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| author | Oleg Nesterov <oleg@redhat.com> | 2009-09-23 15:56:48 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-09-24 07:21:00 -0700 |
| commit | 5c01ba49e6647d86bc7576105f82027200d1f303 (patch) | |
| tree | 700aa5dbda7c726e8b60803225587a1bc4fdbdb5 /kernel | |
| parent | b4fe51823d797d6959b2eee7868023e61606daa9 (diff) | |
| download | lwn-5c01ba49e6647d86bc7576105f82027200d1f303.tar.gz lwn-5c01ba49e6647d86bc7576105f82027200d1f303.zip | |
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>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/exit.c | 15 |
1 files 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 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) |