(current) path.\r
-\r
-Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>\r
-Reported-by: Arkadiusz Miśkiewicz <a.miskiewicz@gmail.com>\r
-Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")\r
----\r
- mm/oom_kill.c | 28 +++++++++++++---------------\r
- 1 file changed, 13 insertions(+), 15 deletions(-)\r
-\r
-diff --git a/mm/oom_kill.c b/mm/oom_kill.c\r
-index f0e8cd9..457f240 100644\r
---- a/mm/oom_kill.c\r
-+++ b/mm/oom_kill.c\r
-@@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm)\r
- struct vm_area_struct *vma;\r
- bool ret = true;\r
- \r
-- /*\r
-- * Tell all users of get_user/copy_from_user etc... that the content\r
-- * is no longer stable. No barriers really needed because unmapping\r
-- * should imply barriers already and the reader would hit a page fault\r
-- * if it stumbled over a reaped memory.\r
-- */\r
-- set_bit(MMF_UNSTABLE, &mm->flags);\r
--\r
- for (vma = mm->mmap ; vma; vma = vma->vm_next) {\r
- if (!can_madv_dontneed_vma(vma))\r
- continue;\r
-@@ -645,10 +637,15 @@ static int oom_reaper(void *unused)\r
- return 0;\r
- }\r
- \r
--static void wake_oom_reaper(struct task_struct *tsk)\r
-+static void wake_oom_reaper(struct task_struct *tsk, struct mm_struct *mm)\r
- {\r
-- /* tsk is already queued? */\r
-- if (tsk == oom_reaper_list || tsk->oom_reaper_list)\r
-+ /*\r
-+ * Tell all users of get_user/copy_from_user etc... that the content\r
-+ * is no longer stable. No barriers really needed because unmapping\r
-+ * should imply barriers already and the reader would hit a page fault\r
-+ * if it stumbled over a reaped memory.\r
-+ */\r
-+ if (test_and_set_bit(MMF_UNSTABLE, &mm->flags))\r
- return;\r
- \r
- get_task_struct(tsk);\r
-@@ -668,7 +665,8 @@ static int __init oom_init(void)\r
- }\r
- subsys_initcall(oom_init)\r
- #else\r
--static inline void wake_oom_reaper(struct task_struct *tsk)\r
-+static inline void wake_oom_reaper(struct task_struct *tsk,\r
-+ struct mm_struct *mm)\r
- {\r
- }\r
- #endif /* CONFIG_MMU */\r
-@@ -915,7 +913,7 @@ static void __oom_kill_process(struct task_struct *victim)\r
- rcu_read_unlock();\r
- \r
- if (can_oom_reap)\r
-- wake_oom_reaper(victim);\r
-+ wake_oom_reaper(victim, mm);\r
- \r
- mmdrop(mm);\r
- put_task_struct(victim);\r
-@@ -955,7 +953,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message)\r
- task_lock(p);\r
- if (task_will_free_mem(p)) {\r
- mark_oom_victim(p);\r
-- wake_oom_reaper(p);\r
-+ wake_oom_reaper(p, p->mm);\r
- task_unlock(p);\r
- put_task_struct(p);\r
- return;\r
-@@ -1085,7 +1083,7 @@ bool out_of_memory(struct oom_control *oc)\r
- */\r
- if (task_will_free_mem(current)) {\r
- mark_oom_victim(current);\r
-- wake_oom_reaper(current);\r
-+ wake_oom_reaper(current, current->mm);\r
- return true;\r
- }\r
- \r
--- \r
-1.8.3.1\r
-\r
+
+From 9c9e935fc038342c48461aabca666f1b544e32b1 Mon Sep 17 00:00:00 2001
+From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
+Date: Sat, 26 Jan 2019 21:57:25 +0900
+Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice
+
+Arkadiusz reported that enabling memcg's group oom killing causes
+strange memcg statistics where there is no task in a memcg despite
+the number of tasks in that memcg is not 0. It turned out that there
+is a bug in wake_oom_reaper() which allows enqueuing same task twice
+which makes impossible to decrease the number of tasks in that memcg
+due to a refcount leak.
+
+This bug existed since the OOM reaper became invokable from
+task_will_free_mem(current) path in out_of_memory() in Linux 4.7,
+but memcg's group oom killing made it easier to trigger this bug by
+calling wake_oom_reaper() on the same task from one out_of_memory()
+request.
+
+Fix this bug using an approach used by commit 855b018325737f76
+("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task").
+As a side effect of this patch, this patch also avoids enqueuing
+multiple threads sharing memory via task_will_free_mem(current) path.
+
+Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
+Reported-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
+Tested-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
+Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")
+---
+ mm/oom_kill.c | 17 +++++++----------
+ 1 file changed, 7 insertions(+), 10 deletions(-)
+
+diff --git a/mm/oom_kill.c b/mm/oom_kill.c
+index f0e8cd9..057bfee 100644
+--- a/mm/oom_kill.c
++++ b/mm/oom_kill.c
+@@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm)
+ struct vm_area_struct *vma;
+ bool ret = true;
+
+- /*
+- * Tell all users of get_user/copy_from_user etc... that the content
+- * is no longer stable. No barriers really needed because unmapping
+- * should imply barriers already and the reader would hit a page fault
+- * if it stumbled over a reaped memory.
+- */
+- set_bit(MMF_UNSTABLE, &mm->flags);
+-
+ for (vma = mm->mmap ; vma; vma = vma->vm_next) {
+ if (!can_madv_dontneed_vma(vma))
+ continue;
+@@ -647,8 +639,13 @@ static int oom_reaper(void *unused)
+
+ static void wake_oom_reaper(struct task_struct *tsk)
+ {
+- /* tsk is already queued? */
+- if (tsk == oom_reaper_list || tsk->oom_reaper_list)
++ /*
++ * Tell all users of get_user/copy_from_user etc... that the content
++ * is no longer stable. No barriers really needed because unmapping
++ * should imply barriers already and the reader would hit a page fault
++ * if it stumbled over a reaped memory.
++ */
++ if (test_and_set_bit(MMF_UNSTABLE, &tsk->signal->oom_mm->flags))
+ return;
+
+ get_task_struct(tsk);
+--
+1.8.3.1
+
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