[PATCH] zfcp: fix incorrect usage of fsf_req_list_lock

  =================================
  [ INFO: inconsistent lock state ]
  ---------------------------------
  inconsistent {in-hardirq-W} -> {hardirq-on-W} usage.
  swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
   (&adapter->fsf_req_list_lock){++..}, at: [<0000000000274486>] zfcp_qdio_reqid_check+0x46/0x178
  {in-hardirq-W} state was registered at:
    [<000000000005fb0c>] __lock_acquire+0xad8/0xed0
    [<00000000000604ae>] lock_acquire+0x9a/0xc8
    [<000000000035a326>] _spin_lock+0x4e/0x68
    [<0000000000274486>] zfcp_qdio_reqid_check+0x46/0x178
    [<000000000027469e>] zfcp_qdio_response_handler+0xe6/0x430
    [<0000000000219dd4>] tiqdio_thinint_handler+0xd20/0x213c
    [<000000000020229a>] do_adapter_IO+0xb2/0xc0
    [<0000000000206f32>] do_IRQ+0x136/0x16c
    [<0000000000020462>] io_no_vtime+0x16/0x1c
    [<0000000000019432>] cpu_idle+0x222/0x250
  irq event stamp: 129220
  hardirqs last  enabled at (129220): [<00000000000411e6>] tasklet_hi_action+0x5a/0x19c
  hardirqs last disabled at (129219): [<00000000000411c0>] tasklet_hi_action+0x34/0x19c
  softirqs last  enabled at (129212): [<0000000000040b62>] __do_softirq+0x13a/0x180
  softirqs last disabled at (129217): [<000000000001fd58>] do_softirq+0xec/0xf0

  other info that might help us debug this:
  no locks held by swapper/0.

  stack backtrace:
  00000000012bb670 0000000000000002 0000000000000000 00000000012bb780
         00000000012bb6e8 0000000000399122 0000000000399122 0000000000016b0a
         0000000000000000 0000000000000000 0000000000000000 00000000004660e8
         0000000000000000 000000000000000d 00000000012bb6e0 00000000012bb758
         0000000000368b90 0000000000016b0a 00000000012bb6e0 00000000012bb730
  Call Trace:
  ([<0000000000016a26>] show_trace+0x76/0xdc)
   [<0000000000016b2c>] show_stack+0xa0/0xd0
   [<0000000000016b8a>] dump_stack+0x2e/0x3c
   [<000000000005e3da>] print_usage_bug+0x27e/0x290
   [<000000000005ea9c>] mark_lock+0x6b0/0x6c0
   [<000000000005f33e>] __lock_acquire+0x30a/0xed0
   [<00000000000604ae>] lock_acquire+0x9a/0xc8
   [<000000000035a326>] _spin_lock+0x4e/0x68
   [<0000000000274486>] zfcp_qdio_reqid_check+0x46/0x178
   [<000000000027469e>] zfcp_qdio_response_handler+0xe6/0x430
   [<0000000000217bd2>] tiqdio_tl+0xd02/0x2120
   [<000000000004123a>] tasklet_hi_action+0xae/0x19c
   [<0000000000040ae4>] __do_softirq+0xbc/0x180
   [<000000000001fd58>] do_softirq+0xec/0xf0
   [<0000000000040c38>] irq_exit+0x90/0xa8
   [<0000000000206f40>] do_IRQ+0x144/0x16c
   [<0000000000020462>] io_no_vtime+0x16/0x1c
   [<0000000000019432>] cpu_idle+0x222/0x250
  ([<0000000000019416>] cpu_idle+0x206/0x250)
   [<000000000001405a>] rest_init+0x5a/0x68
   [<0000000000536998>] start_kernel+0x39c/0x3dc
   [<0000000000013046>] _stext+0x46/0x1000

Fix incorrect usage of fsf_req_list_lock. It's used in tasklet context
(irqs on) as well as in irq context. Therefore use the spin_lock_irqsave
variant to avoid deadlocks.
Acked-by: NAndreas Herrmann <aherrman@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/s390/scsi/zfcp_qdio.c

@@ -427,6 +427,7 @@ int
 zfcp_qdio_reqid_check(struct zfcp_adapter *adapter, void *sbale_addr)
 {
 	struct zfcp_fsf_req *fsf_req;
+	unsigned long flags;
 
 	/* invalid (per convention used in this driver) */
 	if (unlikely(!sbale_addr)) {
@@ -438,15 +439,15 @@ zfcp_qdio_reqid_check(struct zfcp_adapter *adapter, void *sbale_addr)
 	fsf_req = (struct zfcp_fsf_req *) sbale_addr;
 
 	/* serialize with zfcp_fsf_req_dismiss_all */
-	spin_lock(&adapter->fsf_req_list_lock);
+	spin_lock_irqsave(&adapter->fsf_req_list_lock, flags);
 	if (list_empty(&adapter->fsf_req_list_head)) {
-		spin_unlock(&adapter->fsf_req_list_lock);
+		spin_unlock_irqrestore(&adapter->fsf_req_list_lock, flags);
 		return 0;
 	}
 	list_del(&fsf_req->list);
 	atomic_dec(&adapter->fsf_reqs_active);
-	spin_unlock(&adapter->fsf_req_list_lock);
-	
+	spin_unlock_irqrestore(&adapter->fsf_req_list_lock, flags);
+
 	if (unlikely(adapter != fsf_req->adapter)) {
 		ZFCP_LOG_NORMAL("bug: invalid reqid (fsf_req=%p, "
 				"fsf_req->adapter=%p, adapter=%p)\n",