Messages in this thread Patch in this message | | | Subject | PATCH (for comment): ide-cd possible race in PIO mode | From | Alan Cox <> | Date | Wed, 17 Nov 2004 13:19:50 +0000 |
| |
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); } } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |