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authorChristoph Hellwig <hch@lst.de>2014-01-23 12:07:41 +0100
committerChristoph Hellwig <hch@lst.de>2014-07-25 17:15:48 -0400
commitcd9070c9c512ff7995f9019392e0ae548df3a088 (patch)
treea426fccd5633f429f37dac237d8cf417ad9e7f31 /include/scsi/scsi_device.h
parent71e75c97f97a9645d25fbf3d8e4165a558f18747 (diff)
downloadblackbird-op-linux-cd9070c9c512ff7995f9019392e0ae548df3a088.tar.gz
blackbird-op-linux-cd9070c9c512ff7995f9019392e0ae548df3a088.zip
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 <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Webb Scales <webbnh@hp.com> Acked-by: Jens Axboe <axboe@kernel.dk> Tested-by: Bart Van Assche <bvanassche@acm.org> Tested-by: Robert Elliott <elliott@hp.com>
Diffstat (limited to 'include/scsi/scsi_device.h')
-rw-r--r--include/scsi/scsi_device.h7
1 files changed, 4 insertions, 3 deletions
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
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