[GIT PULL] cgroup fixes for v5.4-rc7

[Tejun Heo]

Hello, Linus.

Sorry, I sat on this for too long.

There's an inadvertent preemption point in ptrace_stop() which was
reliably triggering for a test scenario significantly slowing it down.
This pull request contains Oleg's fix to remove the unwanted
preemption point.

Thanks.

The following changes since commit 9e208aa06c2109b45eec6be049a8e47034748c20:

  Merge tag 'xfs-5.4-fixes-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux (2019-10-10 11:47:16 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-5.4-fixes

for you to fetch changes up to 937c6b27c73e02cd4114f95f5c37ba2c29fadba1:

  cgroup: freezer: call cgroup_enter_frozen() with preemption disabled in ptrace_stop() (2019-10-11 08:39:57 -0700)

----------------------------------------------------------------
Oleg Nesterov (1):
      cgroup: freezer: call cgroup_enter_frozen() with preemption disabled in ptrace_stop()

 kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index c4da1ef56fdf..bcd46f547db3 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2205,8 +2205,8 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 		 */
 		preempt_disable();
 		read_unlock(&tasklist_lock);
-		preempt_enable_no_resched();
 		cgroup_enter_frozen();
+		preempt_enable_no_resched();
 		freezable_schedule();
 		cgroup_leave_frozen(true);
 	} else {

-- 
tejun