signals: document CLD_CONTINUED notification mechanics
A couple of small comments about how CLD_CONTINUED notification works. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -633,6 +633,11 @@ static int prepare_signal(int sig, struct task_struct *p)
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why |= SIGNAL_CLD_STOPPED;
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if (why) {
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/*
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* The first thread which returns from finish_stop()
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* will take ->siglock, notice SIGNAL_CLD_MASK, and
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* notify its parent. See get_signal_to_deliver().
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*/
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signal->flags = why | SIGNAL_STOP_CONTINUED;
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signal->group_stop_count = 0;
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signal->group_exit_code = 0;
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@ -1694,7 +1699,11 @@ relock:
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try_to_freeze();
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spin_lock_irq(&sighand->siglock);
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/*
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* Every stopped thread goes here after wakeup. Check to see if
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* we should notify the parent, prepare_signal(SIGCONT) encodes
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* the CLD_ si_code into SIGNAL_CLD_MASK bits.
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*/
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if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
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int why = (signal->flags & SIGNAL_STOP_CONTINUED)
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? CLD_CONTINUED : CLD_STOPPED;
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