do_wait-wakeup-optimization: fix child_wait_callback()->eligible_child() usage
child_wait_callback()->eligible_child() is not right, we can miss the wakeup if the task was detached before __wake_up_parent() and the caller of do_wait() didn't use __WALL. Move ->wo_pid checks from eligible_child() to the new helper, eligible_pid(), and change child_wait_callback() to use it instead of eligible_child(). Note: actually I think it would be better to fix the __WCLONE check in eligible_child(), it doesn't look exactly right. But it is not clear what is the supposed behaviour, and any change is user-visible. Reported-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Tested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> 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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@ -1111,13 +1111,16 @@ static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
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return pid;
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}
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static inline int eligible_pid(struct wait_opts *wo, struct task_struct *p)
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{
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return wo->wo_type == PIDTYPE_MAX ||
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task_pid_type(p, wo->wo_type) == wo->wo_pid;
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}
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static int eligible_child(struct wait_opts *wo, struct task_struct *p)
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{
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if (wo->wo_type < PIDTYPE_MAX) {
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if (task_pid_type(p, wo->wo_type) != wo->wo_pid)
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return 0;
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}
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if (!eligible_pid(wo, p))
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return 0;
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/* Wait for all children (clone and not) if __WALL is set;
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* otherwise, wait for clone children *only* if __WCLONE is
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* set; otherwise, wait for non-clone children *only*. (Note:
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@ -1578,7 +1581,7 @@ static int child_wait_callback(wait_queue_t *wait, unsigned mode,
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child_wait);
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struct task_struct *p = key;
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if (!eligible_child(wo, p))
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if (!eligible_pid(wo, p))
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return 0;
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if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
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