__group_complete_signal(): fix coredump with group stop race
When __group_complete_signal() sees sig_kernel_coredump() signal, it starts the group stop, but sets ->group_exit_task = t in a hope that "t" will actually dequeue this signal and invoke do_coredump(). However, by the time "t" enters get_signal_to_deliver() it is possible that the signal was blocked/ignored or we have another pending !SIG_KERNEL_COREDUMP_MASK signal which will be dequeued first. This means the task could be stopped but not killed. Remove this code from __group_complete_signal(). Note also this patch removes the bogus signal_wake_up(t, 1). This thread can't be STOPPED/TRACED, note the corresponding check in wants_signal(). Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Robin Holt <holt@sgi.com> Cc: Roland McGrath <roland@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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