On Sun, 28 Oct 2007 12:27:32 -0600 Matthew Wilcox <matthew@xxxxxx> wrote: > On Sun, Oct 28, 2007 at 01:43:21PM -0400, J. Bruce Fields wrote: > > We currently attempt to return -EDEALK to blocking fcntl() file locking > > requests that would create a cycle in the graph of tasks waiting on > > locks. > > > > This is inefficient: in the general case it requires us determining > > whether we're adding a cycle to an arbitrary directed acyclic graph. > > And this calculation has to be performed while holding a lock (currently > > the BKL) that prevents that graph from changing. > > > > It has historically been a source of bugs; most recently it was noticed > > that it could loop indefinitely while holding the BKL. > > It can also return -EDEADLK spuriously. So yeah, just kill it. NAK. This is an ABI change. It was also comprehensively rejected before because - EDEADLK behaviour is ABI - EDEADLK behaviour is required by SuSv3 - We have no idea what applications may rely on this behaviour. and also SuSv3 is required by LSB See the thread http://osdir.com/ml/file-systems/2004-06/msg00017.html so we need to fix the bugs - the lock usage and the looping. At that point it merely becomes a performance concern to those who use it, which is the proper behaviour. If you want a faster non-checking one use flock(), or add another flag that is a Linux "don't check for deadlock" Alan - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
