It's not really feasible to do deadlock detection with FL_FILE_PVT
locks since they aren't owned by a single task, per-se. Deadlock
detection also tends to be rather expensive so just skip it for
these sorts of locks.
Also, add a FIXME comment about adding more limited deadlock detection
that just applies to ro -> rw upgrades, per Andy's request.
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/locks.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index f8cd6d7de161..8c5bc07c360f 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -564,7 +564,7 @@ static void __locks_insert_block(struct file_lock *blocker,
BUG_ON(!list_empty(&waiter->fl_block));
waiter->fl_next = blocker;
list_add_tail(&waiter->fl_block, &blocker->fl_block);
- if (IS_POSIX(blocker))
+ if (IS_POSIX(blocker) && !IS_FILE_PVT(blocker))
locks_insert_global_blocked(waiter);
}
@@ -757,8 +757,16 @@ EXPORT_SYMBOL(posix_test_lock);
* Note: the above assumption may not be true when handling lock
* requests from a broken NFS client. It may also fail in the presence
* of tasks (such as posix threads) sharing the same open file table.
- *
* To handle those cases, we just bail out after a few iterations.
+ *
+ * For FL_FILE_PVT locks, the owner is the filp, not the files_struct.
+ * Because the owner is not even nominally tied to a thread of
+ * execution, the deadlock detection below can't reasonably work well. Just
+ * skip it for those.
+ *
+ * In principle, we could do a more limited deadlock detection on FL_FILE_PVT
+ * locks that just checks for the case where two tasks are attempting to
+ * upgrade from read to write locks on the same inode.
*/
#define MAX_DEADLK_ITERATIONS 10
@@ -781,6 +789,13 @@ static int posix_locks_deadlock(struct file_lock *caller_fl,
{
int i = 0;
+ /*
+ * This deadlock detector can't reasonably detect deadlocks with
+ * FL_FILE_PVT locks, since they aren't owned by a process, per-se.
+ */
+ if (IS_FILE_PVT(caller_fl))
+ return 0;
+
while ((block_fl = what_owner_is_waiting_for(block_fl))) {
if (i++ > MAX_DEADLK_ITERATIONS)
return 0;
--
1.8.5.3
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
