* [PATCH 3/4] zfcp: Avoid race condition on "link up" event
@ 2007-08-08 8:47 Swen Schillig
2007-08-09 8:10 ` Swen Schillig
0 siblings, 1 reply; 2+ messages in thread
From: Swen Schillig @ 2007-08-08 8:47 UTC (permalink / raw)
To: James Bottomley; +Cc: linux-scsi, linux-s390, schmichr
From: Christoph Schmitt <schmichr@de.ibm.com>
Symptom: zfcp receives a response to a "status read" request
that is no longer valid in zfcp. This leads to a
kernel panic, since some memory has been overwritten
by the response reporting.
Problem: On receiving an "unsolicited status", zfcp issues a
new "status read" request. On receiving the
"unsolicited status" "link up", zfcp triggers an adapter
reopen. The new "status read" request and the reopen
can lead to a race where zfcp issues the request before
the reopen, but the hardware handles the reopen first.
Solution: Not issue the "status read" request to avoid the race
condition. The adapter reopen will enqueue 16 new
"status read" requests anyway.
Signed-off-by: Christoph Schmitt <schmichr@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
---
drivers/s390/scsi/zfcp_fsf.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff -urpN linux-2.6/drivers/s390/scsi/zfcp_fsf.c linux-2.6-patched/drivers/s390/scsi/zfcp_fsf.c
--- linux-2.6/drivers/s390/scsi/zfcp_fsf.c 2007-08-08 10:13:39.000000000 +0200
+++ linux-2.6-patched/drivers/s390/scsi/zfcp_fsf.c 2007-08-08 10:14:03.000000000 +0200
@@ -33,7 +33,7 @@ static int zfcp_fsf_send_fcp_command_tas
static int zfcp_fsf_send_fcp_command_task_management_handler(
struct zfcp_fsf_req *);
static int zfcp_fsf_abort_fcp_command_handler(struct zfcp_fsf_req *);
-static int zfcp_fsf_status_read_handler(struct zfcp_fsf_req *);
+static void zfcp_fsf_status_read_handler(struct zfcp_fsf_req *);
static int zfcp_fsf_send_ct_handler(struct zfcp_fsf_req *);
static int zfcp_fsf_send_els_handler(struct zfcp_fsf_req *);
static int zfcp_fsf_control_file_handler(struct zfcp_fsf_req *);
@@ -856,10 +856,10 @@ zfcp_fsf_status_read_port_closed(struct
*
* returns:
*/
-static int
+static void
zfcp_fsf_status_read_handler(struct zfcp_fsf_req *fsf_req)
{
- int retval = 0;
+ int retval;
struct zfcp_adapter *adapter = fsf_req->adapter;
struct fsf_status_read_buffer *status_buffer =
(struct fsf_status_read_buffer *) fsf_req->data;
@@ -869,7 +869,7 @@ zfcp_fsf_status_read_handler(struct zfcp
zfcp_hba_dbf_event_fsf_unsol("dism", adapter, status_buffer);
mempool_free(status_buffer, adapter->pool.data_status_read);
zfcp_fsf_req_free(fsf_req);
- goto out;
+ return;
}
zfcp_hba_dbf_event_fsf_unsol("read", adapter, status_buffer);
@@ -1061,6 +1061,15 @@ zfcp_fsf_status_read_handler(struct zfcp
* FIXME:
* allocation failure possible? (Is this code needed?)
*/
+ /*
+ * If we triggered an adapter reopen, then the reopen will also
+ * enqueue new status read requests. Not issuing a status read
+ * here avoids a race between the request send and the adapter
+ * reopen.
+ */
+ if (status_buffer->status_type == FSF_STATUS_READ_LINK_UP)
+ return;
+
retval = zfcp_fsf_status_read(adapter, 0);
if (retval < 0) {
ZFCP_LOG_INFO("Failed to create unsolicited status read "
@@ -1076,8 +1085,6 @@ zfcp_fsf_status_read_handler(struct zfcp
zfcp_erp_adapter_reopen(adapter, 0);
}
}
- out:
- return retval;
}
/*
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH 3/4] zfcp: Avoid race condition on "link up" event
2007-08-08 8:47 [PATCH 3/4] zfcp: Avoid race condition on "link up" event Swen Schillig
@ 2007-08-09 8:10 ` Swen Schillig
0 siblings, 0 replies; 2+ messages in thread
From: Swen Schillig @ 2007-08-09 8:10 UTC (permalink / raw)
To: James Bottomley; +Cc: linux-scsi, linux-s390, schmichr
On Wednesday 08 August 2007 10:47, Swen Schillig wrote:
> From: Christoph Schmitt <schmichr@de.ibm.com>
>
> Symptom: zfcp receives a response to a "status read" request
> that is no longer valid in zfcp. This leads to a
> kernel panic, since some memory has been overwritten
> by the response reporting.
