ncr5380: Standardize work queueing algorithm

The complex main_running/queue_main mechanism is peculiar to
atari_NCR5380.c. It isn't SMP safe and offers little value given that
the work queue already offers concurrency management. Remove this
complexity to bring atari_NCR5380.c closer to NCR5380.c.

It is not a good idea to call the information transfer state machine from
queuecommand because, according to Documentation/scsi/scsi_mid_low_api.txt
that could happen in soft irq context. Fix this.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/NCR5380.h b/drivers/scsi/NCR5380.h
index 7ffcb0c33a225db766523147f4fa74d040c04a90..78af75142342ff390a540fb97d067f2a4ac95300 100644 (file)
--- a/drivers/scsi/NCR5380.h
+++ b/drivers/scsi/NCR5380.h
@@ -262,7 +262,6 @@ struct NCR5380_hostdata {
                                           * transfer to handle chip overruns */
        int retain_dma_intr;
        struct work_struct main_task;
-       volatile int main_running;
 #ifdef SUPPORT_TAGS
        struct tag_alloc TagAlloc[8][8];        /* 8 targets and 8 LUNs */
 #endif

diff --git a/drivers/scsi/atari_NCR5380.c b/drivers/scsi/atari_NCR5380.c
index 437e1e59b905f6e986ff6330c49d1c0a0a9da6b3..48e3d76e39e3d1942b143fb014ddec7fd24211e3 100644 (file)
--- a/drivers/scsi/atari_NCR5380.c
+++ b/drivers/scsi/atari_NCR5380.c
@@ -602,36 +602,6 @@ static void NCR5380_print_phase(struct Scsi_Host *instance)
 
 #endif
 
-/*
- * ++roman: New scheme of calling NCR5380_main()
- *
- * If we're not in an interrupt, we can call our main directly, it cannot be
- * already running. Else, we queue it on a task queue, if not 'main_running'
- * tells us that a lower level is already executing it. This way,
- * 'main_running' needs not be protected in a special way.
- *
- * queue_main() is a utility function for putting our main onto the task
- * queue, if main_running is false. It should be called only from a
- * interrupt or bottom half.
- */
-
-#include <linux/gfp.h>
-#include <linux/workqueue.h>
-#include <linux/interrupt.h>
-
-static inline void queue_main(struct NCR5380_hostdata *hostdata)
-{
-       if (!hostdata->main_running) {
-               /* If in interrupt and NCR5380_main() not already running,
-                  queue it on the 'immediate' task queue, to be processed
-                  immediately after the current interrupt processing has
-                  finished. */
-               queue_work(hostdata->work_q, &hostdata->main_task);
-       }
-       /* else: nothing to do: the running NCR5380_main() will pick up
-          any newly queued command. */
-}
-
 /**
  * NCR58380_info - report driver and host information
  * @instance: relevant scsi host instance
@@ -714,8 +684,6 @@ static void __maybe_unused NCR5380_print_status(struct Scsi_Host *instance)
        hostdata = (struct NCR5380_hostdata *)instance->hostdata;
 
        local_irq_save(flags);
-       printk("NCR5380: coroutine is%s running.\n",
-               hostdata->main_running ? "" : "n't");
        if (!hostdata->connected)
                printk("scsi%d: no currently connected command\n", HOSTNO);
        else
@@ -757,8 +725,6 @@ static int __maybe_unused NCR5380_show_info(struct seq_file *m,
        hostdata = (struct NCR5380_hostdata *)instance->hostdata;
 
        local_irq_save(flags);
-       seq_printf(m, "NCR5380: coroutine is%s running.\n",
-               hostdata->main_running ? "" : "n't");
        if (!hostdata->connected)
                seq_printf(m, "scsi%d: no currently connected command\n", HOSTNO);
        else
@@ -997,17 +963,8 @@ static int NCR5380_queue_command(struct Scsi_Host *instance,
        dprintk(NDEBUG_QUEUES, "scsi%d: command added to %s of queue\n", H_NO(cmd),
                  (cmd->cmnd[0] == REQUEST_SENSE) ? "head" : "tail");
 
-       /* If queue_command() is called from an interrupt (real one or bottom
-        * half), we let queue_main() do the job of taking care about main. If it
-        * is already running, this is a no-op, else main will be queued.
-        *
-        * If we're not in an interrupt, we can call NCR5380_main()
-        * unconditionally, because it cannot be already running.
-        */
-       if (in_interrupt() || irqs_disabled())
-               queue_main(hostdata);
-       else
-               NCR5380_main(&hostdata->main_task);
+       /* Kick off command processing */
+       queue_work(hostdata->work_q, &hostdata->main_task);
        return 0;
 }
 
@@ -1044,30 +1001,11 @@ static void NCR5380_main(struct work_struct *work)
        unsigned long flags;
 
        /*
-        * We run (with interrupts disabled) until we're sure that none of
-        * the host adapters have anything that can be done, at which point
-        * we set main_running to 0 and exit.
-        *
-        * Interrupts are enabled before doing various other internal
-        * instructions, after we've decided that we need to run through
-        * the loop again.
-        *
-        * this should prevent any race conditions.
-        *
         * ++roman: Just disabling the NCR interrupt isn't sufficient here,
         * because also a timer int can trigger an abort or reset, which can
         * alter queues and touch the Falcon lock.
         */
 
-       /* Tell int handlers main() is now already executing.  Note that
-          no races are possible here. If an int comes in before
-          'main_running' is set here, and queues/executes main via the
-          task queue, it doesn't do any harm, just this instance of main
-          won't find any work left to do. */
-       if (hostdata->main_running)
-               return;
-       hostdata->main_running = 1;
-
        local_save_flags(flags);
        do {
                local_irq_disable();    /* Freeze request queues */
@@ -1182,11 +1120,6 @@ static void NCR5380_main(struct work_struct *work)
                        done = 0;
                }
        } while (!done);
-
-       /* Better allow ints _after_ 'main_running' has been cleared, else
-          an interrupt could believe we'll pick up the work it left for
-          us, but we won't see it anymore here... */
-       hostdata->main_running = 0;
        local_irq_restore(flags);
 }
 
@@ -1299,6 +1232,7 @@ static void NCR5380_dma_complete(struct Scsi_Host *instance)
 static irqreturn_t NCR5380_intr(int irq, void *dev_id)
 {
        struct Scsi_Host *instance = dev_id;
+       struct NCR5380_hostdata *hostdata = shost_priv(instance);
        int done = 1, handled = 0;
        unsigned char basr;
 
@@ -1367,11 +1301,9 @@ static irqreturn_t NCR5380_intr(int irq, void *dev_id)
 #endif
        }
 
-       if (!done) {
-               dprintk(NDEBUG_INTR, "scsi%d: in int routine, calling main\n", HOSTNO);
-               /* Put a call to NCR5380_main() on the queue... */
-               queue_main(shost_priv(instance));
-       }
+       if (!done)
+               queue_work(hostdata->work_q, &hostdata->main_task);
+
        return IRQ_RETVAL(handled);
 }