[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>

1 files changed, 67 insertions, 16 deletions

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
  */
-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);
 
@@ -383,9 +402,28 @@ static int tape_3592_disable_crypt(struct tape_device *device)
         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);
+}
+
 /*
  * IOCTL: Set encryption status
  */
@@ -457,8 +495,7 @@ tape_3590_ioctl(struct tape_device *device, unsigned int cmd, unsigned long arg)
 /*
  * 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;
 
@@ -470,6 +507,18 @@ tape_3590_sense_medium(struct tape_device *device)
         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);
+}
+
 /*
  * MTTELL: Tell block. Return the number of block relative to current file.
  */
@@ -546,15 +595,14 @@ tape_3590_read_opposite(struct tape_device *device,
  * 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;
@@ -562,12 +610,15 @@ tape_3590_read_attmsg(struct tape_device *device)
         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;
@@ -583,16 +634,16 @@ tape_3590_work_handler(struct work_struct *work)
 
         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 "