Messages in this thread | | | Subject | Re: 2.6.17-rc6-mm1/pktcdvd - BUG: possible circular locking | From | Peter Osterlund <> | Date | 22 Jun 2006 16:50:28 +0200 |
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Arjan van de Ven <arjan@linux.intel.com> writes:
> Laurent Riffard wrote: > > Hello, > > This BUG happened while pktcdvd service was starting. Basically, the > > 2 following commands were issued: > > - modprobe ptkcdvd > > - pktsetup dvd /dev/dvd > > This appears to be a real bug: > > A normal pkt dvd block dev open takes the > bdev_mutex in the regular block device open path, which takes > ctl_mutex in the pkt_open function which gets called then from > the block layer. > > HOWEVER the IOCTL path does it the other way around: > > mutex_lock(&ctl_mutex); > ret = pkt_setup_dev(&ctrl_cmd); > mutex_unlock(&ctl_mutex); > > where pkt_setup_dev in term calls pkt_new_dev which > calls blkdev_get(), which takes the bdev_mutex. > > Looks very much like a AB-BA deadlock to me...
I don't understand how this could deadlock. If the device is already setup, pkt_new_dev() returns before calling blkdev_get(). If the device is not already setup, the block device doesn't exist yet so there can not be another caller in the pkt_open() path.
-- Peter Osterlund - petero2@telia.com http://web.telia.com/~u89404340 - 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/
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