diff options
| author | Darren Hart <dvhart@linux.intel.com> | 2011-02-17 15:37:07 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-03-04 11:14:30 +0100 |
| commit | c02aa73b1d18e43cfd79c2f193b225e84ca497c8 (patch) | |
| tree | bd36bf363e667a915e3ceda99221531362139d51 /kernel/sched.c | |
| parent | a2f5c9ab79f78e8b91ac993e0543d65b661dd19b (diff) | |
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.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 0c8712630f0..f3030709d82 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)) |