Commit-ID: b021fe3e25094fbec22d0eff846d2adeee1b9736
Gitweb: http://git.kernel.org/tip/b021fe3e25094fbec22d0eff846d2adeee1b9736
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 17 Sep 2013 09:30:55 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 25 Sep 2013 13:53:08 +0200
sched, rcu: Make RCU use resched_cpu()
We're going to deprecate and remove set_need_resched() for it will do
the wrong thing. Make an exception for RCU and allow it to use
resched_cpu() which will do the right thing.
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-2eywnacjl1nllctl1nszqa5w@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/rcutree.c | 15 ++++++++++++++-
kernel/sched/core.c | 10 ++--------
2 files changed, 16 insertions(+), 9 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 32618b3..1dc9f36 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -898,6 +898,12 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
force_quiescent_state(rsp); /* Kick them all. */
}
+/*
+ * This function really isn't for public consumption, but RCU is special in
+ * that context switches can allow the state machine to make progress.
+ */
+extern void resched_cpu(int cpu);
+
static void print_cpu_stall(struct rcu_state *rsp)
{
int cpu;
@@ -927,7 +933,14 @@ static void print_cpu_stall(struct rcu_state *rsp)
3 * rcu_jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
- set_need_resched(); /* kick ourselves to get things going. */
+ /*
+ * Attempt to revive the RCU machinery by forcing a context switch.
+ *
+ * A context switch would normally allow the RCU state machine to make
+ * progress and it could be we're stuck in kernel space without context
+ * switches for an entirely unreasonable amount of time.
+ */
+ resched_cpu(smp_processor_id());
}
static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ac57967..242da0c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -513,12 +513,11 @@ static inline void init_hrtick(void)
* might also involve a cross-CPU call to trigger the scheduler on
* the target CPU.
*/
-#ifdef CONFIG_SMP
void resched_task(struct task_struct *p)
{
int cpu;
- assert_raw_spin_locked(&task_rq(p)->lock);
+ lockdep_assert_held(&task_rq(p)->lock);
if (test_tsk_need_resched(p))
return;
@@ -546,6 +545,7 @@ void resched_cpu(int cpu)
raw_spin_unlock_irqrestore(&rq->lock, flags);
}
+#ifdef CONFIG_SMP
#ifdef CONFIG_NO_HZ_COMMON
/*
* In the semi idle case, use the nearest busy cpu for migrating timers
@@ -693,12 +693,6 @@ void sched_avg_update(struct rq *rq)
}
}
-#else /* !CONFIG_SMP */
-void resched_task(struct task_struct *p)
-{
- assert_raw_spin_locked(&task_rq(p)->lock);
- set_tsk_need_resched(p);
-}
#endif /* CONFIG_SMP */
#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
--
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