On 03/19, Roland McGrath wrote:
>
> I'm no scheduler expert and I don't know whether the exact placement in
> your change is the optimal one.
Agreed, can't we do a bit more simple patch?
--- kernel/signal.c
+++ kernel/signal.c
@@ -1572,8 +1572,10 @@ static void ptrace_stop(int exit_code, i
spin_unlock_irq(¤t->sighand->siglock);
read_lock(&tasklist_lock);
if (may_ptrace_stop()) {
+ preempt_disable();
do_notify_parent_cldstop(current, CLD_TRAPPED);
read_unlock(&tasklist_lock);
+ preempt_enable_no_resched();
schedule();
} else {
/*
Yes, the task can be preempted right after spin_unlock(->siglock), but
this is unlikely. We need the "synchronous" wakeup, and this patch helps
as well.
Actually, I don't know which ptrace requests really need to make sure
the tracee was deactivated. Perhaps they can call wait_task_inactive()
themselves? I guess this is bad idea, but most of requests definitely
do not need wait_task_inactive().
Oleg.
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