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Commit b021fe3e authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 0c44c2d0

kernel/rcutree.c

+14 −1
Original line number Original line Diff line number Diff line
@@ -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)

kernel/sched/core.c

+2 −8
Original line number Original line Diff line number Diff line
@@ -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) && \