Michael Kerrisk wrote:
>
> Following up (belatedly) from my earlier message, I took Daniel
> Jacobowitz's suggestion to investigate the result from booting
> with "profile=2". When running my program (shwon below) on
> 2.6.14-rc4 to create 100 threads, and sending a core dump signal,
> the program takes 90 seconds to terminate, and readprofile shows
> the following:
I think the coredumping code in __group_complete_signal() is bogus
and what happens is:
group_send_sig_info(P, SIGQUIT):
adds SIGQUIT to ->shared_pending
__group_complete_signal:
->signal->group_exit_task = P;
for_each_thread(t) {
P->signal->group_stop_count ++;
// sets TIF_SIGPENDING
signal_wake_up(t)
}
Now, P receives the signal:
get_signal_to_deliver:
if (->signal->group_stop_count > 0) // YES
handle_group_stop():
if (->signal->group_exit_task == current) { // YES
->signal->group_exit_task = NULL
return 0;
}
signr = dequeue_signal(); // SIGQUIT
do_coredump:
->signal->flags = SIGNAL_GROUP_EXIT;
coredump_wait:
yield();
Now all other threads do:
get_signal_to_deliver:
if (->signal->group_stop_count > 0) // YES
handle_group_stop();
if (->signal->flags & SIGNAL_GROUP_EXIT) // YES
return 0;
signr = dequeue_signal(); // no pending signals
// recalc_sigpending_tsk() DOES NOT clear TIF_SIGPENDING,
// because it sees ->group_stop_count != 0.
return 0;
TIF_SIGPENDING is not cleared, so get_signal_to_deliver() will be
called again on return to userspace. When all threads will eat their
->time_slice, P will return from yield() and kill all threads.
Could you try this patch (added to mm tree):
http://marc.theaimsgroup.com/?l=linux-kernel&m=112887453531139
? It does not solve the whole problem, but may help.
Please report the result, if possible.
Oleg.
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