> Problem: On receiving an "unsolicited status", zfcp issues a
> new "status read" request. On receiving the
> "unsolicited status" "link up", zfcp triggers an adapter
> reopen. The new "status read" request and the reopen
> can lead to a race where zfcp issues the request before
> the reopen, but the hardware handles the reopen first.
> Solution: Not issue the "status read" request to avoid the race
> condition. The adapter reopen will enqueue 16 new
> "status read" requests anyway.
>
> Signed-off-by: Christoph Schmitt <schmichr@de.ibm.com>
> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
> ---
>
> drivers/s390/scsi/zfcp_fsf.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff -urpN linux-2.6/drivers/s390/scsi/zfcp_fsf.c linux-2.6-patched/drivers/s390/scsi/zfcp_fsf.c
> --- linux-2.6/drivers/s390/scsi/zfcp_fsf.c 2007-08-08 10:13:39.000000000 +0200
> +++ linux-2.6-patched/drivers/s390/scsi/zfcp_fsf.c 2007-08-08 10:14:03.000000000 +0200
> @@ -33,7 +33,7 @@ static int zfcp_fsf_send_fcp_command_tas
> static int zfcp_fsf_send_fcp_command_task_management_handler(
> struct zfcp_fsf_req *);
> static int zfcp_fsf_abort_fcp_command_handler(struct zfcp_fsf_req *);
> -static int zfcp_fsf_status_read_handler(struct zfcp_fsf_req *);
> +static void zfcp_fsf_status_read_handler(struct zfcp_fsf_req *);
> static int zfcp_fsf_send_ct_handler(struct zfcp_fsf_req *);
> static int zfcp_fsf_send_els_handler(struct zfcp_fsf_req *);
> static int zfcp_fsf_control_file_handler(struct zfcp_fsf_req *);
> @@ -856,10 +856,10 @@ zfcp_fsf_status_read_port_closed(struct
> *
> * returns:
> */
> -static int
> +static void
> zfcp_fsf_status_read_handler(struct zfcp_fsf_req *fsf_req)
> {
> - int retval = 0;
> + int retval;
> struct zfcp_adapter *adapter = fsf_req->adapter;
> struct fsf_status_read_buffer *status_buffer =
> (struct fsf_status_read_buffer *) fsf_req->data;
> @@ -869,7 +869,7 @@ zfcp_fsf_status_read_handler(struct zfcp
> zfcp_hba_dbf_event_fsf_unsol("dism", adapter, status_buffer);
> mempool_free(status_buffer, adapter->pool.data_status_read);
> zfcp_fsf_req_free(fsf_req);
> - goto out;
> + return;
> }
>
> zfcp_hba_dbf_event_fsf_unsol("read", adapter, status_buffer);
> @@ -1061,6 +1061,15 @@ zfcp_fsf_status_read_handler(struct zfcp
> * FIXME:
> * allocation failure possible? (Is this code needed?)
> */
> + /*
> + * If we triggered an adapter reopen, then the reopen will also
> + * enqueue new status read requests. Not issuing a status read
> + * here avoids a race between the request send and the adapter
> + * reopen.
> + */
> + if (status_buffer->status_type == FSF_STATUS_READ_LINK_UP)
> + return;
> +
> retval = zfcp_fsf_status_read(adapter, 0);
> if (retval < 0) {
> ZFCP_LOG_INFO("Failed to create unsolicited status read "
> @@ -1076,8 +1085,6 @@ zfcp_fsf_status_read_handler(struct zfcp
> zfcp_erp_adapter_reopen(adapter, 0);
> }
> }
> - out:
> - return retval;
> }
>
> /*
>
James
please dump this patch.
The description is a bit misleading and the issue is solved within our microcode.
Thanks
^ permalink raw reply [flat|nested] 2+ messages in thread
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