src/patches/suse-2.6.27.39/patches.drivers/ibmvfc_tasklet.patch

   1 Subject: Fix dropped interrupts
   2 From: Brian King <brking@linux.vnet.ibm.com>
   3 References: 473115 - LTC51485
   4
   5 This patch fixes a problem of possible dropped interrupts. Currently, the ibmvfc
   6 driver has a race condition where after ibmvfc_interrupt gets run, the platform
   7 code clears the interrupt. This can result in lost interrupts and, in worst case
   8 scenarios, result in command timeouts. Fix this by implementing a tasklet
   9 similar to what the ibmvscsi driver does so that interrupt processing is no longer
  10 done in the actual interrupt handler, which eliminates the race.
  11
  12 Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
  13 Signed-off-by: Olaf Hering <olh@suse.de>
  14 ---
  15
  16  drivers/scsi/ibmvscsi/ibmvfc.c |   25 +++++++++++++++++++++++--
  17  drivers/scsi/ibmvscsi/ibmvfc.h |    1 +
  18  2 files changed, 24 insertions(+), 2 deletions(-)
  19
  20 --- a/drivers/scsi/ibmvscsi/ibmvfc.c
  21 +++ b/drivers/scsi/ibmvscsi/ibmvfc.c
  22 @@ -640,6 +640,7 @@ static void ibmvfc_release_crq_queue(str
  23
  24         ibmvfc_dbg(vhost, "Releasing CRQ\n");
  25         free_irq(vdev->irq, vhost);
  26 +       tasklet_kill(&vhost->tasklet);
  27         do {
  28                 rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
  29         } while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
  30 @@ -2697,6 +2698,25 @@ static struct ibmvfc_crq *ibmvfc_next_cr
  31  static irqreturn_t ibmvfc_interrupt(int irq, void *dev_instance)
  32  {
  33         struct ibmvfc_host *vhost = (struct ibmvfc_host *)dev_instance;
  34 +       unsigned long flags;
  35 +
  36 +       spin_lock_irqsave(vhost->host->host_lock, flags);
  37 +       vio_disable_interrupts(to_vio_dev(vhost->dev));
  38 +       tasklet_schedule(&vhost->tasklet);
  39 +       spin_unlock_irqrestore(vhost->host->host_lock, flags);
  40 +       return IRQ_HANDLED;
  41 +}
  42 +
  43 +/**
  44 + * ibmvfc_tasklet - Interrupt handler tasklet
  45 + * @data:              ibmvfc host struct
  46 + *
  47 + * Returns:
  48 + *     Nothing
  49 + **/
  50 +static void ibmvfc_tasklet(void *data)
  51 +{
  52 +       struct ibmvfc_host *vhost = data;
  53         struct vio_dev *vdev = to_vio_dev(vhost->dev);
  54         struct ibmvfc_crq *crq;
  55         struct ibmvfc_async_crq *async;
  56 @@ -2704,7 +2724,6 @@ static irqreturn_t ibmvfc_interrupt(int
  57         int done = 0;
  58
  59         spin_lock_irqsave(vhost->host->host_lock, flags);
  60 -       vio_disable_interrupts(to_vio_dev(vhost->dev));
  61         while (!done) {
  62                 /* Pull all the valid messages off the CRQ */
  63                 while ((crq = ibmvfc_next_crq(vhost)) != NULL) {
  64 @@ -2732,7 +2751,6 @@ static irqreturn_t ibmvfc_interrupt(int
  65         }
  66
  67         spin_unlock_irqrestore(vhost->host->host_lock, flags);
  68 -       return IRQ_HANDLED;
  69  }
  70
  71  /**
  72 @@ -3857,6 +3875,8 @@ static int ibmvfc_init_crq(struct ibmvfc
  73
  74         retrc = 0;
  75
  76 +       tasklet_init(&vhost->tasklet, (void *)ibmvfc_tasklet, (unsigned long)vhost);
  77 +
  78         if ((rc = request_irq(vdev->irq, ibmvfc_interrupt, 0, IBMVFC_NAME, vhost))) {
  79                 dev_err(dev, "Couldn't register irq 0x%x. rc=%d\n", vdev->irq, rc);
  80                 goto req_irq_failed;
  81 @@ -3872,6 +3892,7 @@ static int ibmvfc_init_crq(struct ibmvfc
  82         return retrc;
  83
  84  req_irq_failed:
  85 +       tasklet_kill(&vhost->tasklet);
  86         do {
  87                 rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
  88         } while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
  89 --- a/drivers/scsi/ibmvscsi/ibmvfc.h
  90 +++ b/drivers/scsi/ibmvscsi/ibmvfc.h
  91 @@ -684,6 +684,7 @@ struct ibmvfc_host {
  92         char partition_name[97];
  93         void (*job_step) (struct ibmvfc_host *);
  94         struct task_struct *work_thread;
  95 +       struct tasklet_struct tasklet;
  96         wait_queue_head_t init_wait_q;
  97         wait_queue_head_t work_wait_q;
  98  };