From 5c01ba49e6647d86bc7576105f82027200d1f303 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 23 Sep 2009 15:56:48 -0700 Subject: [PATCH] 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 Tested-by: KAMEZAWA Hiroyuki Signed-off-by: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 270a68b7f22f..3fb9a77863d5 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1111,13 +1111,16 @@ static struct pid *task_pid_type(struct task_struct *task, enum pid_type type) return pid; } +static inline int eligible_pid(struct wait_opts *wo, struct task_struct *p) +{ + return wo->wo_type == PIDTYPE_MAX || + task_pid_type(p, wo->wo_type) == wo->wo_pid; +} + static int eligible_child(struct wait_opts *wo, struct task_struct *p) { - if (wo->wo_type < PIDTYPE_MAX) { - if (task_pid_type(p, wo->wo_type) != wo->wo_pid) - return 0; - } - + if (!eligible_pid(wo, p)) + return 0; /* Wait for all children (clone and not) if __WALL is set; * otherwise, wait for clone children *only* if __WCLONE is * set; otherwise, wait for non-clone children *only*. (Note: @@ -1578,7 +1581,7 @@ static int child_wait_callback(wait_queue_t *wait, unsigned mode, child_wait); struct task_struct *p = key; - if (!eligible_child(wo, p)) + if (!eligible_pid(wo, p)) return 0; if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)