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Groups > linux.kernel > #1695185

[PATCH tip/core/rcu 7/9] drivers/ata: Replace spin_unlock_wait() with lock/unlock pair

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There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair.  This commit therefore eliminates the spin_unlock_wait() call and
associated else-clause and hoists the then-clause's lock and unlock out of
the "if" statement.  This should be safe from a performance perspective
because according to Tejun there should be few if any drivers that don't
set their own error handler.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: <linux-ide@vger.kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
 drivers/ata/libata-eh.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index b70bcf6d2914..b325db27eb8c 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -645,12 +645,11 @@ void ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
 	 * completions are honored.  A scmd is determined to have
 	 * timed out iff its associated qc is active and not failed.
 	 */
+	spin_lock_irqsave(ap->lock, flags);
 	if (ap->ops->error_handler) {
 		struct scsi_cmnd *scmd, *tmp;
 		int nr_timedout = 0;
 
-		spin_lock_irqsave(ap->lock, flags);
-
 		/* This must occur under the ap->lock as we don't want
 		   a polled recovery to race the real interrupt handler
 
@@ -700,12 +699,11 @@ void ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
 		if (nr_timedout)
 			__ata_port_freeze(ap);
 
-		spin_unlock_irqrestore(ap->lock, flags);
 
 		/* initialize eh_tries */
 		ap->eh_tries = ATA_EH_MAX_TRIES;
-	} else
-		spin_unlock_wait(ap->lock);
+	}
+	spin_unlock_irqrestore(ap->lock, flags);
 
 }
 EXPORT_SYMBOL(ata_scsi_cmd_error_handler);
-- 
2.5.2

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[PATCH tip/core/rcu 0/9] Remove spin_unlock_wait() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 1/9] net/netfilter/nf_conntrack_core: Fix net_conntrack_lock() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 3/9] sched: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 5/9] exit: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 2/9] task_work: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 8/9] locking: Remove spin_unlock_wait() generic definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 7/9] drivers/ata: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 9/9] arch: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 6/9] ipc: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200
  [PATCH tip/core/rcu 4/9] completion: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:20 +0200

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