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Groups > linux.kernel > #1678320

[PATCH RFC 07/26] drivers/ata: Replace spin_unlock_wait() with lock/unlock pair

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject [PATCH RFC 07/26] drivers/ata: Replace spin_unlock_wait() with lock/unlock pair
Date 2017-06-30 02:10 +0200
Message-ID <tXRFx-6oX-41@gated-at.bofh.it> (permalink)
References <tXRvP-663-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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 ef68232b5222..779f6f18c1f4 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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Thread

[PATCH RFC 0/26] Remove spin_unlock_wait() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:00 +0200
  [PATCH RFC 13/26] blackfin: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 08/26] locking: Remove spin_unlock_wait() generic definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
    Re: [PATCH RFC 08/26] locking: Remove spin_unlock_wait() generic  definitions Will Deacon <will.deacon@arm.com> - 2017-06-30 11:20 +0200
      Re: [PATCH RFC 08/26] locking: Remove spin_unlock_wait() generic  definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 14:50 +0200
        Re: [PATCH RFC 08/26] locking: Remove spin_unlock_wait() generic  definitions Will Deacon <will.deacon@arm.com> - 2017-06-30 15:20 +0200
          Re: [PATCH RFC 08/26] locking: Remove spin_unlock_wait() generic  definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-01 00:20 +0200
            Re: [PATCH RFC 08/26] locking: Remove spin_unlock_wait() generic  definitions Will Deacon <will.deacon@arm.com> - 2017-07-03 15:20 +0200
  [PATCH RFC 23/26] sh: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 16/26] m32r: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 21/26] powerpc: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
    Re: [PATCH RFC 21/26] powerpc: Remove spin_unlock_wait()  arch-specific definitions Boqun Feng <boqun.feng@gmail.com> - 2017-07-02 06:00 +0200
  [PATCH RFC 25/26] tile: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
    Re: [PATCH RFC 25/26] tile: Remove spin_unlock_wait() arch-specific definitions Linus Torvalds <torvalds@linux-foundation.org> - 2017-06-30 02:10 +0200
      Re: [PATCH RFC 25/26] tile: Remove spin_unlock_wait() arch-specific definitions Linus Torvalds <torvalds@linux-foundation.org> - 2017-06-30 02:20 +0200
        Re: [PATCH RFC 25/26] tile: Remove spin_unlock_wait() arch-specific  definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:30 +0200
      Re: [PATCH RFC 25/26] tile: Remove spin_unlock_wait() arch-specific  definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:20 +0200
      Re: [PATCH RFC 25/26] tile: Remove spin_unlock_wait() arch-specific  definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:20 +0200
  [PATCH RFC 18/26] mips: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 19/26] mn10300: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 20/26] parisc: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 15/26] ia64: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 11/26] arm: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 22/26] s390: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 01/26] netfilter: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
    Re: [PATCH RFC 01/26] netfilter: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-02 04:10 +0200
  [PATCH RFC 04/26] completion: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 07/26] drivers/ata: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 14/26] hexagon: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 09/26] alpha: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 24/26] sparc: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 26/26] xtensa: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:10 +0200
  [PATCH RFC 03/26] sched: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:20 +0200
    Re: [PATCH RFC 03/26] sched: Replace spin_unlock_wait() with  lock/unlock pair Arnd Bergmann <arnd@arndb.de> - 2017-06-30 12:40 +0200
      Re: [PATCH RFC 03/26] sched: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 14:40 +0200
  [PATCH RFC 05/26] exit: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:20 +0200
  [PATCH RFC 12/26] arm64: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:20 +0200
    Re: [PATCH RFC 12/26] arm64: Remove spin_unlock_wait() arch-specific  definitions Will Deacon <will.deacon@arm.com> - 2017-06-30 11:30 +0200
      Re: [PATCH RFC 12/26] arm64: Remove spin_unlock_wait() arch-specific  definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 19:40 +0200
  [PATCH RFC 10/26] arc: Remove spin_unlock_wait() arch-specific definitions "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:20 +0200
  [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 02:20 +0200
    Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair Oleg Nesterov <oleg@redhat.com> - 2017-06-30 13:10 +0200
      Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 15:00 +0200
        Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair Oleg Nesterov <oleg@redhat.com> - 2017-06-30 17:30 +0200
          Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 18:20 +0200
            Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 19:30 +0200
            Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair Oleg Nesterov <oleg@redhat.com> - 2017-06-30 21:30 +0200
              Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair Alan Stern <stern@rowland.harvard.edu> - 2017-06-30 22:00 +0200
                Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 22:10 +0200
              Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 22:10 +0200
                Re: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-30 22:20 +0200
  Re: [PATCH RFC 06/26] ipc: Replace spin_unlock_wait() with  lock/unlock pair Manfred Spraul <manfred@colorfullife.com> - 2017-07-01 21:30 +0200
    Re: [PATCH RFC 06/26] ipc: Replace spin_unlock_wait() with  lock/unlock pair "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-02 05:20 +0200

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