Arnd,
your patch breaks the Atari NCR5380 SCSI driver (easily verified using
ARAnyM). Last console output:
scsi0: options CAN_QUEUE=8 CMD_PER_LUN=1 SCAT-GAT=0 TAGGED-QUEUING=no
HOSTID=7 generic options AUTOSENSE REAL DMA SCSI-2 TAGGED QUEUING
generic release=7
scsi0 : Atari native SCSI
blk_queue_max_segments: set to minimum 1
scsi0: aborting command
scsi 0:0:0:0: CDB:
Inquiry: 12 00 00 00 24 00
NCR5380 core release=7.
NCR5380: coroutine isn't running.
scsi0: no currently connected command
scsi0: issue_queue
scsi0: disconnected_queue
random: nonblocking pool is initialized
scsi0: !!BINGO!! Falcon has no lock in NCR5380_abort
scsi0: warning : SCSI command probably completed successfully before
abortion
No targets are connected, so the driver is expected to time out and
abort each INQUIRY command. This works fine with the unmodified version
of the driver (even though its locking scheme is well beyond crazy - I
grant you that much). Note that the unmodified version also works fine
on my actual Falcon hardware under moderate load (meaning to say, no
hardware instabilities are triggered that would cause the SCSI chip to
lock up and require a bus reset).
I'll debug this a bit to see where it gets stuck. Thanks for looking
into this ugly mess of code!
Cheers,
Michael
Michael Schmitz wrote:
Geert,
thanks for passing that on - I had in fact disabled that feature of
the driver for a good part of the 3.x series of kernels while
attempting to figure out what else is wrong with the locking scheme.
I'll take a fresh stab at this.
Cheers,
Michael
Am 03.01.2014 um 01:26 schrieb Geert Uytterhoeven:
---------- Forwarded message ----------
From: Arnd Bergmann <arnd@xxxxxxxx>
Date: Thu, Jan 2, 2014 at 1:07 PM
Subject: [PATCH, RFC 02/30] scsi: atari_scsi: fix sleep_on race
To: linux-kernel@xxxxxxxxxxxxxxx
Cc: Arnd Bergmann <arnd@xxxxxxxx>, Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx>, "James E.J. Bottomley"
<JBottomley@xxxxxxxxxxxxx>, linux-scsi@xxxxxxxxxxxxxxx
sleep_on is known broken and going away. The atari_scsi driver is one of
two remaining users in the falcon_get_lock() function, which is a rather
crazy piece of code. This does not attempt to fix the driver's locking
scheme in general, but at least prevents falcon_get_lock from going to
sleep when no other thread holds the same lock or tries to get it,
and we no longer schedule with irqs disabled.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: James E.J. Bottomley <JBottomley@xxxxxxxxxxxxx>
Cc: linux-scsi@xxxxxxxxxxxxxxx
---
drivers/scsi/atari_scsi.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/atari_scsi.c b/drivers/scsi/atari_scsi.c
index a3e6c8a..b55a58a 100644
--- a/drivers/scsi/atari_scsi.c
+++ b/drivers/scsi/atari_scsi.c
@@ -90,6 +90,7 @@
#include <linux/init.h>
#include <linux/nvram.h>
#include <linux/bitops.h>
+#include <linux/wait.h>
#include <asm/setup.h>
#include <asm/atarihw.h>
@@ -549,8 +550,10 @@ static void falcon_get_lock(void)
local_irq_save(flags);
- while (!in_irq() && falcon_got_lock && stdma_others_waiting())
- sleep_on(&falcon_fairness_wait);
+ wait_event_cmd(falcon_fairness_wait,
+ !in_irq() && falcon_got_lock &&
stdma_others_waiting(),
+ local_irq_restore(flags),
+ local_irq_save(flags));
while (!falcon_got_lock) {
if (in_irq())
@@ -562,7 +565,10 @@ static void falcon_get_lock(void)
falcon_trying_lock = 0;
wake_up(&falcon_try_wait);
} else {
- sleep_on(&falcon_try_wait);
+ wait_event_cmd(falcon_try_wait,
+ !falcon_got_lock &&
!falcon_trying_lock,
+ local_irq_restore(flags),
+ local_irq_save(flags));
}
}
--
1.8.3.2
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