Hi Guys,
I finally found the bug(s) causing these hangs. The first problem was
in the request scheduler, with the new crdirent pass-through changes.
The handle the crdirent gets queued on is actually the directory handle
instead of the dirent handle, so the operation on that handle is
technically read-only. Treating it as modifying was causing other
operations that came along (setattr, for example) to get queued instead
of scheduled.
That was the first cause of hangs. The second was in the way the sync
coalescing code worked. There were cases where operations were getting
queued as ready-to-be-synced (coalesced), but the following operations
that got serviced were failing (appropriately with EEXISTS), and never
calling any of the coalescing code. Julian and I had talked about this
being a problem a while back, but I guess it never got looked at. In
any case, I was able to cleanup the sync coalescing code some, so it was
probably worth it.
The tests of doing multiple simultaneous creates and unlinks to the same
file seem to work fine now, including the open test in test/posix. Let
me know if any of you still have problems.
Thanks,
-sam
Murali Vilayannur wrote:
Hi RobL,
I'm seeing this on chiba with posix ior and the flash io benchmark
(oddly enough, just with the parallel netcdf version, not the hdf5
one).
I agree it's something related to chiba, but have no idea what it
could be. I tried a different version of berkely db and saw the same
results.
pvfs2-ping works, but pvfs2-ls hangs in getattr. servers don't
*appear* to be stuck in anything, but I only hooked up a debugger to
the server-that-wouldn't-die.
I really wish we could rule this as a Chiba-specific bug, since it is so
hard to reproduce elsewhere or we would have known by now! :)
Since, I was using the vfs interface and not the mpi-io interface,
I can only think of the simultaneous create and unlink being the issue
here.
The other possibility is a bug in the aio libraries on Chiba...
If any one has any insights or seen similar behavior, do let us know!
thanks,
Murali
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