From: Michal Hocko <mhocko@kernel.org>
To: Roman Gushchin <guro@fb.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-kernel@vger.kernel.org, kernel-team@fb.com,
stable@vger.kernel.org, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 1/2] mm: memcg: switch to css_tryget() in get_mem_cgroup_from_mm()
Date: Thu, 7 Nov 2019 13:21:25 +0100 [thread overview]
Message-ID: <20191107122125.GS8314@dhcp22.suse.cz> (raw)
In-Reply-To: <20191106225131.3543616-1-guro@fb.com>
On Wed 06-11-19 14:51:30, Roman Gushchin wrote:
> We've encountered a rcu stall in get_mem_cgroup_from_mm():
>
> rcu: INFO: rcu_sched self-detected stall on CPU
> rcu: 33-....: (21000 ticks this GP) idle=6c6/1/0x4000000000000002 softirq=35441/35441 fqs=5017
> (t=21031 jiffies g=324821 q=95837) NMI backtrace for cpu 33
> <...>
> RIP: 0010:get_mem_cgroup_from_mm+0x2f/0x90
> <...>
> __memcg_kmem_charge+0x55/0x140
> __alloc_pages_nodemask+0x267/0x320
> pipe_write+0x1ad/0x400
> new_sync_write+0x127/0x1c0
> __kernel_write+0x4f/0xf0
> dump_emit+0x91/0xc0
> writenote+0xa0/0xc0
> elf_core_dump+0x11af/0x1430
> do_coredump+0xc65/0xee0
> ? unix_stream_sendmsg+0x37d/0x3b0
> get_signal+0x132/0x7c0
> do_signal+0x36/0x640
> ? recalc_sigpending+0x17/0x50
> exit_to_usermode_loop+0x61/0xd0
> do_syscall_64+0xd4/0x100
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> The problem is caused by an exiting task which is associated with
> an offline memcg.
Hmm, how can we have a task in an offline memcg? I thought that any
existing task will prevent cgroup removal from proceeding. Is this some
sort of race where the task managed to disassociate from the cgroup
while there is still a binding to a memcg existing? What am I missing?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-11-07 12:21 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 22:51 [PATCH 1/2] mm: memcg: switch to css_tryget() in get_mem_cgroup_from_mm() Roman Gushchin
2019-11-06 22:51 ` [PATCH 2/2] mm: hugetlb: switch to css_tryget() in hugetlb_cgroup_charge_cgroup() Roman Gushchin
2019-11-07 0:26 ` Johannes Weiner
2019-11-07 2:31 ` Shakeel Butt
2019-11-07 15:44 ` Tejun Heo
2019-11-07 0:22 ` [PATCH 1/2] mm: memcg: switch to css_tryget() in get_mem_cgroup_from_mm() Johannes Weiner
2019-11-07 1:25 ` Shakeel Butt
2019-11-07 1:43 ` Johannes Weiner
2019-11-07 1:43 ` Roman Gushchin
2019-11-07 2:21 ` Shakeel Butt
2019-11-07 2:28 ` Shakeel Butt
2019-11-07 12:21 ` Michal Hocko [this message]
2019-11-07 15:43 ` Tejun Heo
2019-11-07 16:42 ` Roman Gushchin
2019-11-07 17:02 ` Michal Hocko
2019-11-07 22:41 ` Roman Gushchin
2019-11-08 8:53 ` Michal Hocko
2019-11-07 15:43 ` Tejun Heo
2019-11-13 16:29 ` Michal Koutný
2019-11-13 17:08 ` Roman Gushchin
2019-11-14 19:16 ` Michal Hocko
2019-11-14 19:20 ` Tejun Heo
2019-11-14 19:33 ` Michal Hocko
2019-11-14 19:37 ` Tejun Heo
2019-11-15 17:40 ` Michal Hocko
2019-11-15 17:45 ` Tejun Heo
2019-11-15 17:47 ` Michal Hocko
2019-11-15 17:48 ` Tejun Heo
2019-11-15 18:03 ` Michal Hocko
2019-11-15 18:07 ` Roman Gushchin
2019-11-18 9:43 ` Michal Hocko
2019-11-15 18:13 ` Roman Gushchin
2019-11-21 15:28 ` Michal Koutný
2019-11-22 8:20 ` Michal Hocko
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