Commit-ID: 1b22fc609cecd1b16c4a015e1a6b3c9717484e3a Gitweb: https://git.kernel.org/tip/1b22fc609cecd1b16c4a015e1a6b3c9717484e3a Author: Oleg Nesterov <[email protected]> AuthorDate: Fri, 18 May 2018 18:55:35 +0200 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 25 May 2018 08:11:47 +0200
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 <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Waiman Long <[email protected]> Cc: Amir Goldstein <[email protected]> Cc: Davidlohr Bueso <[email protected]> Cc: Jan Kara <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Theodore Y. Ts'o <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/locking/rwsem-xadd.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index a90336779375..3064c50e181e 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -347,6 +347,15 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem) } } +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; @@ -359,17 +368,10 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) rcu_read_lock(); owner = READ_ONCE(sem->owner); - if (!owner || !is_rwsem_owner_spinnable(owner)) { - ret = !owner; /* !owner is spinnable */ - goto done; + if (owner) { + ret = is_rwsem_owner_spinnable(owner) && + owner_on_cpu(owner); } - - /* - * As lock holder preemption issue, we both skip spinning if task is not - * on cpu or its cpu is preempted - */ - ret = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner)); -done: rcu_read_unlock(); return ret; } @@ -398,8 +400,7 @@ static noinline bool rwsem_spin_on_owner(struct rw_semaphore *sem) * abort spinning when need_resched or owner is not running or * owner's cpu is preempted. */ - if (!owner->on_cpu || need_resched() || - vcpu_is_preempted(task_cpu(owner))) { + if (need_resched() || !owner_on_cpu(owner)) { rcu_read_unlock(); return false; }
