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 <[email protected]> Fixes: 76f969e8948d ("cgroup: cgroup v2 freezer") Cc: [email protected] # v5.2+ Signed-off-by: Oleg Nesterov <[email protected]> --- kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/signal.c b/kernel/signal.c index 534fec2..f8eed86 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 { -- 2.5.0
