[S390] tape: deadlock on system work queue

The 34xx and 3590 tape driver uses the system work queue to defer work
from the interrupt function to process context, e.g. a medium sense
after an unsolicited interrupt. The tape commands started by the work
handler need to be asynchronous, otherwise a deadlock on the system
work queue can occur.

Signed-off-by: Martin Schwidefsky <[e-mail]>

drivers/s390/char/tape.h

···
 	return rc;
 }
 
+static inline void
+tape_do_io_async_free(struct tape_device *device, struct tape_request *request)
+{
+	request->callback = (void *) tape_free_request;
+	request->callback_data = NULL;
+	tape_do_io_async(device, request);
+}
+
 extern int tape_oper_handler(int irq, int status);
 extern void tape_noper_handler(int irq, int status);
 extern int tape_open(struct tape_device *);

drivers/s390/char/tape_34xx.c

···
  * Medium sense for 34xx tapes. There is no 'real' medium sense call.
  * So we just do a normal sense.
  */
-static int
-tape_34xx_medium_sense(struct tape_device *device)
+static void __tape_34xx_medium_sense(struct tape_request *request)
 {
-	struct tape_request *request;
-	unsigned char       *sense;
-	int                  rc;
+	struct tape_device *device = request->device;
+	unsigned char *sense;
 
-	request = tape_alloc_request(1, 32);
-	if (IS_ERR(request)) {
-		DBF_EXCEPTION(6, "MSEN fail\n");
-		return PTR_ERR(request);
-	}
-
-	request->op = TO_MSEN;
-	tape_ccw_end(request->cpaddr, SENSE, 32, request->cpdata);
-
-	rc = tape_do_io_interruptible(device, request);
 	if (request->rc == 0) {
 		sense = request->cpdata;
 
···
 			device->tape_generic_status |= GMT_WR_PROT(~0);
 		else
 			device->tape_generic_status &= ~GMT_WR_PROT(~0);
-	} else {
+	} else
 		DBF_EVENT(4, "tape_34xx: medium sense failed with rc=%d\n",
 			request->rc);
-	}
 	tape_free_request(request);
+}
 
+static int tape_34xx_medium_sense(struct tape_device *device)
+{
+	struct tape_request *request;
+	int rc;
+
+	request = tape_alloc_request(1, 32);
+	if (IS_ERR(request)) {
+		DBF_EXCEPTION(6, "MSEN fail\n");
+		return PTR_ERR(request);
+	}
+
+	request->op = TO_MSEN;
+	tape_ccw_end(request->cpaddr, SENSE, 32, request->cpdata);
+	rc = tape_do_io_interruptible(device, request);
+	__tape_34xx_medium_sense(request);
 	return rc;
+}
+
+static void tape_34xx_medium_sense_async(struct tape_device *device)
+{
+	struct tape_request *request;
+
+	request = tape_alloc_request(1, 32);
+	if (IS_ERR(request)) {
+		DBF_EXCEPTION(6, "MSEN fail\n");
+		return;
+	}
+
+	request->op = TO_MSEN;
+	tape_ccw_end(request->cpaddr, SENSE, 32, request->cpdata);
+	request->callback = (void *) __tape_34xx_medium_sense;
+	request->callback_data = NULL;
+	tape_do_io_async(device, request);
 }
 
 struct tape_34xx_work {
···
  * is inserted but cannot call tape_do_io* from an interrupt context.
  * Maybe that's useful for other actions we want to start from the
  * interrupt handler.
+ * Note: the work handler is called by the system work queue. The tape
+ * commands started by the handler need to be asynchrounous, otherwise
+ * a deadlock can occur e.g. in case of a deferred cc=1 (see __tape_do_irq).
  */
 static void
 tape_34xx_work_handler(struct work_struct *work)
···
 
 	switch(p->op) {
 		case TO_MSEN:
-			tape_34xx_medium_sense(device);
+			tape_34xx_medium_sense_async(device);
 			break;
 		default:
 			DBF_EVENT(3, "T34XX: internal error: unknown work\n");

drivers/s390/char/tape_3590.c

···
 /*
  * Enable encryption
  */
-static int tape_3592_enable_crypt(struct tape_device *device)
+static struct tape_request *__tape_3592_enable_crypt(struct tape_device *device)
 {
 	struct tape_request *request;
 	char *data;
 
 	DBF_EVENT(6, "tape_3592_enable_crypt\n");
 	if (!crypt_supported(device))
-		return -ENOSYS;
+		return ERR_PTR(-ENOSYS);
 	request = tape_alloc_request(2, 72);
 	if (IS_ERR(request))
-		return PTR_ERR(request);
+		return request;
 	data = request->cpdata;
 	memset(data,0,72);
 
