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authorPeter Zijlstra <peterz@infradead.org>2013-11-07 14:43:43 +0100
committerIngo Molnar <mingo@kernel.org>2014-01-13 13:41:50 +0100
commitfb00aca474405f4fa8a8519c3179fed722eabd83 (patch)
tree8a779629a771dd3340d5a3ba0ba16b732b8de1c8 /kernel/fork.c
parentaf6ace764d03900524e9b1ac621a1c520ee49fc6 (diff)
rtmutex: Turn the plist into an rb-tree
Turn the pi-chains from plist to rb-tree, in the rt_mutex code, and provide a proper comparison function for -deadline and -priority tasks. This is done mainly because: - classical prio field of the plist is just an int, which might not be enough for representing a deadline; - manipulating such a list would become O(nr_deadline_tasks), which might be to much, as the number of -deadline task increases. Therefore, an rb-tree is used, and tasks are queued in it according to the following logic: - among two -priority (i.e., SCHED_BATCH/OTHER/RR/FIFO) tasks, the one with the higher (lower, actually!) prio wins; - among a -priority and a -deadline task, the latter always wins; - among two -deadline tasks, the one with the earliest deadline wins. Queueing and dequeueing functions are changed accordingly, for both the list of a task's pi-waiters and the list of tasks blocked on a pi-lock. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Dario Faggioli <raistlin@linux.it> Signed-off-by: Juri Lelli <juri.lelli@gmail.com> Signed-off-again-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1383831828-15501-10-git-send-email-juri.lelli@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index e6c0f1a22914..7049ae526a54 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1087,7 +1087,8 @@ static void rt_mutex_init_task(struct task_struct *p)
{
raw_spin_lock_init(&p->pi_lock);
#ifdef CONFIG_RT_MUTEXES
- plist_head_init(&p->pi_waiters);
+ p->pi_waiters = RB_ROOT;
+ p->pi_waiters_leftmost = NULL;
p->pi_blocked_on = NULL;
#endif
}