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Date: Sun, 6 Dec 2015 10:52:52 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
cc: LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>
Subject: [GIT pull] scheduler fixes for 4.4
Linus,
please pull the latest sched-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus
This updates contains the following changes:
- Fix a signal handling regression in the bit wait functions.
- Avoid false positive warnings in the wakeup path.
- Initialize the scheduler root domain properly.
- Handle gtime calculations in proc/$PID/stat proper.
- Add more documentation for the barriers in try_to_wake_up().
- Fix a subtle race in try_to_wake_up() which might cause a task to
be scheduled on two cpus
- Compile static helper function only when it is used.
Thanks,
tglx
------------------>
Arnd Bergmann (1):
sched/rt: Hide the push_irq_work_func() declaration
Hiroshi Shimamoto (1):
sched/cputime: Fix invalid gtime in proc
Peter Zijlstra (3):
sched/wait: Fix signal handling in bit wait helpers
sched/core: Better document the try_to_wake_up() barriers
sched/core: Fix an SMP ordering race in try_to_wake_up() vs. schedule()
Sasha Levin (1):
sched/core: Remove false-positive warning from wake_up_process()
Xunlei Pang (1):
sched/core: Clear the root_domain cpumasks in init_rootdomain()
kernel/sched/core.c | 36 ++++++++++++++++++++++++++++++------
kernel/sched/cputime.c | 3 +++
kernel/sched/rt.c | 2 +-
kernel/sched/sched.h | 3 +++
kernel/sched/wait.c | 16 ++++++++--------
5 files changed, 45 insertions(+), 15 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4d568ac9319e..7063c6a07440 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1947,13 +1947,38 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
#ifdef CONFIG_SMP
/*
+ * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
+ * possible to, falsely, observe p->on_cpu == 0.
+ *
+ * One must be running (->on_cpu == 1) in order to remove oneself
+ * from the runqueue.
+ *
+ * [S] ->on_cpu = 1; [L] ->on_rq
+ * UNLOCK rq->lock
+ * RMB
+ * LOCK rq->lock
+ * [S] ->on_rq = 0; [L] ->on_cpu
+ *
+ * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
+ * from the consecutive calls to schedule(); the first switching to our
+ * task, the second putting it to sleep.
+ */
+ smp_rmb();
+
+ /*
* If the owning (remote) cpu is still in the middle of schedule() with
* this task as prev, wait until its done referencing the task.
*/
while (p->on_cpu)
cpu_relax();
/*
- * Pairs with the smp_wmb() in finish_lock_switch().
+ * Combined with the control dependency above, we have an effective
+ * smp_load_acquire() without the need for full barriers.
+ *
+ * Pairs with the smp_store_release() in finish_lock_switch().
+ *
+ * This ensures that tasks getting woken will be fully ordered against
+ * their previous state and preserve Program Order.
*/
smp_rmb();
@@ -2039,7 +2064,6 @@ out:
*/
int wake_up_process(struct task_struct *p)
{
- WARN_ON(task_is_stopped_or_traced(p));
return try_to_wake_up(p, TASK_NORMAL, 0);
}
EXPORT_SYMBOL(wake_up_process);
@@ -5847,13 +5871,13 @@ static int init_rootdomain(struct root_domain *rd)
{
memset(rd, 0, sizeof(*rd));
- if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))
goto out;
- if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))
goto free_span;
- if (!alloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
goto free_online;
- if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
goto free_dlo_mask;
init_dl_bw(&rd->dl_bw);
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 26a54461bf59..05de80b48586 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -788,6 +788,9 @@ cputime_t task_gtime(struct task_struct *t)
unsigned int seq;
cputime_t gtime;
+ if (!context_tracking_is_enabled())
+ return t->gtime;
+
do {
seq = read_seqbegin(&t->vtime_seqlock);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index e3cc16312046..8ec86abe0ea1 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -64,7 +64,7 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
raw_spin_unlock(&rt_b->rt_runtime_lock);
}
-#ifdef CONFIG_SMP
+#if defined(CONFIG_SMP) && defined(HAVE_RT_PUSH_IPI)
static void push_irq_work_func(struct irq_work *work);
#endif
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index efd3bfc7e347..b242775bf670 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1073,6 +1073,9 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
* We must ensure this doesn't happen until the switch is completely
* finished.
*
+ * In particular, the load of prev->state in finish_task_switch() must
+ * happen before this.
+ *
* Pairs with the control dependency and rmb in try_to_wake_up().
*/
smp_store_release(&prev->on_cpu, 0);
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 052e02672d12..f10bd873e684 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -583,18 +583,18 @@ EXPORT_SYMBOL(wake_up_atomic_t);
__sched int bit_wait(struct wait_bit_key *word)
{
- if (signal_pending_state(current->state, current))
- return 1;
schedule();
+ if (signal_pending(current))
+ return -EINTR;
return 0;
}
EXPORT_SYMBOL(bit_wait);
__sched int bit_wait_io(struct wait_bit_key *word)
{
- if (signal_pending_state(current->state, current))
- return 1;
io_schedule();
+ if (signal_pending(current))
+ return -EINTR;
return 0;
}
EXPORT_SYMBOL(bit_wait_io);
@@ -602,11 +602,11 @@ EXPORT_SYMBOL(bit_wait_io);
__sched int bit_wait_timeout(struct wait_bit_key *word)
{
unsigned long now = READ_ONCE(jiffies);
- if (signal_pending_state(current->state, current))
- return 1;
if (time_after_eq(now, word->timeout))
return -EAGAIN;
schedule_timeout(word->timeout - now);
+ if (signal_pending(current))
+ return -EINTR;
return 0;
}
EXPORT_SYMBOL_GPL(bit_wait_timeout);
@@ -614,11 +614,11 @@ EXPORT_SYMBOL_GPL(bit_wait_timeout);
__sched int bit_wait_io_timeout(struct wait_bit_key *word)
{
unsigned long now = READ_ONCE(jiffies);
- if (signal_pending_state(current->state, current))
- return 1;
if (time_after_eq(now, word->timeout))
return -EAGAIN;
io_schedule_timeout(word->timeout - now);
+ if (signal_pending(current))
+ return -EINTR;
return 0;
}
EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
--
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