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author | Thomas Gleixner <tglx@linutronix.de> | 2010-01-20 20:59:06 +0000 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2010-01-22 18:09:59 +0100 |
commit | 60db48cacb9b253d5607a5ff206112a59cd09e34 (patch) | |
tree | 7fc9be93263ae40381cdafe3cb31c4521e88f2dd /kernel | |
parent | 37dad3fce97f01e5149d69de0833d8452c0e862e (diff) | |
download | kernel_samsung_tuna-60db48cacb9b253d5607a5ff206112a59cd09e34.zip kernel_samsung_tuna-60db48cacb9b253d5607a5ff206112a59cd09e34.tar.gz kernel_samsung_tuna-60db48cacb9b253d5607a5ff206112a59cd09e34.tar.bz2 |
sched: Queue a deboosted task to the head of the RT prio queue
rtmutex_set_prio() is used to implement priority inheritance for
futexes. When a task is deboosted it gets enqueued at the tail of its
RT priority list. This is violating the POSIX scheduling semantics:
rt priority list X contains two runnable tasks A and B
task A runs with priority X and holds mutex M
task C preempts A and is blocked on mutex M
-> task A is boosted to priority of task C (Y)
task A unlocks the mutex M and deboosts itself
-> A is dequeued from rt priority list Y
-> A is enqueued to the tail of rt priority list X
task C schedules away
task B runs
This is wrong as task A did not schedule away and therefor violates
the POSIX scheduling semantics.
Enqueue the task to the head of the priority list instead.
Reported-by: Mathias Weber <mathias.weber.mw1@roche.com>
Reported-by: Carsten Emde <cbe@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Carsten Emde <cbe@osadl.org>
Tested-by: Mathias Weber <mathias.weber.mw1@roche.com>
LKML-Reference: <20100120171629.809074113@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index f47560f..a56ead4 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4237,7 +4237,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio) if (running) p->sched_class->set_curr_task(rq); if (on_rq) { - enqueue_task(rq, p, 0, false); + enqueue_task(rq, p, 0, oldprio < prio); check_class_changed(rq, p, prev_class, oldprio, running); } |