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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-10-01 15:44:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-10-01 16:11:12 -0700
commit26251eaf98e26dc2ce2dc26d63bc502700760704 (patch)
treef783cab10c5244c170e7d1a92b6a80c574cdf114 /mm/memcontrol.c
parentuartlite: allow building for timberdale MFD (diff)
downloadlinux-dev-26251eaf98e26dc2ce2dc26d63bc502700760704.tar.xz
linux-dev-26251eaf98e26dc2ce2dc26d63bc502700760704.zip
memcg: fix refcnt going negative
__mem_cgroup_largest_soft_limit_node() returns a mem_cgroup_per_zone "mz" with incremnted mz->mem->css's refcnt. Then, the caller of this function has to call css_put(mz->mem->css). But, mz can be !NULL even if "not found" i.e. without css_get(). By this, css->refcnt will go down to minus. This may cause various things...one of results will be initite-loop in css_tryget() as this. INFO: RCU detected CPU 0 stall (t=10000 jiffies) sending NMI to all CPUs: NMI backtrace for cpu 0 CPU 0: <snip> <<EOE>> <IRQ> [<ffffffff810884bd>] trace_hardirqs_off+0xd/0x10 [<ffffffff8102a940>] flat_send_IPI_mask+0x90/0xb0 [<ffffffff8102a9c9>] flat_send_IPI_all+0x69/0x70 [<ffffffff81027372>] arch_trigger_all_cpu_backtrace+0x62/0xa0 [<ffffffff810bff8e>] __rcu_pending+0x7e/0x370 [<ffffffff810c02c7>] rcu_check_callbacks+0x47/0x130 [<ffffffff81063a26>] update_process_times+0x46/0x70 [<ffffffff81085930>] tick_sched_timer+0x60/0x160 [<ffffffff810858d0>] ? tick_sched_timer+0x0/0x160 [<ffffffff8107a03a>] __run_hrtimer+0xba/0x150 [<ffffffff8107a325>] hrtimer_interrupt+0xd5/0x1b0 [<ffffffff81426dfe>] ? trace_hardirqs_off_thunk+0x3a/0x3c [<ffffffff8142cacd>] smp_apic_timer_interrupt+0x6d/0x9b [<ffffffff8100cb33>] apic_timer_interrupt+0x13/0x20 <EOI> [<ffffffff811317b6>] ? mem_cgroup_walk_tree+0x156/0x180 [<ffffffff811316d3>] ? mem_cgroup_walk_tree+0x73/0x180 [<ffffffff81131692>] ? mem_cgroup_walk_tree+0x32/0x180 [<ffffffff81131a00>] ? mem_cgroup_get_local_stat+0x0/0x110 [<ffffffff81131d5b>] ? mem_control_stat_show+0x14b/0x330 [<ffffffff810a57fd>] ? cgroup_seqfile_show+0x3d/0x60 Above shows CPU0 caught in css_tryget()'s inifinite loop because of bad refcnt. This is a fix to set mz=NULL at the top of retry path. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
-rw-r--r--mm/memcontrol.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e2b98a6875c0..21a30629ca80 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -447,9 +447,10 @@ static struct mem_cgroup_per_zone *
__mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
{
struct rb_node *rightmost = NULL;
- struct mem_cgroup_per_zone *mz = NULL;
+ struct mem_cgroup_per_zone *mz;
retry:
+ mz = NULL;
rightmost = rb_last(&mctz->rb_root);
if (!rightmost)
goto done; /* Nothing to reclaim from */