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authorOleg Nesterov <oleg@tv-sign.ru>2006-09-29 02:00:48 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-29 09:18:17 -0700
commit5fe1d75f34974046fffcca5e22fb8a7b42fded33 (patch)
tree831e360aa8d7d37c7c5202937a2f617ebea6e737
parentc9472e0f28cd2f0695a0ac3a0b4bd33f21714a7e (diff)
[PATCH] do_sched_setscheduler(): don't take tasklist_lock
Use rcu locks instead. sched_setscheduler() now takes ->siglock before reading ->signal->rlim[]. 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.c28
1 files changed, 18 insertions, 10 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index b946209d9c1..f9b3c6a414f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4080,6 +4080,8 @@ static void __setscheduler(struct task_struct *p, int policy, int prio)
* @p: the task in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
+ *
+ * NOTE: the task may be already dead
*/
int sched_setscheduler(struct task_struct *p, int policy,
struct sched_param *param)
@@ -4115,19 +4117,26 @@ 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);
+
/*
* 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)) &&
- !p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
+ !rlim_rtprio)
return -EPERM;
/* can't increase priority */
if ((policy != SCHED_NORMAL && policy != SCHED_BATCH) &&
param->sched_priority > p->rt_priority &&
- param->sched_priority >
- p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
+ param->sched_priority > rlim_rtprio)
return -EPERM;
/* can't change other user's priorities */
if ((current->euid != p->euid) &&
@@ -4193,14 +4202,13 @@ do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
return -EINVAL;
if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
return -EFAULT;
- read_lock_irq(&tasklist_lock);
+
+ rcu_read_lock();
+ retval = -ESRCH;
p = find_process_by_pid(pid);
- if (!p) {
- read_unlock_irq(&tasklist_lock);
- return -ESRCH;
- }
- retval = sched_setscheduler(p, policy, &lparam);
- read_unlock_irq(&tasklist_lock);
+ if (p != NULL)
+ retval = sched_setscheduler(p, policy, &lparam);
+ rcu_read_unlock();
return retval;
}