Commit c0bed69d authored by Kefeng Wang's avatar Kefeng Wang Committed by Peter Zijlstra
Browse files

locking: Make owner_on_cpu() into <linux/sched.h> 



Move the owner_on_cpu() from kernel/locking/rwsem.c into
include/linux/sched.h with under CONFIG_SMP, then use it
in the mutex/rwsem/rtmutex to simplify the code.

Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211203075935.136808-2-wangkefeng.wang@huawei.com
parent 9a75bd0c

include/linux/sched.h

+9 −0
Original line number Diff line number Diff line
@@ -2171,6 +2171,15 @@ extern long sched_getaffinity(pid_t pid, struct cpumask *mask); 
#endif



#ifdef CONFIG_SMP

static inline bool owner_on_cpu(struct task_struct *owner)

{

	/*

	 * As lock holder preemption issue, we both skip spinning if

	 * task is not on cpu or its cpu is preempted

	 */

	return owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));

}



/* Returns effective CPU energy utilization, as seen by the scheduler */

unsigned long sched_cpu_util(int cpu, unsigned long max);

#endif /* CONFIG_SMP */

kernel/locking/mutex.c

+2 −9
Original line number Diff line number Diff line
@@ -367,8 +367,7 @@ bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner, 
		/*

		 * Use vcpu_is_preempted to detect lock holder preemption issue.

		 */

		if (!owner->on_cpu || need_resched() ||

				vcpu_is_preempted(task_cpu(owner))) {

		if (!owner_on_cpu(owner) || need_resched()) {

			ret = false;

			break;

		}
@@ -403,14 +402,8 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock) 
	 * structure won't go away during the spinning period.

	 */

	owner = __mutex_owner(lock);



	/*

	 * As lock holder preemption issue, we both skip spinning if task is not

	 * on cpu or its cpu is preempted

	 */



	if (owner)

		retval = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));

		retval = owner_on_cpu(owner);



	/*

	 * If lock->owner is not set, the mutex has been released. Return true

kernel/locking/rtmutex.c

+2 −3
Original line number Diff line number Diff line
@@ -1382,9 +1382,8 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock, 
		 *    for CONFIG_PREEMPT_RCU=y)

		 *  - the VCPU on which owner runs is preempted

		 */

		if (!owner->on_cpu || need_resched() ||

		    rt_mutex_waiter_is_top_waiter(lock, waiter) ||

		    vcpu_is_preempted(task_cpu(owner))) {

		if (!owner_on_cpu(owner) || need_resched() ||

		    rt_mutex_waiter_is_top_waiter(lock, waiter)) {

			res = false;

			break;

		}

kernel/locking/rwsem.c

+0 −9
Original line number Diff line number Diff line
@@ -613,15 +613,6 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem) 
	return false;

}



static inline bool owner_on_cpu(struct task_struct *owner)

{

	/*

	 * As lock holder preemption issue, we both skip spinning if

	 * task is not on cpu or its cpu is preempted

	 */

	return owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));

}



static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)

{

	struct task_struct *owner;