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authorOleg Nesterov <oleg@tv-sign.ru>2006-09-29 02:00:50 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-29 09:18:17 -0700
commit8dc3e9099e01dfdd53f27f329c268eced03dfef6 (patch)
treec4a88aeabd5726185bf65c75cc52145d9dc33e43
parent57a6f51c4281aa3119975473c70dce0480d322bd (diff)
[PATCH] sched_setscheduler: fix? policy checks
I am not sure this patch is correct: I can't understand what the current code does, and I don't know what it was supposed to do. The comment says: * can't change policy, except between SCHED_NORMAL * and SCHED_BATCH: The code: if (((policy != SCHED_NORMAL && p->policy != SCHED_BATCH) && (policy != SCHED_BATCH && p->policy != SCHED_NORMAL)) && But this is equivalent to: if ( (is_rt_policy(policy) && has_rt_policy(p)) && which means something different. We can't _decrease_ the current ->rt_priority with such a check (if rlim[RLIMIT_RTPRIO] == 0). Probably, it was supposed to be: if ( !(policy == SCHED_NORMAL && p->policy == SCHED_BATCH) && !(policy == SCHED_BATCH && p->policy == SCHED_NORMAL) this matches the comment, but strange: it doesn't allow to _drop_ the realtime priority when rlim[RLIMIT_RTPRIO] == 0. I think the right check would be: /* can't set/change rt policy */ if (is_rt_policy(policy) && policy != p->policy && !rlim_rtprio) return -EPERM; Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--kernel/sched.c38
1 files changed, 18 insertions, 20 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index c3c718aea618..155a33da7aa7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4116,27 +4116,25 @@ recheck:
* Allow unprivileged RT tasks to decrease priority:
*/
if (!capable(CAP_SYS_NICE)) {
- unsigned long rlim_rtprio;
- unsigned long flags;
-
- if (!lock_task_sighand(p, &flags))
- return -ESRCH;
- rlim_rtprio = p->signal->rlim[RLIMIT_RTPRIO].rlim_cur;
- unlock_task_sighand(p, &flags);
+ if (is_rt_policy(policy)) {
+ unsigned long rlim_rtprio;
+ unsigned long flags;
+
+ if (!lock_task_sighand(p, &flags))
+ return -ESRCH;
+ rlim_rtprio = p->signal->rlim[RLIMIT_RTPRIO].rlim_cur;
+ unlock_task_sighand(p, &flags);
+
+ /* can't set/change the rt policy */
+ if (policy != p->policy && !rlim_rtprio)
+ return -EPERM;
+
+ /* can't increase priority */
+ if (param->sched_priority > p->rt_priority &&
+ param->sched_priority > rlim_rtprio)
+ return -EPERM;
+ }
- /*
- * can't change policy, except between SCHED_NORMAL
- * and SCHED_BATCH:
- */
- if (((policy != SCHED_NORMAL && p->policy != SCHED_BATCH) &&
- (policy != SCHED_BATCH && p->policy != SCHED_NORMAL)) &&
- !rlim_rtprio)
- return -EPERM;
- /* can't increase priority */
- if (is_rt_policy(policy) &&
- param->sched_priority > p->rt_priority &&
- param->sched_priority > rlim_rtprio)
- return -EPERM;
/* can't change other user's priorities */
if ((current->euid != p->euid) &&
(current->euid != p->uid))