Merge remote-tracking branch 'origin/f24' into f24-user-thl-vanilla-fedorakernel-4.7.2-201.vanilla.knurd.1.fc24

1 files changed, 112 insertions, 0 deletions

diff --git a/0001-cgroup-reduce-read-locked-section-of-cgroup_threadgr.patch b/0001-cgroup-reduce-read-locked-section-of-cgroup_threadgr.patch
new file mode 100644
index 000000000..daad25310
--- /dev/null
+++ b/0001-cgroup-reduce-read-locked-section-of-cgroup_threadgr.patch
@@ -0,0 +1,112 @@
+From 568ac888215c7fb2fabe8ea739b00ec3c1f5d440 Mon Sep 17 00:00:00 2001
+From: Balbir Singh <bsingharora@gmail.com>
+Date: Wed, 10 Aug 2016 15:43:06 -0400
+Subject: [PATCH] cgroup: reduce read locked section of
+ cgroup_threadgroup_rwsem during fork
+
+cgroup_threadgroup_rwsem is acquired in read mode during process exit
+and fork.  It is also grabbed in write mode during
+__cgroups_proc_write().  I've recently run into a scenario with lots
+of memory pressure and OOM and I am beginning to see
+
+systemd
+
+ __switch_to+0x1f8/0x350
+ __schedule+0x30c/0x990
+ schedule+0x48/0xc0
+ percpu_down_write+0x114/0x170
+ __cgroup_procs_write.isra.12+0xb8/0x3c0
+ cgroup_file_write+0x74/0x1a0
+ kernfs_fop_write+0x188/0x200
+ __vfs_write+0x6c/0xe0
+ vfs_write+0xc0/0x230
+ SyS_write+0x6c/0x110
+ system_call+0x38/0xb4
+
+This thread is waiting on the reader of cgroup_threadgroup_rwsem to
+exit.  The reader itself is under memory pressure and has gone into
+reclaim after fork. There are times the reader also ends up waiting on
+oom_lock as well.
+
+ __switch_to+0x1f8/0x350
+ __schedule+0x30c/0x990
+ schedule+0x48/0xc0
+ jbd2_log_wait_commit+0xd4/0x180
+ ext4_evict_inode+0x88/0x5c0
+ evict+0xf8/0x2a0
+ dispose_list+0x50/0x80
+ prune_icache_sb+0x6c/0x90
+ super_cache_scan+0x190/0x210
+ shrink_slab.part.15+0x22c/0x4c0
+ shrink_zone+0x288/0x3c0
+ do_try_to_free_pages+0x1dc/0x590
+ try_to_free_pages+0xdc/0x260
+ __alloc_pages_nodemask+0x72c/0xc90
+ alloc_pages_current+0xb4/0x1a0
+ page_table_alloc+0xc0/0x170
+ __pte_alloc+0x58/0x1f0
+ copy_page_range+0x4ec/0x950
+ copy_process.isra.5+0x15a0/0x1870
+ _do_fork+0xa8/0x4b0
+ ppc_clone+0x8/0xc
+
+In the meanwhile, all processes exiting/forking are blocked almost
+stalling the system.
+
+This patch moves the threadgroup_change_begin from before
+cgroup_fork() to just before cgroup_canfork().  There is no nee to
+worry about threadgroup changes till the task is actually added to the
+threadgroup.  This avoids having to call reclaim with
+cgroup_threadgroup_rwsem held.
+
+tj: Subject and description edits.
+
+Signed-off-by: Balbir Singh <bsingharora@gmail.com>
+Acked-by: Zefan Li <lizefan@huawei.com>
+Cc: Oleg Nesterov <oleg@redhat.com>
+Cc: Andrew Morton <akpm@linux-foundation.org>
+Cc: stable@vger.kernel.org # v4.2+
+Signed-off-by: Tejun Heo <tj@kernel.org>
+---
+ kernel/fork.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/kernel/fork.c b/kernel/fork.c
+index 52e725d..aaf7823 100644
+--- a/kernel/fork.c
++++ b/kernel/fork.c
+@@ -1404,7 +1404,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
+ 	p->real_start_time = ktime_get_boot_ns();
+ 	p->io_context = NULL;
+ 	p->audit_context = NULL;
+-	threadgroup_change_begin(current);
+ 	cgroup_fork(p);
+ #ifdef CONFIG_NUMA
+ 	p->mempolicy = mpol_dup(p->mempolicy);
+@@ -1556,6 +1555,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
+ 	INIT_LIST_HEAD(&p->thread_group);
+ 	p->task_works = NULL;
+ 
++	threadgroup_change_begin(current);
+ 	/*
+ 	 * Ensure that the cgroup subsystem policies allow the new process to be
+ 	 * forked. It should be noted the the new process's css_set can be changed
+@@ -1656,6 +1656,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
+ bad_fork_cancel_cgroup:
+ 	cgroup_cancel_fork(p);
+ bad_fork_free_pid:
++	threadgroup_change_end(current);
+ 	if (pid != &init_struct_pid)
+ 		free_pid(pid);
+ bad_fork_cleanup_thread:
+@@ -1688,7 +1689,6 @@ bad_fork_cleanup_policy:
+ 	mpol_put(p->mempolicy);
+ bad_fork_cleanup_threadgroup_lock:
+ #endif
+-	threadgroup_change_end(current);
+ 	delayacct_tsk_free(p);
+ bad_fork_cleanup_count:
+ 	atomic_dec(&p->cred->user->processes);
+-- 
+2.7.4
+