Simplify rwlock implementation.

Remove RW_COUNT() from the rwlock implementation.  The idea was that it
could be used as a generic wrapper for getting at the internal state
of a rwlock.  While a good idea it's proven problematic to keep it
correct for multiple archs and internal implementation changes.  In
short it hasn't been worth the trouble.

With that and simplicity in mind things have been updated to use the
rwsem_is_locked() function instead of RW_COUNT for the RW_*_HELD()
functions.  As for rw_upgrade() it remains only implemented for
the generic rwsem implemenation.  It remains to be determined if its
worth the effort of adding a custom implementation for each arch.

1 files changed, 12 insertions, 4 deletions

diff --git a/module/splat/splat-rwlock.c b/module/splat/splat-rwlock.c
index 6b2ecbe82..dc560c2b9 100644
--- a/module/splat/splat-rwlock.c
+++ b/module/splat/splat-rwlock.c
@@ -571,7 +571,7 @@ static int
 splat_rwlock_test6(struct file *file, void *arg)
 {
 	rw_priv_t *rwp;
-	int rc = -EINVAL;
+	int rc;
 
 	rwp = (rw_priv_t *)kmalloc(sizeof(*rwp), GFP_KERNEL);
 	if (rwp == NULL)
@@ -584,15 +584,18 @@ splat_rwlock_test6(struct file *file, void *arg)
 		splat_vprint(file, SPLAT_RWLOCK_TEST6_NAME,
 		             "rwlock should be read lock: %d\n",
 			     RW_READ_HELD(&rwp->rw_rwlock));
+		rc = -ENOLCK;
 		goto out;
 	}
 
-	/* With one reader upgrade should never fail */
+#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
+	/* With one reader upgrade should never fail. */
 	rc = rw_tryupgrade(&rwp->rw_rwlock);
 	if (!rc) {
 		splat_vprint(file, SPLAT_RWLOCK_TEST6_NAME,
-			     "rwlock contended preventing upgrade: %ld\n",
-			     (long int)RW_COUNT(&rwp->rw_rwlock));
+			     "rwlock failed upgrade from reader: %d\n",
+			     RW_READ_HELD(&rwp->rw_rwlock));
+		rc = -ENOLCK;
 		goto out;
 	}
 
@@ -607,6 +610,11 @@ splat_rwlock_test6(struct file *file, void *arg)
 	rc = 0;
 	splat_vprint(file, SPLAT_RWLOCK_TEST6_NAME, "%s",
 		     "rwlock properly upgraded\n");
+#else
+	rc = 0;
+	splat_vprint(file, SPLAT_RWLOCK_TEST6_NAME, "%s",
+		     "rw_tryupgrade() is disabled for this arch\n");
+#endif
 out:
 	rw_exit(&rwp->rw_rwlock);
 	rw_destroy(&rwp->rw_rwlock);