+++ This bug was initially created as a clone of Bug #456686 +++ Description of problem: There is a missing memory barrier in the current aio_complete in the RHEL5 kernels causing a race between read_events/aio_complete causing the thread in read_events to sleep indefinitely, hanging the application that is waiting on I/O completion. This was reported upstream by Quentin Barnes of Yahoo: http://lkml.org/lkml/2008/3/12/207 Fix has been merged in 2.6.26: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=6cb2a21049b8990df4576c5fce4d48d0206c22d5 And was also accepted for 2.6.24.y: http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.24.y.git;a=commit;h=0db49fc729eee503836ea12745b55f7f802d2abb Version-Release number of selected component (if applicable): How reproducible: Unclear. Depends on the AIO application; Quentin reports seeing hangs virtually 100% of the time. Looking for a straightforward reproducer for this now and will update with details when they are available. Steps to Reproduce: < to be filled > Actual results: Application hangs in read_events Expected results: No hang. AIO completes as normal. Additional info: