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>
This commit is contained in:
Peter Zijlstra
Ingo Molnar
parent
af6ace764d
commit
fb00aca474
9 changed files with 157 additions and 65 deletions
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@ -11,6 +11,7 @@
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#include <linux/user_namespace.h>
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#include <linux/securebits.h>
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#include <linux/seqlock.h>
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#include <linux/rbtree.h>
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#include <net/net_namespace.h>
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#include <linux/sched/rt.h>
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@ -154,6 +155,14 @@ extern struct task_group root_task_group;
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#define INIT_TASK_COMM "swapper"
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#ifdef CONFIG_RT_MUTEXES
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# define INIT_RT_MUTEXES(tsk) \
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.pi_waiters = RB_ROOT, \
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.pi_waiters_leftmost = NULL,
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#else
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# define INIT_RT_MUTEXES(tsk)
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#endif
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/*
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* INIT_TASK is used to set up the first task table, touch at
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* your own risk!. Base=0, limit=0x1fffff (=2MB)
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@ -221,6 +230,7 @@ extern struct task_group root_task_group;
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INIT_TRACE_RECURSION \
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INIT_TASK_RCU_PREEMPT(tsk) \
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INIT_CPUSET_SEQ(tsk) \
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INIT_RT_MUTEXES(tsk) \
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INIT_VTIME(tsk) \
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}
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@ -13,7 +13,7 @@
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#define __LINUX_RT_MUTEX_H
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#include <linux/linkage.h>
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#include <linux/plist.h>
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#include <linux/rbtree.h>
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#include <linux/spinlock_types.h>
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extern int max_lock_depth; /* for sysctl */
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@ -22,12 +22,14 @@ extern int max_lock_depth; /* for sysctl */
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* The rt_mutex structure
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*
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* @wait_lock: spinlock to protect the structure
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* @wait_list: pilist head to enqueue waiters in priority order
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* @waiters: rbtree root to enqueue waiters in priority order
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* @waiters_leftmost: top waiter
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* @owner: the mutex owner
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*/
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struct rt_mutex {
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raw_spinlock_t wait_lock;
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struct plist_head wait_list;
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struct rb_root waiters;
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struct rb_node *waiters_leftmost;
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struct task_struct *owner;
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#ifdef CONFIG_DEBUG_RT_MUTEXES
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int save_state;
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@ -66,7 +68,7 @@ struct hrtimer_sleeper;
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#define __RT_MUTEX_INITIALIZER(mutexname) \
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{ .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(mutexname.wait_lock) \
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, .wait_list = PLIST_HEAD_INIT(mutexname.wait_list) \
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, .waiters = RB_ROOT \
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, .owner = NULL \
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__DEBUG_RT_MUTEX_INITIALIZER(mutexname)}
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@ -98,12 +100,4 @@ extern int rt_mutex_trylock(struct rt_mutex *lock);
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extern void rt_mutex_unlock(struct rt_mutex *lock);
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#ifdef CONFIG_RT_MUTEXES
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# define INIT_RT_MUTEXES(tsk) \
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.pi_waiters = PLIST_HEAD_INIT(tsk.pi_waiters), \
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INIT_RT_MUTEX_DEBUG(tsk)
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#else
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# define INIT_RT_MUTEXES(tsk)
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#endif
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#endif
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@ -16,6 +16,7 @@ struct sched_param {
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#include <linux/types.h>
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#include <linux/timex.h>
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#include <linux/jiffies.h>
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#include <linux/plist.h>
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#include <linux/rbtree.h>
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#include <linux/thread_info.h>
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#include <linux/cpumask.h>
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@ -1354,7 +1355,8 @@ struct task_struct {
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#ifdef CONFIG_RT_MUTEXES
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/* PI waiters blocked on a rt_mutex held by this task */
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struct plist_head pi_waiters;
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struct rb_root pi_waiters;
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struct rb_node *pi_waiters_leftmost;
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/* Deadlock detection and priority inheritance handling */
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struct rt_mutex_waiter *pi_blocked_on;
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#endif
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@ -1087,7 +1087,8 @@ static void rt_mutex_init_task(struct task_struct *p)
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{
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raw_spin_lock_init(&p->pi_lock);
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#ifdef CONFIG_RT_MUTEXES
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plist_head_init(&p->pi_waiters);
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p->pi_waiters = RB_ROOT;
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p->pi_waiters_leftmost = NULL;
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p->pi_blocked_on = NULL;
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#endif
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}
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@ -2316,6 +2316,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
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* code while we sleep on uaddr.
