[...]
Willy pointed out a bogus hunk in the original patch that should not
have been there. Retransmit with that removed. Also mark scsi_cmnd_serial
inline.
This patch fixes one of Christroph's fixme comments in the SCSI midlayer.
The selection of the serial number and pid for commands was done
by a global variable and not SMP safe. The race was not very
serious because it was only used for error handling, but it's
still better to fix it.
I audited all the drivers and none seemed to use them
for anything interesting, so I just made it a per host counter
protected by host lock.
(in fact they could be probably removed because they only see
to be used as a flag in exception handling and for debugging.
The patch would be unfortunately quite big because a lot
of driver printks use them)
This should be slight faster on SMP too because the cache line of
the counter won't bounce around the machine.
diff -u linux-2.6.11rc3/drivers/scsi/scsi.c-SCSISER
linux-2.6.11rc3/drivers/scsi/scsi.c
--- linux-2.6.11rc3/drivers/scsi/scsi.c-SCSISER 2005-02-04 09:13:14.000000000
+0100
+++ linux-2.6.11rc3/drivers/scsi/scsi.c 2005-02-05 12:02:50.000000000 +0100
@@ -88,12 +88,6 @@
COMMAND_SIZE((cmd)->cmnd[0]) : (cmd)->cmd_len)
/*
- * Data declarations.
- */
-unsigned long scsi_pid;
-static unsigned long serial_number;
-
-/*
* Note - the initial logging level can be set here to log events at boot time.
* After the system is up, you may enable logging via the /proc interface.
*/
@@ -510,6 +504,21 @@
}
#endif
+/*
+ * Assign a serial number and pid to the request for error recovery
+ * and debugging purposes. Protected by the Host_Lock of host.
+ */
+static inline void scsi_cmd_get_serial(struct Scsi_Host *host, struct
scsi_cmnd *cmd)
+{
+ cmd->serial_number = host->cmd_serial_number++;
+ if (cmd->serial_number == 0)
+ cmd->serial_number = host->cmd_serial_number++;
+
+ cmd->pid = host->cmd_pid++;
+ if (cmd->pid == 0)
+ cmd->pid = host->cmd_pid++;
+}
+
/*
* Function: scsi_dispatch_command
*
@@ -556,13 +565,6 @@
goto out;
}
- /* Assign a unique nonzero serial_number. */
- /* XXX(hch): this is racy */
- if (++serial_number == 0)
- serial_number = 1;
- cmd->serial_number = serial_number;
- cmd->pid = scsi_pid++;
-
/*
* If SCSI-2 or lower, store the LUN value in cmnd.
*/
@@ -593,6 +595,10 @@
host->resetting = 0;
}
+ /*
+ * AK: unlikely race here: for some reason the timer could
+ * expire before the serial number is set up below.
+ */
scsi_add_timer(cmd, cmd->timeout_per_command, scsi_times_out);
scsi_log_send(cmd);
@@ -619,6 +625,8 @@
}
spin_lock_irqsave(host->host_lock, flags);
+ scsi_cmd_get_serial(host, cmd);
+
if (unlikely(test_bit(SHOST_CANCEL, &host->shost_state))) {
cmd->result = (DID_NO_CONNECT << 16);
scsi_done(cmd);
diff -u linux-2.6.11rc3/include/scsi/scsi_cmnd.h-SCSISER
linux-2.6.11rc3/include/scsi/scsi_cmnd.h
--- linux-2.6.11rc3/include/scsi/scsi_cmnd.h-SCSISER 2004-05-10
09:44:25.000000000 +0200
+++ linux-2.6.11rc3/include/scsi/scsi_cmnd.h 2005-02-05 09:28:31.000000000
+0100
@@ -54,6 +54,7 @@
* completed and the SCSI Command structure has already being reused
* for another command, so that we can avoid incorrectly aborting or
* resetting the new command.
+ * The serial number is only unique per host.
*/
unsigned long serial_number;
unsigned long serial_number_at_timeout;
@@ -139,7 +140,7 @@
int result; /* Status code from lower level driver */
unsigned char tag; /* SCSI-II queued command tag */
- unsigned long pid; /* Process ID, starts at 0 */
+ unsigned long pid; /* Process ID, starts at 0. Unique per host. */
};
/*
diff -u linux-2.6.11rc3/include/scsi/scsi_host.h-SCSISER
linux-2.6.11rc3/include/scsi/scsi_host.h
--- linux-2.6.11rc3/include/scsi/scsi_host.h-SCSISER 2005-02-04
09:13:50.000000000 +0100
+++ linux-2.6.11rc3/include/scsi/scsi_host.h 2005-02-05 12:02:17.000000000
+0100
@@ -483,7 +483,12 @@
short unsigned int sg_tablesize;
short unsigned int max_sectors;
unsigned long dma_boundary;
-
+ /*
+ * Used to assign serial numbers to the cmds.
+ * Protected by the host lock.
+ */
+ unsigned long cmd_serial_number, cmd_pid;
+
unsigned unchecked_isa_dma:1;
unsigned use_clustering:1;
unsigned use_blk_tcq:1;
-
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
