src/patches/suse-2.6.27.25/patches.arch/s390-11-13-zfcp_avoid_semaphore_race.patch

   1 From: Gerald Schaefer <geraldsc@de.ibm.com>
   2 Subject: zfcp: avoid false ERP complete task due to semaphore race.
   3 References: bnc#484767,LTC#55250
   4
   5 Symptom:     The adapter is not able to perform an initial exchange config.
   6 Problem:     The ERP thread is performing a task before it is executing the
   7              corresponding down on the semaphore. The response handler of the
   8              just started exchange config should wait for the completion by
   9              performing a down on this semaphore. Since this semaphore is still
  10              positive from the ERP enqueue the handler won't wait and therefore
  11              the exchange config will always fail leaving the adapter in error.
  12 Solution:    Perform the down on the semaphore before starting an ERP task.
  13              This is the logically correct order. Only walk the ERP loop
  14              if there is a task to perform.
  15
  16 Acked-by: John Jolly <jjolly@suse.de>
  17
  18 ---
  19  drivers/s390/scsi/zfcp_erp.c |   10 ++++++----
  20  1 file changed, 6 insertions(+), 4 deletions(-)
  21
  22 Index: linux-sles11/drivers/s390/scsi/zfcp_erp.c
  23 ===================================================================
  24 --- linux-sles11.orig/drivers/s390/scsi/zfcp_erp.c
  25 +++ linux-sles11/drivers/s390/scsi/zfcp_erp.c
  26 @@ -1310,6 +1310,7 @@ static int zfcp_erp_thread(void *data)
  27         struct list_head *next;
  28         struct zfcp_erp_action *act;
  29         unsigned long flags;
  30 +       int ignore;
  31
  32         daemonize("zfcperp%s", adapter->ccw_device->dev.bus_id);
  33         /* Block all signals */
  34 @@ -1319,6 +1320,11 @@ static int zfcp_erp_thread(void *data)
  35
  36         while (!(atomic_read(&adapter->status) &
  37                  ZFCP_STATUS_ADAPTER_ERP_THREAD_KILL)) {
  38 +
  39 +               zfcp_rec_dbf_event_thread_lock(4, adapter);
  40 +               ignore = down_interruptible(&adapter->erp_ready_sem);
  41 +               zfcp_rec_dbf_event_thread_lock(5, adapter);
  42 +
  43                 write_lock_irqsave(&adapter->erp_lock, flags);
  44                 next = adapter->erp_ready_head.next;
  45                 write_unlock_irqrestore(&adapter->erp_lock, flags);
  46 @@ -1330,10 +1336,6 @@ static int zfcp_erp_thread(void *data)
  47                         if (zfcp_erp_strategy(act) != ZFCP_ERP_DISMISSED)
  48                                 zfcp_erp_wakeup(adapter);
  49                 }
  50 -
  51 -               zfcp_rec_dbf_event_thread_lock(4, adapter);
  52 -               down_interruptible(&adapter->erp_ready_sem);
  53 -               zfcp_rec_dbf_event_thread_lock(5, adapter);
  54         }
  55
  56         atomic_clear_mask(ZFCP_STATUS_ADAPTER_ERP_THREAD_UP, &adapter->status);