From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: [PATCH 04/17] scsi: avoid useless free_list lock roundtrips Date: Wed, 05 Feb 2014 04:39:34 -0800 Message-ID: <20140205124019.577883829@bombadil.infradead.org> References: <20140205123930.150608699@bombadil.infradead.org> Return-path: Received: from bombadil.infradead.org ([198.137.202.9]:53194 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751287AbaBEMkZ (ORCPT ); Wed, 5 Feb 2014 07:40:25 -0500 Content-Disposition: inline; filename=0004-scsi-avoid-useless-free_list-lock-roundtrips.patch Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jens Axboe , James Bottomley , Nicholas Bellinger Cc: linux-scsi@vger.kernel.org Avoid hitting the host-wide free_list lock unless we need to put a command back onto the freelist. Signed-off-by: Christoph Hellwig --- drivers/scsi/scsi.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index ebcea6c..4139486 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -320,15 +320,16 @@ void __scsi_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd, { unsigned long flags; - /* changing locks here, don't need to restore the irq state */ - spin_lock_irqsave(&shost->free_list_lock, flags); if (unlikely(list_empty(&shost->free_list))) { - list_add(&cmd->list, &shost->free_list); - cmd = NULL; + spin_lock_irqsave(&shost->free_list_lock, flags); + if (list_empty(&shost->free_list)) { + list_add(&cmd->list, &shost->free_list); + cmd = NULL; + } + spin_unlock_irqrestore(&shost->free_list_lock, flags); } - spin_unlock_irqrestore(&shost->free_list_lock, flags); - if (likely(cmd != NULL)) + if (cmd) scsi_pool_free_command(shost->cmd_pool, cmd); put_device(dev); -- 1.7.10.4