[PATCH] scsi/atari_scsi: Fix race condition between .queuecommand and EH

From: Finn Thain
Date: Thu Nov 19 2020 - 23:52:06 EST


It is possible that bus_reset_cleanup() or .eh_abort_handler could
be invoked during NCR5380_queuecommand(). If that takes place before
the new command is enqueued and after the ST-DMA "lock" has been
acquired, the ST-DMA "lock" will be released again. This will result
in a lost DMA interrupt and a command timeout. Fix this by excluding
EH and interrupt handlers while the new command is enqueued.

Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
---
Michael, would you please send your Acked-by or Reviewed-and-tested-by?
These two patches taken together should be equivalent to the one you tested
recently. I've split it into two as that seemed to make more sense.
---
drivers/scsi/NCR5380.c | 9 ++++++---
drivers/scsi/atari_scsi.c | 10 +++-------
2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
index d654a6cc4162..ea4b5749e7da 100644
--- a/drivers/scsi/NCR5380.c
+++ b/drivers/scsi/NCR5380.c
@@ -580,11 +580,14 @@ static int NCR5380_queue_command(struct Scsi_Host *instance,

cmd->result = 0;

- if (!NCR5380_acquire_dma_irq(instance))
- return SCSI_MLQUEUE_HOST_BUSY;
-
spin_lock_irqsave(&hostdata->lock, flags);

+ if (!NCR5380_acquire_dma_irq(instance)) {
+ spin_unlock_irqrestore(&hostdata->lock, flags);
+
+ return SCSI_MLQUEUE_HOST_BUSY;
+ }
+
/*
* Insert the cmd into the issue queue. Note that REQUEST SENSE
* commands are added to the head of the queue since any command will
diff --git a/drivers/scsi/atari_scsi.c b/drivers/scsi/atari_scsi.c
index a82b63a66635..95d7a3586083 100644
--- a/drivers/scsi/atari_scsi.c
+++ b/drivers/scsi/atari_scsi.c
@@ -376,15 +376,11 @@ static int falcon_get_lock(struct Scsi_Host *instance)
if (IS_A_TT())
return 1;

- if (stdma_is_locked_by(scsi_falcon_intr) &&
- instance->hostt->can_queue > 1)
+ if (stdma_is_locked_by(scsi_falcon_intr))
return 1;

- if (in_interrupt())
- return stdma_try_lock(scsi_falcon_intr, instance);
-
- stdma_lock(scsi_falcon_intr, instance);
- return 1;
+ /* stdma_lock() may sleep which means it can't be used here */
+ return stdma_try_lock(scsi_falcon_intr, instance);
}

#ifndef MODULE
--
2.26.2