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authorOleg Nesterov <oleg@redhat.com>2009-09-23 15:56:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-24 07:21:00 -0700
commit5c01ba49e6647d86bc7576105f82027200d1f303 (patch)
tree700aa5dbda7c726e8b60803225587a1bc4fdbdb5
parentb4fe51823d797d6959b2eee7868023e61606daa9 (diff)
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>
-rw-r--r--kernel/exit.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 270a68b7f22..3fb9a77863d 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 int eligible_child(struct wait_opts *wo, struct task_struct *p)
+static inline int eligible_pid(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;
- }
+ 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 (!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)