On Thu, 2009-02-19 at 16:17 +0100, Nick Piggin wrote: > On Thu, Feb 19, 2009 at 09:49:40AM -0500, Kristian Høgsberg wrote: > > > > > Secondly, mmap_sem is not a recursive lock (very few kernel locks are, > > > and we generally frown upon recursive locking schemes), this means that > > > the fault handler still cannot function properly. > > > > I understand, but we take it twice only as a read lock, so that should > > work, right? We prevent the deadlock the lockdep validator warned about > > and as far as I can see, the patch doesn't introduce a new one. But > > other than that I agree with the frowning on recursive locking, it's too > > often used to paper over badly thought out locking. > > It doesn't work. rwsems are fair (otherwise there is terrible starvation > properties), so if another process does an interleaved down_write, then > the 2nd down_read will block until the down_write is serviced.
Ooh, right, yes of course, ouch. thanks, Kristian ------------------------------------------------------------------------------ Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise -Strategies to boost innovation and cut costs with open source participation -Receive a $600 discount off the registration fee with the source code: SFAD http://p.sf.net/sfu/XcvMzF8H -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
