Add fix for known cgroup deadlock
This commit is contained in:
Laura Abbott
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32675a43b4
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From 568ac888215c7fb2fabe8ea739b00ec3c1f5d440 Mon Sep 17 00:00:00 2001
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From: Balbir Singh <bsingharora@gmail.com>
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Date: Wed, 10 Aug 2016 15:43:06 -0400
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Subject: [PATCH] cgroup: reduce read locked section of
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cgroup_threadgroup_rwsem during fork
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cgroup_threadgroup_rwsem is acquired in read mode during process exit
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and fork. It is also grabbed in write mode during
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__cgroups_proc_write(). I've recently run into a scenario with lots
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of memory pressure and OOM and I am beginning to see
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systemd
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__switch_to+0x1f8/0x350
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__schedule+0x30c/0x990
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schedule+0x48/0xc0
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percpu_down_write+0x114/0x170
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__cgroup_procs_write.isra.12+0xb8/0x3c0
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cgroup_file_write+0x74/0x1a0
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kernfs_fop_write+0x188/0x200
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__vfs_write+0x6c/0xe0
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vfs_write+0xc0/0x230
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SyS_write+0x6c/0x110
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system_call+0x38/0xb4
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This thread is waiting on the reader of cgroup_threadgroup_rwsem to
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exit. The reader itself is under memory pressure and has gone into
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reclaim after fork. There are times the reader also ends up waiting on
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oom_lock as well.
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__switch_to+0x1f8/0x350
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__schedule+0x30c/0x990
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schedule+0x48/0xc0
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jbd2_log_wait_commit+0xd4/0x180
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ext4_evict_inode+0x88/0x5c0
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evict+0xf8/0x2a0
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dispose_list+0x50/0x80
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prune_icache_sb+0x6c/0x90
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super_cache_scan+0x190/0x210
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shrink_slab.part.15+0x22c/0x4c0
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shrink_zone+0x288/0x3c0
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do_try_to_free_pages+0x1dc/0x590
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try_to_free_pages+0xdc/0x260
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__alloc_pages_nodemask+0x72c/0xc90
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alloc_pages_current+0xb4/0x1a0
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page_table_alloc+0xc0/0x170
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__pte_alloc+0x58/0x1f0
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copy_page_range+0x4ec/0x950
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copy_process.isra.5+0x15a0/0x1870
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_do_fork+0xa8/0x4b0
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ppc_clone+0x8/0xc
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In the meanwhile, all processes exiting/forking are blocked almost
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stalling the system.
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This patch moves the threadgroup_change_begin from before
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cgroup_fork() to just before cgroup_canfork(). There is no nee to
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worry about threadgroup changes till the task is actually added to the
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threadgroup. This avoids having to call reclaim with
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cgroup_threadgroup_rwsem held.
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tj: Subject and description edits.
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Signed-off-by: Balbir Singh <bsingharora@gmail.com>
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Acked-by: Zefan Li <lizefan@huawei.com>
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Cc: Oleg Nesterov <oleg@redhat.com>
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Cc: Andrew Morton <akpm@linux-foundation.org>
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Cc: stable@vger.kernel.org # v4.2+
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Signed-off-by: Tejun Heo <tj@kernel.org>
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---
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kernel/fork.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/kernel/fork.c b/kernel/fork.c
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index 52e725d..aaf7823 100644
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--- a/kernel/fork.c
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+++ b/kernel/fork.c
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@@ -1404,7 +1404,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
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p->real_start_time = ktime_get_boot_ns();
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p->io_context = NULL;
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p->audit_context = NULL;
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- threadgroup_change_begin(current);
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cgroup_fork(p);
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#ifdef CONFIG_NUMA
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p->mempolicy = mpol_dup(p->mempolicy);
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@@ -1556,6 +1555,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
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INIT_LIST_HEAD(&p->thread_group);
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p->task_works = NULL;
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+ threadgroup_change_begin(current);
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/*
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* Ensure that the cgroup subsystem policies allow the new process to be
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* forked. It should be noted the the new process's css_set can be changed
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@@ -1656,6 +1656,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
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bad_fork_cancel_cgroup:
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cgroup_cancel_fork(p);
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bad_fork_free_pid:
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+ threadgroup_change_end(current);
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if (pid != &init_struct_pid)
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free_pid(pid);
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bad_fork_cleanup_thread:
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@@ -1688,7 +1689,6 @@ bad_fork_cleanup_policy:
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mpol_put(p->mempolicy);
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bad_fork_cleanup_threadgroup_lock:
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#endif
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- threadgroup_change_end(current);
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delayacct_tsk_free(p);
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bad_fork_cleanup_count:
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atomic_dec(&p->cred->user->processes);
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--
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2.7.4
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@ -642,6 +642,9 @@ Patch859: rc-core-fix-repeat-events.patch
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#rhbz 1371237
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Patch860: 0001-SUNRPC-Fix-infinite-looping-in-rpc_clnt_iterate_for_.patch
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# https://lkml.org/lkml/2016/8/30/566
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Patch861: 0001-cgroup-reduce-read-locked-section-of-cgroup_threadgr.patch
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# END OF PATCH DEFINITIONS
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%endif
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@ -2164,6 +2167,9 @@ fi
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#
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#
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%changelog
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* Fri Sep 02 2016 <labbott@fedoraproject.org>
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- Add fix for known cgroup deadlock
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* Mon Aug 29 2016 Laura Abbott <labbott@fedoraproject.org>
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- Add event decoding fix (rhbz 1360688)
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- Add fix for NFS client issue (rhbz 1371237)
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