Messages in this thread Patch in this message | | | Date | Mon, 8 Dec 2008 11:05:11 +0900 | From | Daisuke Nishimura <> | Subject | [PATCH -mmotm 3/4] memcg: avoid dead lock caused by race between oom and cpuset_attach |
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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, dead lock can happen.
This patch avoid this dead lock 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@mxp.nes.nec.co.jp> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu,com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> --- mm/memcontrol.c | 5 +++++ mm/oom_kill.c | 2 -- 2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9877b03..fec4fc3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -51,6 +51,7 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/ #define do_swap_account (0) #endif +static DEFINE_MUTEX(memcg_tasklist); /* can be hold under cgroup_mutex */ /* * Statistics for memory cgroup. @@ -797,7 +798,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, 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; @@ -2173,10 +2176,12 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss, 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 --git a/mm/oom_kill.c b/mm/oom_kill.c index fd150e3..40ba050 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -429,7 +429,6 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask) 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
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