From: Oleg Nesterov oleg@redhat.com
commit 937c6b27c73e02cd4114f95f5c37ba2c29fadba1 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/signal.c +++ b/kernel/signal.c @@ -2205,8 +2205,8 @@ static void ptrace_stop(int exit_code, i */ preempt_disable(); read_unlock(&tasklist_lock); - preempt_enable_no_resched(); cgroup_enter_frozen(); + preempt_enable_no_resched(); freezable_schedule(); cgroup_leave_frozen(true); } else {