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authorDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>2009-01-07 18:08:29 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-08 08:31:09 -0800
commit7f4d454dee2e0bdd21bafd413d1c53e443a26540 (patch)
treeabf54c2bd7c91fe09685e42b3a92d84679403058
parenta5e924f5f8abf97944e625d74967cc9452cfbce8 (diff)
memcg: avoid deadlock caused by race between oom and cpuset_attach
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@mxp.nes.nec.co.jp> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/memcontrol.c5
-rw-r--r--mm/oom_kill.c2
2 files changed, 5 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 435f08dac8b..861037070f6 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.
@@ -827,7 +828,9 @@ 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;
@@ -2211,10 +2214,12 @@ 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 fd150e3a256..40ba05061a4 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