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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_host.h
parent71e75c97f97a9645d25fbf3d8e4165a558f18747 (diff)
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_host.h')
-rw-r--r--include/scsi/scsi_host.h7
1 files changed, 2 insertions, 5 deletions
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 51f7911b1cbb..5e8ebc1ac12b 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -583,6 +583,8 @@ struct Scsi_Host {
struct blk_queue_tag *bqt;
atomic_t host_busy; /* commands actually active on low-level */
+ atomic_t host_blocked;
+
unsigned int host_failed; /* commands that failed.
protected by host_lock */
unsigned int host_eh_scheduled; /* EH scheduled without command */
@@ -682,11 +684,6 @@ struct Scsi_Host {
struct workqueue_struct *tmf_work_q;
/*
- * Host has rejected a command because it was busy.
- */
- unsigned int host_blocked;
-
- /*
* Value host_blocked counts down from
*/
unsigned int max_host_blocked;