On 05/21/2014 03:30 PM, Bart Van Assche wrote:
scmd->abort_work is only scheduled after the block layer has marked
the request associated with a command as complete and for commands
that are not on the eh_cmd_q list. A SCSI command is only requeued
after the scmd->abort_work handler has started (requeueing clears
the "complete" flag). This means that the cancel_delayed_work()
statement in scsi_put_command() is a no-op. Hence remove it.
Hmm.
I've put in the cancel_delayed_work() as a safety guard, fully
aware that it's one of the "this cannot happen" kind of things.
But there is a workqueue and it might have elements on it.
And when freeing a command we absolutely need to make sure that
the workqueue is empty.
So calling cancel_delayed_work() was the obvious thing to do.
I'd be fine with adding a WARN_ON(!list_empty(&cmd->abort_work))
here, however. This will clear up the intent of this statement.
Additionally, document how it is avoided that scsi_finish_command()
and the SCSI error handler code are invoked concurrently for the
same command via WARN_ON_ONCE() statements. This should avoid that
the scsi error handler code confuses its readers.
This I'd rather put into a separate patch, as it's really a
different issue.
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Cc: Joe Lawrence <jdl1291@xxxxxxxxx>
---
block/blk-softirq.c | 6 ++++++
drivers/scsi/scsi.c | 2 --
drivers/scsi/scsi_error.c | 28 ++++++++++++++++++++++++++++
include/linux/blkdev.h | 1 +
4 files changed, 35 insertions(+), 2 deletions(-)
diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 53b1737..59bb52d 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -172,6 +172,12 @@ void blk_complete_request(struct request *req)
}
EXPORT_SYMBOL(blk_complete_request);
+bool blk_rq_completed(struct request *rq)
+{
+ return test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
+}
+EXPORT_SYMBOL(blk_rq_completed);
+
static __init int blk_softirq_init(void)
{
int i;
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 88d46fe..04a282a 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -334,8 +334,6 @@ void scsi_put_command(struct scsi_cmnd *cmd)
list_del_init(&cmd->list);
spin_unlock_irqrestore(&cmd->device->list_lock, flags);
- cancel_delayed_work(&cmd->abort_work);
-
__scsi_put_command(cmd->device->host, cmd);
}
EXPORT_SYMBOL(scsi_put_command);
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 14ce3b4..32a8cd1 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -108,6 +108,28 @@ static int scsi_host_eh_past_deadline(struct Scsi_Host *shost)
return 1;
}
+static bool scmd_being_handled_in_other_context(struct scsi_cmnd *scmd)
+{
+ struct Scsi_Host *shost = scmd->device->host;
+ struct scsi_cmnd *c;
+ unsigned long flags;
+ bool ret = false;
+
+ if (!blk_rq_completed(scmd->request))
+ return true;
+
+ spin_lock_irqsave(shost->host_lock, flags);
+ list_for_each_entry(c, &shost->eh_cmd_q, eh_entry) {
+ if (c == scmd) {
+ ret = true;
+ break;
+ }
+ }
+ spin_unlock_irqrestore(shost->host_lock, flags);
+
+ return ret;
+}
+
/**
* scmd_eh_abort_handler - Handle command aborts
* @work: command to be aborted.
Can't we just check for
!list_empty(&scmd->eh_entry)
here?
Should achieve the same with less computation...
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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