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authorDarren Hart <dvhart@linux.intel.com>2011-02-17 15:37:07 -0800
committerIngo Molnar <mingo@elte.hu>2011-03-04 11:14:30 +0100
commitc02aa73b1d18e43cfd79c2f193b225e84ca497c8 (patch)
treebd36bf363e667a915e3ceda99221531362139d51 /kernel/sched.c
parenta2f5c9ab79f78e8b91ac993e0543d65b661dd19b (diff)
downloadop-kernel-dev-c02aa73b1d18e43cfd79c2f193b225e84ca497c8.zip
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sched: Allow users with sufficient RLIMIT_NICE to change from SCHED_IDLE policy
The current scheduler implementation returns -EPERM when trying to change from SCHED_IDLE to SCHED_OTHER or SCHED_BATCH. Since SCHED_IDLE is considered to be a nice 20 on steroids, changing to another policy should be allowed provided the RLIMIT_NICE is accounted for. This patch allows the following test-case to pass with RLIMIT_NICE=40, but still fail with RLIMIT_NICE=10 when the calling process is run from a typical shell (nice 0, or 20 in rlimit terms). int main() { int ret; struct sched_param sp; sp.sched_priority = 0; /* switch to SCHED_IDLE */ ret = sched_setscheduler(0, SCHED_IDLE, &sp); printf("setscheduler IDLE: %d\n", ret); if (ret) return ret; /* switch back to SCHED_OTHER */ ret = sched_setscheduler(0, SCHED_OTHER, &sp); printf("setscheduler OTHER: %d\n", ret); return ret; } $ ulimit -e 40 $ ./test setscheduler IDLE: 0 setscheduler OTHER: 0 $ ulimit -e 10 $ ulimit -e 10 $ ./test setscheduler IDLE: 0 setscheduler OTHER: -1 Signed-off-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Richard Purdie <richard.purdie@linuxfoundation.org> LKML-Reference: <4D657BEE.4040608@linux.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 0c87126..f303070 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4981,12 +4981,15 @@ recheck:
param->sched_priority > rlim_rtprio)
return -EPERM;
}
+
/*
- * Like positive nice levels, dont allow tasks to
- * move out of SCHED_IDLE either:
+ * Treat SCHED_IDLE as nice 20. Only allow a switch to
+ * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
*/
- if (p->policy == SCHED_IDLE && policy != SCHED_IDLE)
- return -EPERM;
+ if (p->policy == SCHED_IDLE && policy != SCHED_IDLE) {
+ if (!can_nice(p, TASK_NICE(p)))
+ return -EPERM;
+ }
/* can't change other user's priorities */
if (!check_same_owner(p))
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