[tip:sched/urgent] sched: Fix odd values in effective_load() calculations

tip-bot for Yuyang Du
2015-01-09T12:34:12Z

Commit-ID: 32a8df4e0b33fccc9715213b382160415b5c4008
Gitweb: http://git.kernel.org/tip/32a8df4e0b33fccc9715213b382160415b5c4008
Author: Yuyang Du <yuyang.du@intel.com>
AuthorDate: Fri, 19 Dec 2014 08:29:56 +0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 9 Jan 2015 11:18:54 +0100

sched: Fix odd values in effective_load() calculations

In effective_load, we have (long w * unsigned long tg->shares) / long W,
when w is negative, it is cast to unsigned long and hence the product is
insanely large. Fix this by casting tg->shares to long.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141219002956.GA25405@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index df2cdf7..6b99659 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4424,7 +4424,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
* wl = S * s'_i; see (2)
*/
if (W > 0 && w < W)
- wl = (w * tg->shares) / W;
+ wl = (w * (long)tg->shares) / W;
else
wl = tg->shares;