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Message-Id: <20090928180649.b6b7eea9.kamezawa.hiroyu@jp.fujitsu.com>
Date: Mon, 28 Sep 2009 18:06:49 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
mingo@...e.hu,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>
Subject: [BUGFIX][PATCH][rc1] memcg: fix refcnt goes to minus
> At testing my (small) patch, with high memory pressure to
> memcg+hierarchy+softlimit, following is shown.
> ==
> INFO: RCU detected CPU 0 stall (t=10000 jiffies)
> sending NMI to all CPUs:
> NMI backtrace for cpu 0
> CPU 0:
> Modules linked in: sco bridge stp bnep l2cap crc16 bluetooth rfkill iptabl
> e_filter ip_tables ip6table_filter ip6_tables x_tables ipv6 cpufreq_ondemand acpi_cpufreq dm_mirror dm_region_hash dm_log d
> m_multipath dm_mod uinput ppdev i2c_i801 pcspkr i2c_core bnx2 sg e1000e parport_pc parport button shpchp megaraid_sas sd_mo
> d scsi_mod ext3 jbd uhci_hcd ohci_hcd ehci_hcd [last unloaded: microcode]
> Pid: 2886, comm: ruby Not tainted 2.6.31-mm1 #2 PRIMERGY
> RIP: 0010:[<ffffffff810878fe>] [<ffffffff810878fe>] trace_hardirqs_off_ca
> ller+0x3e/0xb RSP: 0018:ffff88004fa03d98 EFLAGS: 00000006
> RAX: 0000000000000046 RBX: 0000000000000c00 RCX: 000000000000e501
> RDX: ffff8806133564f0 RSI: 0000000000000002 RDI: ffffffff8102a940
> RBP: ffff88004fa03d98 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
> R13: 0000000000000046 R14: 00000000000000ff R15: ffff88004fa03f48
> FS: 00007fdeca0856f0(0000) GS:ffff88004fa00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fdeca09e000 CR3: 0000000619fc6000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Call Trace:
> <#DB[1]> <<EOE>> Pid: 2886, comm: ruby Not tainted 2.6.31-mm1 #2
> Call Trace:
> <NMI> [<ffffffff8100af79>] ? show_regs+0x49/0x50
> [<ffffffff81429385>] nmi_watchdog_tick+0x1e5/0x210
> [<ffffffff81428891>] do_nmi+0x1b1/0x2e0
> [<ffffffff8142808a>] nmi+0x1a/0x2c
> [<ffffffff8102a940>] ? flat_send_IPI_mask+0x90/0xb0
> [<ffffffff810878fe>] ? trace_hardirqs_off_caller+0x3e/0xb0
> <<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
> [<ffffffff810a5b90>] ? cgroup_map_add+0x0/0x30
> [<ffffffff8115de03>] ? seq_read+0xf3/0x420
> [<ffffffff811d9926>] ? security_file_permission+0x16/0x20
> [<ffffffff8113b7ec>] ? vfs_read+0xcc/0x190
> [<ffffffff8113b9b5>] ? sys_read+0x55/0x90
> [<ffffffff8100bf9b>] ? system_call_fastpath+0x16/0x1b
> .....
> ==
This is a patch for 2.6.31-rc1 (maybe no hunk with -mm)
==
__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@...fujitsu.com>
---
mm/memcontrol.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
Index: linux-2.6.32-rc1/mm/memcontrol.c
===================================================================
--- linux-2.6.32-rc1.orig/mm/memcontrol.c
+++ linux-2.6.32-rc1/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 */
--
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