[ofa-general] Application blocked in mthca_poll_cq

[Roland Dreier]

 > I am not sure about the version of OFED being used, but its most likely
 > OFED-1.2. Is there any way to find the version of OFED used. libmthca.so
 > points to libmthca-rdmav2.so. I am not sure if this helps. My application is
 > multithreaded, every time this happens when I try to attach the process to
 > gdb I find that mthca_poll_cq is the one blocking and sometimes the call is
 > blocking on pthread_spin_unlock. Which is surprising as I wouldnt expect
 > pthread_spin_unlock to be blocking. I am sure that I am not doing any
 > use-after-free. I dont destroy the CQ till the application is terminating.
 > This situation occurs well before the application terminates.

Yes, it's not really possible for pthread_spin_unlock() to block.  In
general (on any common architecture -- 32/64-bit x86, powerpc, ia64 --
at least) pthread_spin_unlock() is just a single store to the spinlock
memory location.  What that says to me is that either gdb is giving
you bogus information (quite possible) or perhaps your application is
not really stuck -- it is just in a tight loop polling a CQ maybe?

(BTW I think you should be able to determine the libmthca version by
doing "rpm -qi libmthca")

 - R.