[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 <schwidefsky@de.ibm.com>

3 files changed, 116 insertions, 34 deletions

diff --git a/drivers/s390/char/tape.h b/drivers/s390/char/tape.h
index 7a242f073632..267b54e8ff5a 100644
--- a/drivers/s390/char/tape.h
+++ b/drivers/s390/char/tape.h
@@ -280,6 +280,14 @@ tape_do_io_free(struct tape_device *device, struct tape_request *request)
         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 *);
diff --git a/drivers/s390/char/tape_34xx.c b/drivers/s390/char/tape_34xx.c
index c17f35b6136a..c26511171ffe 100644
--- a/drivers/s390/char/tape_34xx.c
+++ b/drivers/s390/char/tape_34xx.c
@@ -53,23 +53,11 @@ static void tape_34xx_delete_sbid_from(struct tape_device *, int);
  * 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;
-
-        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);
+        struct tape_device *device = request->device;
+        unsigned char *sense;
 
-        rc = tape_do_io_interruptible(device, request);
         if (request->rc == 0) {
                 sense = request->cpdata;
 
@@ -88,15 +76,47 @@ tape_34xx_medium_sense(struct tape_device *device)
                         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 {
         struct tape_device      *device;
         enum tape_op             op;
@@ -109,6 +129,9 @@ 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)
@@ -119,7 +142,7 @@ 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");
diff --git a/drivers/s390/char/tape_3590.c b/drivers/s390/char/tape_3590.c
index fbe361fcd2c0..de2e99e0a71b 100644
--- a/drivers/s390/char/tape_3590.c
+++ b/drivers/s390/char/tape_3590.c
@@ -329,17 +329,17 @@ out:
 /*
  * 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);
 
@@ -354,23 +354,42 @@ static int tape_3592_enable_crypt(struct tape_device *device)
         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