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*/
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debug_rt_mutex_init_waiter(&rt_waiter);
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RB_CLEAR_NODE(&rt_waiter.pi_tree_entry);
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RB_CLEAR_NODE(&rt_waiter.tree_entry);
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rt_waiter.task = NULL;
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ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
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@ -24,7 +24,7 @@
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#include <linux/kallsyms.h>
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#include <linux/syscalls.h>
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#include <linux/interrupt.h>
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#include <linux/plist.h>
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#include <linux/rbtree.h>
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#include <linux/fs.h>
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#include <linux/debug_locks.h>
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@ -57,7 +57,7 @@ static void printk_lock(struct rt_mutex *lock, int print_owner)
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void rt_mutex_debug_task_free(struct task_struct *task)
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{
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DEBUG_LOCKS_WARN_ON(!plist_head_empty(&task->pi_waiters));
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DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters));
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DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
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}
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@ -154,16 +154,12 @@ void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
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void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
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{
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memset(waiter, 0x11, sizeof(*waiter));
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plist_node_init(&waiter->list_entry, MAX_PRIO);
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plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
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waiter->deadlock_task_pid = NULL;
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}
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void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
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{
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put_pid(waiter->deadlock_task_pid);
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DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->list_entry));
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DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
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memset(waiter, 0x22, sizeof(*waiter));
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}
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@ -14,6 +14,7 @@
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#include <linux/export.h>
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#include <linux/sched.h>
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#include <linux/sched/rt.h>
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#include <linux/sched/deadline.h>
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#include <linux/timer.h>
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#include "rtmutex_common.h"
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@ -91,10 +92,104 @@ static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
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}
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#endif
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static inline int
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rt_mutex_waiter_less(struct rt_mutex_waiter *left,
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struct rt_mutex_waiter *right)
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{
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if (left->task->prio < right->task->prio)
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return 1;
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/*
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* If both tasks are dl_task(), we check their deadlines.
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*/
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if (dl_prio(left->task->prio) && dl_prio(right->task->prio))
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return (left->task->dl.deadline < right->task->dl.deadline);
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return 0;
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}
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static void
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rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
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{
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struct rb_node **link = &lock->waiters.rb_node;
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struct rb_node *parent = NULL;
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struct rt_mutex_waiter *entry;
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int leftmost = 1;
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while (*link) {
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parent = *link;
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entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry);
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if (rt_mutex_waiter_less(waiter, entry)) {
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link = &parent->rb_left;
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} else {
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link = &parent->rb_right;
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leftmost = 0;
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}
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}
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if (leftmost)
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lock->waiters_leftmost = &waiter->tree_entry;
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rb_link_node(&waiter->tree_entry, parent, link);
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rb_insert_color(&waiter->tree_entry, &lock->waiters);
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}
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static void
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rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
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{
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if (RB_EMPTY_NODE(&waiter->tree_entry))
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return;
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if (lock->waiters_leftmost == &waiter->tree_entry)
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lock->waiters_leftmost = rb_next(&waiter->tree_entry);
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rb_erase(&waiter->tree_entry, &lock->waiters);
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RB_CLEAR_NODE(&waiter->tree_entry);
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}
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static void
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rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
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{
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struct rb_node **link = &task->pi_waiters.rb_node;
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struct rb_node *parent = NULL;
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struct rt_mutex_waiter *entry;
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int leftmost = 1;
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while (*link) {
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parent = *link;
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entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry);
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if (rt_mutex_waiter_less(waiter, entry)) {
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link = &parent->rb_left;
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} else {
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link = &parent->rb_right;
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leftmost = 0;
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}
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}
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if (leftmost)
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task->pi_waiters_leftmost = &waiter->pi_tree_entry;
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rb_link_node(&waiter->pi_tree_entry, parent, link);
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rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters);
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}
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static void
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rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
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{
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if (RB_EMPTY_NODE(&waiter->pi_tree_entry))
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return;
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if (task->pi_waiters_leftmost == &waiter->pi_tree_entry)
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task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry);
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rb_erase(&waiter->pi_tree_entry, &task->pi_waiters);
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RB_CLEAR_NODE(&waiter->pi_tree_entry);
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}
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/*
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* Calculate task priority from the waiter list priority
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* Calculate task priority from the waiter tree priority
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*
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* Return task->normal_prio when the waiter list is empty or when
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* Return task->normal_prio when the waiter tree is empty or when
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* the waiter is not allowed to do priority boosting
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*/
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int rt_mutex_getprio(struct task_struct *task)
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@ -102,7 +197,7 @@ int rt_mutex_getprio(struct task_struct *task)
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if (likely(!task_has_pi_waiters(task)))
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return task->normal_prio;
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return min(task_top_pi_waiter(task)->pi_list_entry.prio,
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return min(task_top_pi_waiter(task)->task->prio,
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task->normal_prio);
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}
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@ -233,7 +328,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
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* When deadlock detection is off then we check, if further
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* priority adjustment is necessary.
