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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>
This commit is contained in:
Finn Thain 2016-01-03 16:05:38 +11:00 committed by Martin K. Petersen
parent 8d8601a757
commit 010e89d18c
2 changed files with 6 additions and 75 deletions
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1
drivers/scsi/NCR5380.h
View File

@ -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

80
drivers/scsi/atari_NCR5380.c
View File

@ -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);
}