Re: Reproducible deadlock when usb-storage scsi command timeouts twice

[Maxime Bizon <mbizon@freebox.fr>]

On Thursday 04 May 2023 à 10:05:38 (-0400), Alan Stern wrote:

> Maxime, would you like to submit a revised version of your patch?  The 
> key difference is that it should abort the currently executing command 
> (if there is one), regardless of whether the srb value matches.

Yes

before I do a format submission, is this what you have in mind ?

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 8931df5a85fd..380b04273969 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -406,10 +406,8 @@ static DEF_SCSI_QCMD(queuecommand)
  ***********************************************************************/
 
 /* Command timeout and abort */
-static int command_abort(struct scsi_cmnd *srb)
+static int command_abort_matching(struct us_data *us, struct scsi_cmnd *srb_match)
 {
-	struct us_data *us = host_to_us(srb->device->host);
-
 	usb_stor_dbg(us, "%s called\n", __func__);
 
 	/*
@@ -418,10 +416,17 @@ static int command_abort(struct scsi_cmnd *srb)
 	 */
 	scsi_lock(us_to_host(us));
 
-	/* Is this command still active? */
-	if (us->srb != srb) {
+	/* is there any active pending command to abort ? */
+	if (!us->srb) {
 		scsi_unlock(us_to_host(us));
 		usb_stor_dbg(us, "-- nothing to abort\n");
+		return SUCCESS;
+	}
+
+	/* Does the command match the passed srb if any ? */
+	if (srb_match && us->srb != srb_match) {
+		scsi_unlock(us_to_host(us));
+		usb_stor_dbg(us, "-- pending command mismatch\n");
 		return FAILED;
 	}
 
@@ -444,6 +449,16 @@ static int command_abort(struct scsi_cmnd *srb)
 	return SUCCESS;
 }
 
+static int command_abort_any(struct us_data *us)
+{
+	return command_abort_matching(us, NULL);
+}
+
+static int command_abort(struct scsi_cmnd *srb)
+{
+	return command_abort_matching(host_to_us(srb->device->host), srb);
+}
+
 /*
  * This invokes the transport reset mechanism to reset the state of the
  * device
@@ -455,6 +470,8 @@ static int device_reset(struct scsi_cmnd *srb)
 
 	usb_stor_dbg(us, "%s called\n", __func__);
 
+	command_abort_any(us);
+
 	/* lock the device pointers and do the reset */
 	mutex_lock(&(us->dev_mutex));
 	result = us->transport_reset(us);


-- 
Maxime