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*/
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if (!detect_deadlock && waiter->list_entry.prio == task->prio)
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if (!detect_deadlock && waiter->task->prio == task->prio)
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goto out_unlock_pi;
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lock = waiter->lock;
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@ -254,9 +349,9 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
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top_waiter = rt_mutex_top_waiter(lock);
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/* Requeue the waiter */
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plist_del(&waiter->list_entry, &lock->wait_list);
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waiter->list_entry.prio = task->prio;
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plist_add(&waiter->list_entry, &lock->wait_list);
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rt_mutex_dequeue(lock, waiter);
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waiter->task->prio = task->prio;
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rt_mutex_enqueue(lock, waiter);
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/* Release the task */
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raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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@ -280,17 +375,15 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
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if (waiter == rt_mutex_top_waiter(lock)) {
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/* Boost the owner */
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plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
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waiter->pi_list_entry.prio = waiter->list_entry.prio;
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plist_add(&waiter->pi_list_entry, &task->pi_waiters);
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rt_mutex_dequeue_pi(task, top_waiter);
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rt_mutex_enqueue_pi(task, waiter);
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__rt_mutex_adjust_prio(task);
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} else if (top_waiter == waiter) {
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/* Deboost the owner */
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plist_del(&waiter->pi_list_entry, &task->pi_waiters);
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rt_mutex_dequeue_pi(task, waiter);
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waiter = rt_mutex_top_waiter(lock);
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waiter->pi_list_entry.prio = waiter->list_entry.prio;
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plist_add(&waiter->pi_list_entry, &task->pi_waiters);
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rt_mutex_enqueue_pi(task, waiter);
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__rt_mutex_adjust_prio(task);
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}
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@ -355,7 +448,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
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* 3) it is top waiter
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*/
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if (rt_mutex_has_waiters(lock)) {
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if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) {
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if (task->prio >= rt_mutex_top_waiter(lock)->task->prio) {
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if (!waiter || waiter != rt_mutex_top_waiter(lock))
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return 0;
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}
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@ -369,7 +462,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
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/* remove the queued waiter. */
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if (waiter) {
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plist_del(&waiter->list_entry, &lock->wait_list);
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rt_mutex_dequeue(lock, waiter);
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task->pi_blocked_on = NULL;
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}
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@ -379,8 +472,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
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*/
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if (rt_mutex_has_waiters(lock)) {
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top = rt_mutex_top_waiter(lock);
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top->pi_list_entry.prio = top->list_entry.prio;
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plist_add(&top->pi_list_entry, &task->pi_waiters);
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rt_mutex_enqueue_pi(task, top);
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}
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raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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}
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@ -416,13 +508,11 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
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__rt_mutex_adjust_prio(task);
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waiter->task = task;
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waiter->lock = lock;
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plist_node_init(&waiter->list_entry, task->prio);
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plist_node_init(&waiter->pi_list_entry, task->prio);
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/* Get the top priority waiter on the lock */
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if (rt_mutex_has_waiters(lock))
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top_waiter = rt_mutex_top_waiter(lock);
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plist_add(&waiter->list_entry, &lock->wait_list);
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rt_mutex_enqueue(lock, waiter);
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task->pi_blocked_on = waiter;
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@ -433,8 +523,8 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
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if (waiter == rt_mutex_top_waiter(lock)) {
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raw_spin_lock_irqsave(&owner->pi_lock, flags);
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plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
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plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
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rt_mutex_dequeue_pi(owner, top_waiter);
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rt_mutex_enqueue_pi(owner, waiter);
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__rt_mutex_adjust_prio(owner);
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if (owner->pi_blocked_on)
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@ -486,7 +576,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock)
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* boosted mode and go back to normal after releasing
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* lock->wait_lock.
