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Subject[PATCH] fs/locks.c: Fix posix locking for threaded tasks

Saurabh Desai believes that locks created by threads should not conflict
with each other. I'm inclined to agree; I don't know why the test for
->fl_pid was added, but the comment suggests that whoever added it wasn't
sure either.

Frankly, I have no clue about the intended semantics for threads, and
SUS v3 does not offer any enlightenment. But it seems reasonable that
processes which share a files_struct should share locks. After all,
if one process closes the fd, they'll remove locks belonging to the
other process.

Here's a patch generated against 2.4; it also applies to 2.5.
Please apply.

===== fs/locks.c 1.9 vs edited =====
--- 1.9/fs/locks.c Mon Jun 3 18:49:43 2002
+++ edited/fs/locks.c Fri Jun 7 21:24:12 2002
@@ -380,15 +380,12 @@
}

/*
- * Check whether two locks have the same owner
- * N.B. Do we need the test on PID as well as owner?
- * (Clone tasks should be considered as one "owner".)
+ * Locks are deemed to have the same owner if the tasks share files_struct.
*/
static inline int
locks_same_owner(struct file_lock *fl1, struct file_lock *fl2)
{
- return (fl1->fl_owner == fl2->fl_owner) &&
- (fl1->fl_pid == fl2->fl_pid);
+ return (fl1->fl_owner == fl2->fl_owner);
}

/* Remove waiter from blocker's block list.
--
Revolutions do not require corporate support.
-
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