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UPSTREAM: cgroup: freezer: call cgroup_enter_frozen() with preemption disabled in ptrace_stop()

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ptrace_stop() does preempt_enable_no_resched() to avoid the preemption,
but after that cgroup_enter_frozen() does spin_lock/unlock and this adds
another preemption point.

Reported-and-tested-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Fixes: 76f969e8948d ("cgroup: cgroup v2 freezer")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Change-Id: Ic53e0f2d6624b0bb90817b0c57060fb7db971348
(cherry picked from commit 937c6b27c73e02cd4114f95f5c37ba2c29fadba1)
Bug: 154548692
Signed-off-by: Marco Ballesio <balejs@google.com>
This commit is contained in:
Oleg Nesterov 2019-10-09 17:02:30 +02:00 committed by Marco Ballesio
parent fe5770aeda
commit caf7caca0b
1 changed files with 1 additions and 1 deletions
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2
kernel/signal.c
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@ -2131,8 +2131,8 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
*/ */
preempt_disable(); preempt_disable();
read_unlock(&tasklist_lock); read_unlock(&tasklist_lock);
preempt_enable_no_resched();
cgroup_enter_frozen(); cgroup_enter_frozen();
preempt_enable_no_resched();
freezable_schedule(); freezable_schedule();
cgroup_leave_frozen(true); cgroup_leave_frozen(true);
} else { } else {