The patch titled
do_wait() wakeup optimization: child_wait_callback: check __WNOTHREAD case
has been added to the -mm tree. Its filename is
do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case.patch
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------------------------------------------------------
Subject: do_wait() wakeup optimization: child_wait_callback: check __WNOTHREAD case
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Suggested by Roland.
do_wait(__WNOTHREAD) can only succeed if the caller is either ptracer, or
it is ->real_parent and the child is not traced. IOW, caller == p->parent
otherwise we should not wake up.
Change child_wait_callback() to check this. Ratan reports the workload with
CPU load >99% caused by unnecessary wakeups, should be fixed by this patch.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Roland McGrath <roland@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Ratan Nalumasu <rnalumasu@xxxxxxxxx>
Cc: Vitaly Mayatskikh <vmayatsk@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 3 +++
1 file changed, 3 insertions(+)
diff -puN kernel/exit.c~do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case kernel/exit.c
--- a/kernel/exit.c~do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case
+++ a/kernel/exit.c
@@ -1577,6 +1577,9 @@ static int child_wait_callback(wait_queu
if (!eligible_child(wo, p))
return 0;
+ if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
+ return 0;
+
return default_wake_function(wait, mode, sync, key);
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
linux-next.patch
cred_guard_mutex-do-not-return-eintr-to-user-space.patch
rework-fix-is_single_threaded.patch
getrusage-fill-ru_maxrss-value.patch
getrusage-fill-ru_maxrss-value-update.patch
ptrace-__ptrace_detach-do-__wake_up_parent-if-we-reap-the-tracee.patch
do_wait-wakeup-optimization-shift-security_task_wait-from-eligible_child-to-wait_consider_task.patch
do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup.patch
do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case.patch
signals-tracehook_notify_jctl-change.patch
utrace-core.patch
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