From ab2789213d224202237292d78aaa0c386c7b28b2 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 15 Dec 2011 11:47:00 -0800
Subject: [PATCH] sched: Fix select_idle_sibling() regression in selecting an
idle SMT sibling
Mike Galbraith reported that this recent commit:
commit 4dcfe1025b513c2c1da5bf5586adb0e80148f612
Author: Peter Zijlstra <peterz@infradead.org>
Date: Thu Nov 10 13:01:10 2011 +0100
sched: Avoid SMT siblings in select_idle_sibling() if possible
stopped selecting an idle SMT sibling when there are no idle
cores in a single socket system.
Intent of the select_idle_sibling() was to fallback to an idle
SMT sibling, if it fails to identify an idle core. But this
fallback was not happening on systems where all the scheduler
domains had `SD_SHARE_PKG_RESOURCES' flag set.
Fix it. Slightly bigger patch of cleaning all these goto's etc
is queued up for the next release.
Reported-by: Mike Galbraith <efault@gmx.de>
Reported-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1323978421.1984.244.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched_fair.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a78ed2736ba79..8a39fa3e3c6c7 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2352,13 +2352,11 @@ again:
if (!smt && (sd->flags & SD_SHARE_CPUPOWER))
continue;
- if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) {
- if (!smt) {
- smt = 1;
- goto again;
- }
+ if (smt && !(sd->flags & SD_SHARE_CPUPOWER))
+ break;
+
+ if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
break;
- }
sg = sd->groups;
do {
@@ -2378,6 +2376,10 @@ next:
sg = sg->next;
} while (sg != sd->groups);
}
+ if (!smt) {
+ smt = 1;
+ goto again;
+ }
done:
rcu_read_unlock();
--
2.30.2