The patch titled
rtmutex: Remove buggy BUG_ON in PI boosting code
has been removed from the -mm tree. Its filename is
rtmutex-remove-buggy-bug_on-in-pi-boosting-code.patch
This patch was probably dropped from -mm because
it has now been merged into a subsystem tree or
into Linus's tree, or because it was folded into
its parent patch in the -mm tree.
------------------------------------------------------
Subject: rtmutex: Remove buggy BUG_ON in PI boosting code
From: Steven Rostedt <rostedt@xxxxxxxxxxx>
The condition in that particular BUG_ON can legitimately be the
case, if you have processes A, B, C, D, and E holding the
following locks in this scenario:
L1 <=blocks= A
<=owns= L2 <=blocks= B <=owns= L4 <=blocks= D
<=owns= L3 <=blocks= C <=owns= L5 <=blocks= E
Where the priorities of these tasks are
B,C < A < D = E
B and C are less than A and A is less than D and E where D and E are
equal (actually it probably works when D and E are not equal too).
As D and E climb the chain, there's a very slight race condition that
could allow for the condition in the offending BUG_ON to be true.
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/rtmutex.c | 4 +---
1 files changed, 1 insertion(+), 3 deletions(-)
diff -puN kernel/rtmutex.c~rtmutex-remove-buggy-bug_on-in-pi-boosting-code kernel/rtmutex.c
--- devel/kernel/rtmutex.c~rtmutex-remove-buggy-bug_on-in-pi-boosting-code 2006-05-11 15:19:30.000000000 -0700
+++ devel-akpm/kernel/rtmutex.c 2006-05-11 15:19:30.000000000 -0700
@@ -212,10 +212,8 @@ static int rt_mutex_adjust_prio_chain(ta
* When deadlock detection is off then we check, if further
* priority adjustment is necessary.
*/
- if (!detect_deadlock && waiter->list_entry.prio == task->prio) {
- BUG_ON(waiter->pi_list_entry.prio != waiter->list_entry.prio);
+ if (!detect_deadlock && waiter->list_entry.prio == task->prio)
goto out_unlock_pi;
- }
lock = waiter->lock;
if (!spin_trylock(&lock->wait_lock)) {
_
Patches currently in -mm which might be from rostedt@xxxxxxxxxxx are
fix-for-serial-uart-lockup.patch
jbd-avoid-kfree-null.patch
ext3_clear_inode-avoid-kfree-null.patch
sched-comment-bitmap-size-accounting.patch
unnecessary-long-index-i-in-sched.patch
pi-futex-rt-mutex-docspatch.patch
rtmutex-remove-buggy-bug_on-in-pi-boosting-code.patch
document-futex-pi-design.patch
document-futex-pi-design-fix.patch
document-futex-pi-design-fix-fix.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
