MFC 287833:

Threads holding a read lock of a sleepable rm lock are not permitted
to sleep.  The rmlock implementation enforces this by disabling
sleeping when a read lock is acquired. To simplify the implementation,
sleeping is disabled for most of the duration of rm_rlock.  However,
it doesn't need to be disabled until the lock is acquired.  If a
sleepable rm lock is contested, then rm_rlock may need to acquire the
backing sx lock.  This tripped the overly-broad assertion.  Fix by
relaxing the assertion around the call to sx_xlock().

1 files changed, 4 insertions, 2 deletions

diff --git a/sys/kern/kern_rmlock.c b/sys/kern/kern_rmlock.c
index 1ac08de..194c603 100644
--- a/sys/kern/kern_rmlock.c
+++ b/sys/kern/kern_rmlock.c
@@ -402,9 +402,11 @@ _rm_rlock_hard(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
 				return (0);
 		}
 	} else {
-		if (rm->lock_object.lo_flags & LO_SLEEPABLE)
+		if (rm->lock_object.lo_flags & LO_SLEEPABLE) {
+			THREAD_SLEEPING_OK();
 			sx_xlock(&rm->rm_lock_sx);
-		else
+			THREAD_NO_SLEEPING();
+		} else
 			mtx_lock(&rm->rm_lock_mtx);
 	}