Messages in this thread | | | Date | Sun, 23 Jul 2006 17:58:49 +0100 (BST) | Subject | Re: [patch 3/3] [-rt] Fixes the timeout-bug in the rtmutex/PI-futex. | From | Esben Nielsen <> |
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On Sun, 23 Jul 2006, Steven Rostedt wrote:
> On Sun, 2006-07-23 at 02:18 +0100, Esben Nielsen wrote: >> This patch fixes >> >> 1) The timeout bug in rtmutexes and PI futexes: When a task is blocked on a >> lock with timeout and times out it will not wakeup until the owner of the lock >> is done. This is because the owner is boosted to the same priority as the >> blocked task and therefore has the CPU such the blocked task never gets around >> to de-boost it! >> >> 2) setscheduler() now does the PI walking - but defers the work to the blocked >> task. >> >> 3) In general it makes sure that a task, which is boosting another has enough >> priority to do the de-boosting no matter how complicated the lock structure is, >> or how many times the priorities have changed. >> >> The idea behind the patch is simple: >> If a task is boosting another it is scheduled in LIFO order and it will never >> loose it's priority. This property lasts until it has left the lock operation >> (successfully or not). >> >> The needed priority to do the unboosting is stored in task->boosting_prio. >> In the current patch this is always increasing (numerically decreasing) while >> trying to take a lock. In a future it might be found safe to decrease >> boosting_prio before finally leaving the lock operation. >> >> include/linux/rtmutex.h | 1 >> include/linux/sched.h | 7 >> kernel/fork.c | 1 >> kernel/rtmutex.c | 151 +++++++++++++----- > > It is possible that these changes can break the pi code in rtmutex.c.
Hmm, I am quite confident this one doesn't :-) It is tested against my own user-space unit tester and against Thomas's in-kernel rt-tester. And my stress PriorityInheritanceTest by the way.
> I > haven't analyzed it enough yet. But just so that you know that your > changes don't break the code, and to make it easier for me to look at > it. Please update Documentation/rt-mutex-design.txt including your > changes. This will be a good exercise to see if it doesn't really break > anything, and it will give other reviewers a better starting point for > review.
Is that up-to-date in the -rt tree? The last patch you sent was to 2.6.18-rc2, right?
Esben
> >> kernel/rtmutex_common.h | 1 >> kernel/sched.c | 14 + >> scripts/rt-tester/t5-l4-pi-boost-deboost-setsched.tst | 42 +++-- >> scripts/rt-tester/t5-l4-pi-boost-deboost.tst | 12 - >> 8 files changed, 167 insertions(+), 62 deletions(-) > > -- Steve > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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