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Commit 44b93b59 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by James Bottomley
Browse files

[SCSI] avoid useless free_list lock roundtrips 



Avoid hitting the host-wide free_list lock unless we need to put a command
back onto the freelist.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent df03c3f6

drivers/scsi/scsi.c

+6 −5
Original line number Diff line number Diff line
@@ -320,13 +320,14 @@ 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))) {

		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);

	}



	if (likely(cmd != NULL))

		scsi_pool_free_command(shost->cmd_pool, cmd);