sched: group scheduler, set uid share fix

setting cpu share to 1 causes hangs, as reported in:

    http://bugzilla.kernel.org/show_bug.cgi?id=9779

as the default share is 1024, the values of 0 and 1 can indeed
cause problems. Limit it to 2 or higher values.

These values can only be set by the root user - but still it
makes sense to protect against nonsensical values.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 37cf07aa41647741e1581f8120b4cb2a291c5545..e76b11ca6df320648ae32eb122afa80fc4c4faca 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7153,6 +7153,14 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
 {
        int i;
 
+       /*
+        * A weight of 0 or 1 can cause arithmetics problems.
+        * (The default weight is 1024 - so there's no practical
+        *  limitation from this.)
+        */
+       if (shares < 2)
+               shares = 2;
+
        spin_lock(&tg->lock);
        if (tg->shares == shares)
                goto done;