From ab2789213d224202237292d78aaa0c386c7b28b2 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra 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 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 Reported-by: Alex Shi Signed-off-by: Peter Zijlstra Signed-off-by: Suresh Siddha Link: http://lkml.kernel.org/r/1323978421.1984.244.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar --- 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 a78ed2736ba7..8a39fa3e3c6c 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();