PATCH (for comment): ide-cd possible race in PIO mode

[Alan Cox]

Working on tracing down Fedora bug #115458
(https://bugzilla.redhat.com/bugzilla/process_bug.cgi) I found what
appears to be a race between the IDE CD driver and the hardware status.
It doesn't appear to explain the bug at all but it does look like a bug
of itself

When we issue an ide command the status bits don't become valid for
400nS. In the DMA case ide_execute_command handles this but in the PIO
case we don't do the needed locking, use OUTBSYNC to avoid posting or
delay. This means that in some situations we can execute the command
handler in PIO mode before the command status bits are valid and the
handler may read and act wrongly.

--- drivers/ide/ide-cd.c~	2004-11-17 14:08:42.950485320 +0000
+++ drivers/ide/ide-cd.c	2004-11-17 14:08:42.951485168 +0000
@@ -897,7 +897,10 @@
 		return ide_started;
 	} else {
 		/* packet command */
-		HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
+		spin_lock_irqsave(&ide_lock, flags);
+		HWIF(drive)->OUTBSYNC(WIN_PACKETCMD, IDE_COMMAND_REG);
+		ndelay(400);
+		spin_unlock_irqsave(&ide_lock, flags);
 		return (*handler) (drive);
 	}
 }

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