On Mon, 2007-09-17 at 08:56 -0700, Roland Dreier wrote: > > When using OFED-1.2.5 based infiniband kernel modules on 2.6.22 based > > kernels with the Ingo Molnar CONFIG_PREEMPT_RT applied, then commands > > such as ibnetdiscvoer, smpquery, sminfo, etc. will hang. The problem > > is with the downgrade_write() rw semaphore usage in the > > ib_umad_close() routine. > > Can you give a few more details on how PREEMPT_RT changes locking > rules (or just exposes existing bugs maybe?) so that the > downgrade_write() causes the issue? I would like to fix this cleanly > but I don't really understand what the problem is. the read/write semaphore functionality is basically reduced to just a binary semaphore , i.e. one reader, or one writer . I think the BUG(); in downgrade_write() is likely part of a removal plan for downgrade_write() (that's just a guess tho) Daniel - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
