The patch titled
memcg: avoid deadlock caused by race between oom and cpuset_attach
has been removed from the -mm tree. Its filename was
memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: memcg: avoid deadlock caused by race between oom and cpuset_attach
From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
mpol_rebind_mm(), which can be called from cpuset_attach(), does
down_write(mm->mmap_sem). This means down_write(mm->mmap_sem) can be
called under cgroup_mutex.
OTOH, page fault path does down_read(mm->mmap_sem) and calls
mem_cgroup_try_charge_xxx(), which may eventually calls
mem_cgroup_out_of_memory(). And mem_cgroup_out_of_memory() calls
cgroup_lock(). This means cgroup_lock() can be called under
down_read(mm->mmap_sem).
If those two paths race, deadlock can happen.
This patch avoid this deadlock by:
- remove cgroup_lock() from mem_cgroup_out_of_memory().
- define new mutex (memcg_tasklist) and serialize mem_cgroup_move_task()
(->attach handler of memory cgroup) and mem_cgroup_out_of_memory.
Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 5 +++++
mm/oom_kill.c | 2 --
2 files changed, 5 insertions(+), 2 deletions(-)
diff -puN mm/memcontrol.c~memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach
+++ a/mm/memcontrol.c
@@ -51,6 +51,7 @@ static int really_do_swap_account __init
#define do_swap_account (0)
#endif
+static DEFINE_MUTEX(memcg_tasklist); /* can be hold under cgroup_mutex */
/*
* Statistics for memory cgroup.
@@ -827,7 +828,9 @@ static int __mem_cgroup_try_charge(struc
if (!nr_retries--) {
if (oom) {
+ mutex_lock(&memcg_tasklist);
mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
+ mutex_unlock(&memcg_tasklist);
mem_over_limit->last_oom_jiffies = jiffies;
}
goto nomem;
@@ -2211,10 +2214,12 @@ static void mem_cgroup_move_task(struct
struct cgroup *old_cont,
struct task_struct *p)
{
+ mutex_lock(&memcg_tasklist);
/*
* FIXME: It's better to move charges of this process from old
* memcg to new memcg. But it's just on TODO-List now.
*/
+ mutex_unlock(&memcg_tasklist);
}
struct cgroup_subsys mem_cgroup_subsys = {
diff -puN mm/oom_kill.c~memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach mm/oom_kill.c
--- a/mm/oom_kill.c~memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach
+++ a/mm/oom_kill.c
@@ -429,7 +429,6 @@ void mem_cgroup_out_of_memory(struct mem
unsigned long points = 0;
struct task_struct *p;
- cgroup_lock();
read_lock(&tasklist_lock);
retry:
p = select_bad_process(&points, mem);
@@ -444,7 +443,6 @@ retry:
goto retry;
out:
read_unlock(&tasklist_lock);
- cgroup_unlock();
}
#endif
_
Patches currently in -mm which might be from nishimura@xxxxxxxxxxxxxxxxx are
origin.patch
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