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sched, rcu: Make RCU use resched_cpu()

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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@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/n/tip-2eywnacjl1nllctl1nszqa5w@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
2013-09-17 09:30:55 +02:00
committed by Ingo Molnar
parent 0c44c2d0f4
commit b021fe3e25
2 changed files with 16 additions and 9 deletions
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15
kernel/rcutree.c
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@@ -898,6 +898,12 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
force_quiescent_state(rsp); /* Kick them all. */ 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) static void print_cpu_stall(struct rcu_state *rsp)
{ {
int cpu; int cpu;
@@ -927,7 +933,14 @@ static void print_cpu_stall(struct rcu_state *rsp)
3 * rcu_jiffies_till_stall_check() + 3; 3 * rcu_jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags); 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) static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)

10
kernel/sched/core.c
View File

@@ -513,12 +513,11 @@ static inline void init_hrtick(void)
* might also involve a cross-CPU call to trigger the scheduler on * might also involve a cross-CPU call to trigger the scheduler on
* the target CPU. * the target CPU.
*/ */
#ifdef CONFIG_SMP
void resched_task(struct task_struct *p) void resched_task(struct task_struct *p)
{ {
int cpu; int cpu;
assert_raw_spin_locked(&task_rq(p)->lock); lockdep_assert_held(&task_rq(p)->lock);
if (test_tsk_need_resched(p)) if (test_tsk_need_resched(p))
return; return;
@@ -546,6 +545,7 @@ void resched_cpu(int cpu)
raw_spin_unlock_irqrestore(&rq->lock, flags); raw_spin_unlock_irqrestore(&rq->lock, flags);
} }
#ifdef CONFIG_SMP
#ifdef CONFIG_NO_HZ_COMMON #ifdef CONFIG_NO_HZ_COMMON
/* /*
* In the semi idle case, use the nearest busy cpu for migrating timers * 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 */ #endif /* CONFIG_SMP */
#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \ #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \