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authorLinus Torvalds <torvalds@linux-foundation.org>2010-02-01 19:44:36 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2010-02-01 19:44:36 +0100
commit8ea85c2817301adb986b3b86dc20414595b776be (patch)
treed918bd0c2427a4e907475271863f88530eef4bf1 /kernel
parentMerge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/k... (diff)
parentsched: Correct printk whitespace in warning from cpu down task check (diff)
downloadlinux-8ea85c2817301adb986b3b86dc20414595b776be.tar.xz
linux-8ea85c2817301adb986b3b86dc20414595b776be.zip
Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: sched: Correct printk whitespace in warning from cpu down task check sched: Fix incorrect sanity check sched: Fix fork vs hotplug vs cpuset namespaces
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cpu.c10
-rw-r--r--kernel/fork.c15
-rw-r--r--kernel/sched.c39
3 files changed, 32 insertions, 32 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 1c8ddd6ee940..677f25376a38 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -151,13 +151,13 @@ static inline void check_for_tasks(int cpu)
write_lock_irq(&tasklist_lock);
for_each_process(p) {
- if (task_cpu(p) == cpu &&
+ if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
(!cputime_eq(p->utime, cputime_zero) ||
!cputime_eq(p->stime, cputime_zero)))
- printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
- (state = %ld, flags = %x) \n",
- p->comm, task_pid_nr(p), cpu,
- p->state, p->flags);
+ printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
+ "(state = %ld, flags = %x)\n",
+ p->comm, task_pid_nr(p), cpu,
+ p->state, p->flags);
}
write_unlock_irq(&tasklist_lock);
}
diff --git a/kernel/fork.c b/kernel/fork.c
index 5b2959b3ffc2..f88bd984df35 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1241,21 +1241,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
/* Need tasklist lock for parent etc handling! */
write_lock_irq(&tasklist_lock);
- /*
- * The task hasn't been attached yet, so its cpus_allowed mask will
- * not be changed, nor will its assigned CPU.
- *
- * The cpus_allowed mask of the parent may have changed after it was
- * copied first time - so re-copy it here, then check the child's CPU
- * to ensure it is on a valid CPU (and if not, just force it back to
- * parent's CPU). This avoids alot of nasty races.
- */
- p->cpus_allowed = current->cpus_allowed;
- p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
- if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
- !cpu_online(task_cpu(p))))
- set_task_cpu(p, smp_processor_id());
-
/* CLONE_PARENT re-uses the old parent */
if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
p->real_parent = current->real_parent;
diff --git a/kernel/sched.c b/kernel/sched.c
index 4508fe7048be..3a8fb30a91b1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2320,14 +2320,12 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
}
/*
- * Called from:
+ * Gets called from 3 sites (exec, fork, wakeup), since it is called without
+ * holding rq->lock we need to ensure ->cpus_allowed is stable, this is done
+ * by:
*
- * - fork, @p is stable because it isn't on the tasklist yet
- *
- * - exec, @p is unstable, retry loop
- *
- * - wake-up, we serialize ->cpus_allowed against TASK_WAKING so
- * we should be good.
+ * exec: is unstable, retry loop
+ * fork & wake-up: serialize ->cpus_allowed against TASK_WAKING
*/
static inline
int select_task_rq(struct task_struct *p, int sd_flags, int wake_flags)
@@ -2620,9 +2618,6 @@ void sched_fork(struct task_struct *p, int clone_flags)
if (p->sched_class->task_fork)
p->sched_class->task_fork(p);
-#ifdef CONFIG_SMP
- cpu = select_task_rq(p, SD_BALANCE_FORK, 0);
-#endif
set_task_cpu(p, cpu);
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
@@ -2652,6 +2647,21 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
{
unsigned long flags;
struct rq *rq;
+ int cpu = get_cpu();
+
+#ifdef CONFIG_SMP
+ /*
+ * Fork balancing, do it here and not earlier because:
+ * - cpus_allowed can change in the fork path
+ * - any previously selected cpu might disappear through hotplug
+ *
+ * We still have TASK_WAKING but PF_STARTING is gone now, meaning
+ * ->cpus_allowed is stable, we have preemption disabled, meaning
+ * cpu_online_mask is stable.
+ */
+ cpu = select_task_rq(p, SD_BALANCE_FORK, 0);
+ set_task_cpu(p, cpu);
+#endif
rq = task_rq_lock(p, &flags);
BUG_ON(p->state != TASK_WAKING);
@@ -2665,6 +2675,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
p->sched_class->task_woken(rq, p);
#endif
task_rq_unlock(rq, &flags);
+ put_cpu();
}
#ifdef CONFIG_PREEMPT_NOTIFIERS
@@ -7139,14 +7150,18 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
* the ->cpus_allowed mask from under waking tasks, which would be
* possible when we change rq->lock in ttwu(), so synchronize against
* TASK_WAKING to avoid that.
+ *
+ * Make an exception for freshly cloned tasks, since cpuset namespaces
+ * might move the task about, we have to validate the target in
+ * wake_up_new_task() anyway since the cpu might have gone away.
*/
again:
- while (p->state == TASK_WAKING)
+ while (p->state == TASK_WAKING && !(p->flags & PF_STARTING))
cpu_relax();
rq = task_rq_lock(p, &flags);
- if (p->state == TASK_WAKING) {
+ if (p->state == TASK_WAKING && !(p->flags & PF_STARTING)) {
task_rq_unlock(rq, &flags);
goto again;
}