locking/rwsem: Simplify the is-owner-spinnable checks
Add the trivial owner_on_cpu() helper for rwsem_can_spin_on_owner() and rwsem_spin_on_owner(), it also allows to make rwsem_can_spin_on_owner() a bit more clear. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Waiman Long <longman@redhat.com> Cc: Amir Goldstein <amir73il@gmail.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Jan Kara <jack@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Theodore Y. Ts'o <tytso@mit.edu> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20180518165534.GA22348@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -347,6 +347,15 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
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}
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}
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static inline bool owner_on_cpu(struct task_struct *owner)
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{
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/*
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* As lock holder preemption issue, we both skip spinning if
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* task is not on cpu or its cpu is preempted
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*/
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return owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
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}
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static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
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{
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struct task_struct *owner;
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@ -359,17 +368,10 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
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rcu_read_lock();
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owner = READ_ONCE(sem->owner);
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if (!owner || !is_rwsem_owner_spinnable(owner)) {
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ret = !owner; /* !owner is spinnable */
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goto done;
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if (owner) {
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ret = is_rwsem_owner_spinnable(owner) &&
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owner_on_cpu(owner);
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}
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/*
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* As lock holder preemption issue, we both skip spinning if task is not
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* on cpu or its cpu is preempted
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*/
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ret = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
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done:
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rcu_read_unlock();
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return ret;
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}
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@ -398,8 +400,7 @@ static noinline bool rwsem_spin_on_owner(struct rw_semaphore *sem)
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* abort spinning when need_resched or owner is not running or
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* owner's cpu is preempted.
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*/
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if (!owner->on_cpu || need_resched() ||
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vcpu_is_preempted(task_cpu(owner))) {
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if (need_resched() || !owner_on_cpu(owner)) {
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rcu_read_unlock();
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return false;
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}
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