linux-kernel - [PATCH, RFC 02/30] scsi: atari_scsi: fix sleep

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Date:	Thu,  2 Jan 2014 13:07:26 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-kernel@...r.kernel.org
Cc:	Arnd Bergmann <arnd@...db.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	linux-scsi@...r.kernel.org
Subject: [PATCH, RFC 02/30] scsi: atari_scsi: fix sleep_on race

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@...db.de>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: James E.J. Bottomley <JBottomley@...allels.com>
Cc: linux-scsi@...r.kernel.org
---
 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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