The patch titled
do_sched_setscheduler(): don't take tasklist_lock
has been added to the -mm tree. Its filename is
do_sched_setscheduler-dont-take-tasklist_lock.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: do_sched_setscheduler(): don't take tasklist_lock
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Use rcu locks instead. sched_setscheduler() now takes ->siglock
before reading ->signal->rlim[].
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/sched.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)
diff -puN kernel/sched.c~do_sched_setscheduler-dont-take-tasklist_lock kernel/sched.c
--- a/kernel/sched.c~do_sched_setscheduler-dont-take-tasklist_lock
+++ a/kernel/sched.c
@@ -4043,6 +4043,8 @@ static void __setscheduler(struct task_s
* @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)
@@ -4078,19 +4080,26 @@ 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) &&
@@ -4156,14 +4165,13 @@ do_sched_setscheduler(pid_t pid, int pol
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;
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
sys_getppid-oopses-on-debug-kernel-v2.patch
for-2618-revert-drop-tasklist-lock-in-do_sched_setscheduler.patch
pid-implement-transfer_pid-and-use-it-to-simplify-de_thread.patch
pid-remove-temporary-debug-code-in-attach_pid.patch
rtmutex-clean-up-and-remove-some-extra-spinlocks.patch
rtmutex-clean-up-and-remove-some-extra-spinlocks-more.patch
elf_core_dump-dont-take-tasklist_lock.patch
elf_fdpic_core_dump-dont-take-tasklist_lock.patch
has_stopped_jobs-cleanup.patch
__dequeue_signal-cleanup.patch
do_sched_setscheduler-dont-take-tasklist_lock.patch
introduce-is_rt_policy-helper.patch
simplify-pid-iterators.patch
pidhash-temporary-debug-checks.patch
-
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