Commit-ID: 93edc8bd7750ff3cae088bfca453ea73dc9004a4 Gitweb: http://git.kernel.org/tip/93edc8bd7750ff3cae088bfca453ea73dc9004a4 Author: Waiman Long <waiman.l...@hpe.com> AuthorDate: Fri, 11 Sep 2015 14:37:34 -0400 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Fri, 18 Sep 2015 09:27:29 +0200
locking/pvqspinlock: Kick the PV CPU unconditionally when _Q_SLOW_VAL If _Q_SLOW_VAL has been set, the vCPU state must have been vcpu_hashed. The extra check at the end of __pv_queued_spin_unlock() is unnecessary and can be removed. Signed-off-by: Waiman Long <waiman.l...@hpe.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Reviewed-by: Davidlohr Bueso <d...@stgolabs.net> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Douglas Hatch <doug.ha...@hp.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Scott J Norton <scott.nor...@hp.com> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/1441996658-62854-3-git-send-email-waiman.l...@hpe.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/locking/qspinlock_paravirt.h | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h index c8e6e9a..f0450ff 100644 --- a/kernel/locking/qspinlock_paravirt.h +++ b/kernel/locking/qspinlock_paravirt.h @@ -267,7 +267,6 @@ static void pv_wait_head(struct qspinlock *lock, struct mcs_spinlock *node) } if (!lp) { /* ONCE */ - WRITE_ONCE(pn->state, vcpu_hashed); lp = pv_hash(lock, pn); /* @@ -275,11 +274,9 @@ static void pv_wait_head(struct qspinlock *lock, struct mcs_spinlock *node) * when we observe _Q_SLOW_VAL in __pv_queued_spin_unlock() * we'll be sure to be able to observe our hash entry. * - * [S] pn->state * [S] <hash> [Rmw] l->locked == _Q_SLOW_VAL * MB RMB * [RmW] l->locked = _Q_SLOW_VAL [L] <unhash> - * [L] pn->state * * Matches the smp_rmb() in __pv_queued_spin_unlock(). */ @@ -364,8 +361,7 @@ __visible void __pv_queued_spin_unlock(struct qspinlock *lock) * vCPU is harmless other than the additional latency in completing * the unlock. */ - if (READ_ONCE(node->state) == vcpu_hashed) - pv_kick(node->cpu); + pv_kick(node->cpu); } /* * Include the architecture specific callee-save thunk of the -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
