Messages in this thread | | | Subject | Re: 2.6.17-rc6-mm1/pktcdvd - BUG: possible circular locking | From | Arjan van de Ven <> | Date | Fri, 14 Jul 2006 15:46:10 +0200 |
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On Fri, 2006-07-14 at 13:22 +0200, Peter Osterlund wrote: > > and what locking prevents this? And via multiple opens? > > You are right that my reasoning was incorrect. If someone is doing > "pktsetup ; pktsetup -d" quickly in a loop while someone else is > trying to open the device, one thread could be at the start of > pkt_open() at the same time as another thread is in pkt_new_dev(). > > However, I added a 5s delay in pkt_open() to enlarge the race window. > I still couldn't make the driver lock up though. The explanation is > that pkt_new_dev() calls blkdev_get() with the CD device (eg /dev/hdc) > as bdev parameter, while do_open() locks the bd_mutex for the pktcdvd > device (eg /dev/pktcdvd/0). > > Do you still think this could deadlock? If not, how should the code be > annotated to make this warning go away?
unless we KNOW it won't deadlock (eg we have a "this cannot deadlock BECAUSE of X, Y and Z") I don't think annotations are the right idea. In addition, the "how to annotate" really depends on what X, Y and Z are....
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