IB/hfi1: Remove critical section gap in sc_buffer_alloc()

In sc_buffer_alloc(), the sc->alloc_lock is released
before calling sc_release_update(), and it is reacquired
after the function call. This causes CPU lock trading.
Fix it by not dropping the lock before calling
sc_release_update().
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Sebastian Sanchez <sebastian.sanchez@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/hfi1/pio.c

@@ -1419,9 +1419,7 @@ struct pio_buf *sc_buffer_alloc(struct send_context *sc, u32 dw_len,
 			(sc->fill - sc->alloc_free);
 		if (blocks > avail) {
 			/* still no room, actively update */
-			spin_unlock_irqrestore(&sc->alloc_lock, flags);
 			sc_release_update(sc);
-			spin_lock_irqsave(&sc->alloc_lock, flags);
 			sc->alloc_free = ACCESS_ONCE(sc->free);
 			trycount++;
 			goto retry;