···
 	request->op = TO_CRYPT_ON;
 	tape_ccw_cc(request->cpaddr, MODE_SET_CB, 36, data);
 	tape_ccw_end(request->cpaddr + 1, MODE_SET_CB, 36, data + 36);
+	return request;
+}
+
+static int tape_3592_enable_crypt(struct tape_device *device)
+{
+	struct tape_request *request;
+
+	request = __tape_3592_enable_crypt(device);
+	if (IS_ERR(request))
+		return PTR_ERR(request);
 	return tape_do_io_free(device, request);
+}
+
+static void tape_3592_enable_crypt_async(struct tape_device *device)
+{
+	struct tape_request *request;
+
+	request = __tape_3592_enable_crypt(device);
+	if (!IS_ERR(request))
+		tape_do_io_async_free(device, request);
 }
 
 /*
  * Disable encryption
  */
-static int tape_3592_disable_crypt(struct tape_device *device)
+static struct tape_request *__tape_3592_disable_crypt(struct tape_device *device)
 {
 	struct tape_request *request;
 	char *data;
 
 	DBF_EVENT(6, "tape_3592_disable_crypt\n");
 	if (!crypt_supported(device))
-		return -ENOSYS;
+		return ERR_PTR(-ENOSYS);
 	request = tape_alloc_request(2, 72);
 	if (IS_ERR(request))
-		return PTR_ERR(request);
+		return request;
 	data = request->cpdata;
 	memset(data,0,72);
 
···
 	tape_ccw_cc(request->cpaddr, MODE_SET_CB, 36, data);
 	tape_ccw_end(request->cpaddr + 1, MODE_SET_CB, 36, data + 36);
 
+	return request;
+}
+
+static int tape_3592_disable_crypt(struct tape_device *device)
+{
+	struct tape_request *request;
+
+	request = __tape_3592_disable_crypt(device);
+	if (IS_ERR(request))
+		return PTR_ERR(request);
 	return tape_do_io_free(device, request);
+}
+
+static void tape_3592_disable_crypt_async(struct tape_device *device)
+{
+	struct tape_request *request;
+
+	request = __tape_3592_disable_crypt(device);
+	if (!IS_ERR(request))
+		tape_do_io_async_free(device, request);
 }
 
 /*
···
 /*
  * SENSE Medium: Get Sense data about medium state
  */
-static int
-tape_3590_sense_medium(struct tape_device *device)
+static int tape_3590_sense_medium(struct tape_device *device)
 {
 	struct tape_request *request;
 
···
 	request->op = TO_MSEN;
 	tape_ccw_end(request->cpaddr, MEDIUM_SENSE, 128, request->cpdata);
 	return tape_do_io_free(device, request);
+}
+
+static void tape_3590_sense_medium_async(struct tape_device *device)
+{
+	struct tape_request *request;
+
+	request = tape_alloc_request(1, 128);
+	if (IS_ERR(request))
+		return;
+	request->op = TO_MSEN;
+	tape_ccw_end(request->cpaddr, MEDIUM_SENSE, 128, request->cpdata);
+	tape_do_io_async_free(device, request);
 }
 
 /*
···
  * 2. The attention msg is written to the "read subsystem data" buffer.
  * In this case we probably should print it to the console.
  */
-static int
-tape_3590_read_attmsg(struct tape_device *device)
+static void tape_3590_read_attmsg_async(struct tape_device *device)
 {
 	struct tape_request *request;
 	char *buf;
 
 	request = tape_alloc_request(3, 4096);
 	if (IS_ERR(request))
-		return PTR_ERR(request);
+		return;
 	request->op = TO_READ_ATTMSG;
 	buf = request->cpdata;
 	buf[0] = PREP_RD_SS_DATA;
···
 	tape_ccw_cc(request->cpaddr, PERFORM_SS_FUNC, 12, buf);
 	tape_ccw_cc(request->cpaddr + 1, READ_SS_DATA, 4096 - 12, buf + 12);
 	tape_ccw_end(request->cpaddr + 2, NOP, 0, NULL);
-	return tape_do_io_free(device, request);
+	tape_do_io_async_free(device, request);
 }
 
 /*
  * These functions are used to schedule follow-up actions from within an
  * interrupt context (like unsolicited interrupts).
+ * Note: the work handler is called by the system work queue. The tape
+ * commands started by the handler need to be asynchrounous, otherwise
+ * a deadlock can occur e.g. in case of a deferred cc=1 (see __tape_do_irq).
  */
 struct work_handler_data {
 	struct tape_device *device;
···
 
 	switch (p->op) {
 	case TO_MSEN:
-		tape_3590_sense_medium(p->device);
+		tape_3590_sense_medium_async(p->device);
 		break;
 	case TO_READ_ATTMSG:
-		tape_3590_read_attmsg(p->device);
+		tape_3590_read_attmsg_async(p->device);
 		break;
 	case TO_CRYPT_ON:
-		tape_3592_enable_crypt(p->device);
+		tape_3592_enable_crypt_async(p->device);
 		break;
 	case TO_CRYPT_OFF:
-		tape_3592_disable_crypt(p->device);
+		tape_3592_disable_crypt_async(p->device);
 		break;
 	default:
 		DBF_EVENT(3, "T3590: work handler undefined for "