From: Thomas Gleixner Date: Wed, 20 Jan 2010 20:59:06 +0000 (+0000) Subject: sched: Queue a deboosted task to the head of the RT prio queue X-Git-Tag: v2.6.34-rc1~260^2~11 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=60db48cacb9b253d5607a5ff206112a59cd09e34;p=pandora-kernel.git 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 Reported-by: Carsten Emde Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Tested-by: Carsten Emde Tested-by: Mathias Weber LKML-Reference: <20100120171629.809074113@linutronix.de> --- Reading git-diff-tree failed