Messages in this thread | | | Date | Sun, 1 Oct 2006 13:36:31 +0200 (CEST) | From | Esben Nielsen <> | Subject | [patch 0/5] Fix timeout bug in rtmutex in 2.6.18-rt |
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Hi, I finally got around to merge my patches into a newer -rt kernel and repost them.
To refresh: pthread_mutex_timedlock() for PI-futexes doesn't work on a UP machine: Task A tries to take a lock with a timeout of say 1 ms. This lock is owned by B which is boosted to task A's priority. The timeout interrupt wakes up A, but since B is already running at A's priority, A will not get any CPU before B unlocks the lock anyway.
This series of patches does the following:
1) It adds an interface to the scheduler such that task A is woken up LIFO instead of FIFO. That means that A is now preempting B even though they have the same priority. Thus A can de-boost B and exit the pthread_mutex_timedlock() before B is done with the lock.
2) This is a smaller update to the rt-mutex-tester scripts. Probably not needed, I'll post it anyway.
3) This patch makes sure that A will not loose it's priority while boosting B. In case of other PI-mutex operations touches A's priority or explicit setscheduler() calls, A will not actually loose it's priority. That is postponed until A leaves the lock operation (successfully or not). Thus A will always be able to de-boost B.
4) Is a documentation update.
5) Is a fix to the PI-futex: There is (still) lacking a protection for the rtmutex's internal state because. It might not be the cleanest way to do this.
Esben
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