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rtmutex: Turn the plist into an rb-tree

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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>
This commit is contained in:
Peter Zijlstra
2013-11-07 14:43:43 +01:00
committed by Ingo Molnar
parent af6ace764d
commit fb00aca474
9 changed files with 157 additions and 65 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
kernel/locking/rtmutex_common.h
View File

@@ -40,13 +40,13 @@ extern void schedule_rt_mutex_test(struct rt_mutex *lock);
* This is the control structure for tasks blocked on a rt_mutex,
* which is allocated on the kernel stack on of the blocked task.
*
* @list_entry: pi node to enqueue into the mutex waiters list
* @pi_list_entry: pi node to enqueue into the mutex owner waiters list
* @tree_entry: pi node to enqueue into the mutex waiters tree
* @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
* @task: task reference to the blocked task
*/
struct rt_mutex_waiter {
struct plist_node list_entry;
struct plist_node pi_list_entry;
struct rb_node tree_entry;
struct rb_node pi_tree_entry;
struct task_struct *task;
struct rt_mutex *lock;
#ifdef CONFIG_DEBUG_RT_MUTEXES
@@ -57,11 +57,11 @@ struct rt_mutex_waiter {
};
/*
* Various helpers to access the waiters-plist:
* Various helpers to access the waiters-tree:
*/
static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
{
return !plist_head_empty(&lock->wait_list);
return !RB_EMPTY_ROOT(&lock->waiters);
}
static inline struct rt_mutex_waiter *
@@ -69,8 +69,8 @@ rt_mutex_top_waiter(struct rt_mutex *lock)
{
struct rt_mutex_waiter *w;
w = plist_first_entry(&lock->wait_list, struct rt_mutex_waiter,
list_entry);
w = rb_entry(lock->waiters_leftmost, struct rt_mutex_waiter,
tree_entry);
BUG_ON(w->lock != lock);
return w;
@@ -78,14 +78,14 @@ rt_mutex_top_waiter(struct rt_mutex *lock)
static inline int task_has_pi_waiters(struct task_struct *p)
{
return !plist_head_empty(&p->pi_waiters);
return !RB_EMPTY_ROOT(&p->pi_waiters);
}
static inline struct rt_mutex_waiter *
task_top_pi_waiter(struct task_struct *p)
{
return plist_first_entry(&p->pi_waiters, struct rt_mutex_waiter,
pi_list_entry);
return rb_entry(p->pi_waiters_leftmost, struct rt_mutex_waiter,
pi_tree_entry);
}
/*