Messages in this thread Patch in this message | | | Date | Tue, 1 Sep 2009 14:23:25 +0200 | From | Oleg Nesterov <> | Subject | [PATCH -mm 1/2] do_wait-wakeup-optimization: fix child_wait_callback()->eligible_child() usage |
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(on top of do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case.patch, fixes do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup.patch)
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> Signed-off-by: Oleg Nesterov <oleg@redhat.com> ---
kernel/exit.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)
--- WAIT/kernel/exit.c~2_WAKE_PARENT_ELIGIBLE_FIX 2009-09-01 12:49:27.000000000 +0200 +++ WAIT/kernel/exit.c 2009-09-01 12:59:23.000000000 +0200 @@ -1106,13 +1106,16 @@ static struct pid *task_pid_type(struct 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: @@ -1564,7 +1567,7 @@ static int child_wait_callback(wait_queu 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)
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