From: Steven Rostedt 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 Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton --- 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)) { _