From cd9070c9c512ff7995f9019392e0ae548df3a088 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 23 Jan 2014 12:07:41 +0100 Subject: scsi: fix the {host,target,device}_blocked counter mess Seems like these counters are missing any sort of synchronization for updates, as a over 10 year old comment from me noted. Fix this by using atomic counters, and while we're at it also make sure they are in the same cacheline as the _busy counters and not needlessly stored to in every I/O completion. With the new model the _busy counters can temporarily go negative, so all the readers are updated to check for > 0 values. Longer term every successful I/O completion will reset the counters to zero, so the temporarily negative values will not cause any harm. Signed-off-by: Christoph Hellwig Reviewed-by: Martin K. Petersen Reviewed-by: Webb Scales Acked-by: Jens Axboe Tested-by: Bart Van Assche Tested-by: Robert Elliott --- include/scsi/scsi_device.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'include/scsi/scsi_device.h') diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index 3329901c7243..0f853f2c9dc7 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -82,6 +82,8 @@ struct scsi_device { struct list_head same_target_siblings; /* just the devices sharing same target id */ atomic_t device_busy; /* commands actually active on LLDD */ + atomic_t device_blocked; /* Device returned QUEUE_FULL. */ + spinlock_t list_lock; struct list_head cmd_list; /* queue of in use SCSI Command structures */ struct list_head starved_entry; @@ -180,8 +182,6 @@ struct scsi_device { struct list_head event_list; /* asserted events */ struct work_struct event_work; - unsigned int device_blocked; /* Device returned QUEUE_FULL. */ - unsigned int max_device_blocked; /* what device_blocked counts down from */ #define SCSI_DEFAULT_DEVICE_BLOCKED 3 @@ -291,12 +291,13 @@ struct scsi_target { * the same target will also. */ /* commands actually active on LLD. */ atomic_t target_busy; + atomic_t target_blocked; + /* * LLDs should set this in the slave_alloc host template callout. * If set to zero then there is not limit. */ unsigned int can_queue; - unsigned int target_blocked; unsigned int max_target_blocked; #define SCSI_DEFAULT_TARGET_BLOCKED 3 -- cgit v1.2.3