atari_scsi: Fix atari_scsi deadlocks on Falcon

Don't disable irqs when waiting for the ST DMA "lock"; its release may
require an interrupt.

Introduce stdma_try_lock() for use in soft irq context. atari_scsi now tells
the SCSI mid-layer to defer queueing a command if the ST DMA lock is not
available, as per Michael's patch:
http://marc.info/?l=linux-m68k&m=139095335824863&w=2

The falcon_got_lock variable is race prone: we can't disable IRQs while
waiting to acquire the lock, so after acquiring it there must be some
interval during which falcon_got_lock remains false. Introduce
stdma_is_locked_by() to replace falcon_got_lock.

The falcon_got_lock tests in the EH handlers are incorrect these days. It
can happen that an EH handler is called after a command completes normally.
Remove these checks along with falcon_got_lock.

Also remove the complicated and racy fairness wait queues. If fairness is an
issue (when SCSI competes with IDE for the ST DMA interrupt), the solution
is likely to be a lower value for host->can_queue.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/m68k/include/asm/atari_stdma.h b/arch/m68k/include/asm/atari_stdma.h
index 8e389b7fa70c..d24e34d870dc 100644
--- a/arch/m68k/include/asm/atari_stdma.h
+++ b/arch/m68k/include/asm/atari_stdma.h
@@ -8,11 +8,11 @@
 
 /***************************** Prototypes *****************************/
 
+int stdma_try_lock(irq_handler_t, void *);
 void stdma_lock(irq_handler_t handler, void *data);
 void stdma_release( void );
-int stdma_others_waiting( void );
 int stdma_islocked( void );
-void *stdma_locked_by( void );
+int stdma_is_locked_by(irq_handler_t);
 void stdma_init( void );
 
 /************************* End of Prototypes **************************/