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Groups > linux.kernel > #1375984

[PATCH 3.12 14/98] sched: Fix race between task_group and sched_task_group

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From: Kirill Tkhai <ktkhai@parallels.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit eeb61e53ea19be0c4015b00b2e8b3b2185436f2b upstream.

The race may happen when somebody is changing task_group of a forking task.
Child's cgroup is the same as parent's after dup_task_struct() (there just
memory copying). Also, cfs_rq and rt_rq are the same as parent's.

But if parent changes its task_group before it's called cgroup_post_fork(),
we do not reflect this situation on child. Child's cfs_rq and rt_rq remain
the same, while child's task_group changes in cgroup_post_fork().

To fix this we introduce fork() method, which calls sched_move_task() directly.
This function changes sched_task_group on appropriate (also its logic has
no problem with freshly created tasks, so we shouldn't introduce something
special; we are able just to use it).

Possibly, this decides the Burke Libbey's problem: https://lkml.org/lkml/2014/10/24/456

Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1414405105.19914.169.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 kernel/sched/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3800316d7424..7381119ec1e9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7233,6 +7233,11 @@ static void cpu_cgroup_css_offline(struct cgroup_subsys_state *css)
 	sched_offline_group(tg);
 }
 
+static void cpu_cgroup_fork(struct task_struct *task)
+{
+	sched_move_task(task);
+}
+
 static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css,
 				 struct cgroup_taskset *tset)
 {
@@ -7602,6 +7607,7 @@ struct cgroup_subsys cpu_cgroup_subsys = {
 	.css_free	= cpu_cgroup_css_free,
 	.css_online	= cpu_cgroup_css_online,
 	.css_offline	= cpu_cgroup_css_offline,
+	.fork		= cpu_cgroup_fork,
 	.can_attach	= cpu_cgroup_can_attach,
 	.attach		= cpu_cgroup_attach,
 	.exit		= cpu_cgroup_exit,
-- 
2.8.1

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[PATCH 3.12 00/98] 3.12.58-stable review Jiri Slaby <jslaby@suse.cz> - 2016-04-11 15:30 +0200
  Re: [PATCH 3.12 00/98] 3.12.58-stable review Guenter Roeck <linux@roeck-us.net> - 2016-04-11 15:40 +0200
    Re: [PATCH 3.12 00/98] 3.12.58-stable review Jiri Slaby <jslaby@suse.cz> - 2016-04-14 10:30 +0200
  [PATCH 3.12 01/98] ipr: Fix out-of-bounds null overwrite Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 18/98] ALSA: rawmidi: Make snd_rawmidi_transmit() race-free Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 23/98] KVM: SVM: add rdmsr support for AMD event registers Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 08/98] xen-netback: use RING_COPY_REQUEST() throughout Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 07/98] xen-netback: don't use last request to determine minimum Tx credit Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 03/98] ipv4: Don't do expensive useless work during inetdev destroy. Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 27/98] perf, nmi: Fix unknown NMI warning Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 14/98] sched: Fix race between task_group and sched_task_group Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 20/98] memcg: do not hang on OOM when killed by userspace OOM access to memory reserves Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 19/98] ALSA: seq: Fix leak of pool buffer at concurrent writes Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 09/98] xen-blkback: only read request operation from shared ring once Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 05/98] kernel: Provide READ_ONCE and ASSIGN_ONCE Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
      Re: [PATCH 3.12 05/98] kernel: Provide READ_ONCE and ASSIGN_ONCE Christian Borntraeger <borntraeger@de.ibm.com> - 2016-04-11 16:20 +0200
    [PATCH 3.12 06/98] xen: Add RING_COPY_REQUEST() Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 17/98] drivers/base/memory.c: fix kernel warning during memory hotplug on ppc64 Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 04/98] umount: Do not allow unmounting rootfs. Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 10/98] xen-blkback: read from indirect descriptors only once Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 02/98] ipr: Fix regression when loading firmware Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 15/98] Btrfs: skip locking when searching commit root Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
  Re: [PATCH 3.12 00/98] 3.12.58-stable review shuahkh <shuahkh@osg.sisa.samsung.com> - 2016-04-11 19:30 +0200

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