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*/
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plist_del(&waiter->pi_list_entry, ¤t->pi_waiters);
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rt_mutex_dequeue_pi(current, waiter);
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rt_mutex_set_owner(lock, NULL);
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@ -510,7 +600,7 @@ static void remove_waiter(struct rt_mutex *lock,
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int chain_walk = 0;
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raw_spin_lock_irqsave(¤t->pi_lock, flags);
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plist_del(&waiter->list_entry, &lock->wait_list);
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rt_mutex_dequeue(lock, waiter);
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current->pi_blocked_on = NULL;
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raw_spin_unlock_irqrestore(¤t->pi_lock, flags);
|
||||
|
||||
|
|
@ -521,13 +611,13 @@ static void remove_waiter(struct rt_mutex *lock,
|
|||
|
||||
raw_spin_lock_irqsave(&owner->pi_lock, flags);
|
||||
|
||||
plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
|
||||
rt_mutex_dequeue_pi(owner, waiter);
|
||||
|
||||
if (rt_mutex_has_waiters(lock)) {
|
||||
struct rt_mutex_waiter *next;
|
||||
|
||||
next = rt_mutex_top_waiter(lock);
|
||||
plist_add(&next->pi_list_entry, &owner->pi_waiters);
|
||||
rt_mutex_enqueue_pi(owner, next);
|
||||
}
|
||||
__rt_mutex_adjust_prio(owner);
|
||||
|
||||
|
|
@ -537,8 +627,6 @@ static void remove_waiter(struct rt_mutex *lock,
|
|||
raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
|
||||
}
|
||||
|
||||
WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
|
||||
|
||||
if (!chain_walk)
|
||||
return;
|
||||
|
||||
|
|
@ -565,7 +653,7 @@ void rt_mutex_adjust_pi(struct task_struct *task)
|
|||
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
||||
|
||||
waiter = task->pi_blocked_on;
|
||||
if (!waiter || waiter->list_entry.prio == task->prio) {
|
||||
if (!waiter || waiter->task->prio == task->prio) {
|
||||
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
||||
return;
|
||||
}
|
||||
|
|
@ -638,6 +726,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
|
|||
int ret = 0;
|
||||
|
||||
debug_rt_mutex_init_waiter(&waiter);
|
||||
RB_CLEAR_NODE(&waiter.pi_tree_entry);
|
||||
RB_CLEAR_NODE(&waiter.tree_entry);
|
||||
|
||||
raw_spin_lock(&lock->wait_lock);
|
||||
|
||||
|
|
@ -904,7 +994,8 @@ void __rt_mutex_init(struct rt_mutex *lock, const char *name)
|
|||
{
|
||||
lock->owner = NULL;
|
||||
raw_spin_lock_init(&lock->wait_lock);
|
||||
plist_head_init(&lock->wait_list);
|
||||
lock->waiters = RB_ROOT;
|
||||
lock->waiters_leftmost = NULL;
|
||||
|
||||
debug_rt_mutex_init(lock, name);
|
||||
}
|
||||
|
|
|
|||
|
|
@ -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);
|
||||
}
|
||||
|
||||
/*
|
||||
|
|
|
|||
|
|
@ -6635,10 +6635,6 @@ void __init sched_init(void)
|
|||
INIT_HLIST_HEAD(&init_task.preempt_notifiers);
|
||||
#endif
|
||||
|
||||
#ifdef CONFIG_RT_MUTEXES
|
||||
plist_head_init(&init_task.pi_waiters);
|
||||
#endif
|
||||
|
||||
/*
|
||||
* The boot idle thread does lazy MMU switching as well:
|
||||
*/
|
||||
|
|
|
|||
Loading…
Reference in a new issue