Messages in this thread Patch in this message | | | Subject | [RFC][PATCH 19/22] rtmutex: turn the plist into an rb-tree | From | Raistlin <> | Date | Fri, 29 Oct 2010 08:42:01 +0200 |
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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 increses.
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 chenged 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> --- include/linux/init_task.h | 10 +++ include/linux/rtmutex.h | 13 +--- include/linux/sched.h | 4 +- kernel/fork.c | 3 +- kernel/rtmutex-debug.c | 8 +-- kernel/rtmutex.c | 135 +++++++++++++++++++++++++++++++++++---------- kernel/rtmutex_common.h | 22 ++++---- kernel/sched.c | 4 - 8 files changed, 137 insertions(+), 62 deletions(-)
diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 1f8c06c..f4f7567 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -10,6 +10,7 @@ #include <linux/pid_namespace.h> #include <linux/user_namespace.h> #include <linux/securebits.h> +#include <linux/rbtree.h> #include <net/net_namespace.h> extern struct files_struct init_files; @@ -110,6 +111,14 @@ extern struct cred init_cred; # define INIT_PERF_EVENTS(tsk) #endif +#ifdef CONFIG_RT_MUTEXES +# define INIT_RT_MUTEXES \ + .pi_waiters = RB_ROOT, \ + .pi_waiters_leftmost = NULL, +#else +# define INIT_RT_MUTEXES +#endif + /* * INIT_TASK is used to set up the first task table, touch at * your own risk!. Base=0, limit=0x1fffff (=2MB) @@ -178,6 +187,7 @@ extern struct cred init_cred; INIT_FTRACE_GRAPH \ INIT_TRACE_RECURSION \ INIT_TASK_RCU_PREEMPT(tsk) \ + INIT_RT_MUTEXES \ } diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h index 8d522ff..bd7cd02 100644 --- a/include/linux/rtmutex.h +++ b/include/linux/rtmutex.h @@ -13,7 +13,7 @@ #define __LINUX_RT_MUTEX_H #include <linux/linkage.h> -#include <linux/plist.h> +#include <linux/rbtree.h> #include <linux/spinlock_types.h> extern int max_lock_depth; /* for sysctl */ @@ -27,7 +27,8 @@ extern int max_lock_depth; /* for sysctl */ */ struct rt_mutex { raw_spinlock_t wait_lock; - struct plist_head wait_list; + struct rb_root waiters; + struct rb_node *waiters_leftmost; struct task_struct *owner; #ifdef CONFIG_DEBUG_RT_MUTEXES int save_state; @@ -98,12 +99,4 @@ extern int rt_mutex_trylock(struct rt_mutex *lock); extern void rt_mutex_unlock(struct rt_mutex *lock); -#ifdef CONFIG_RT_MUTEXES -# define INIT_RT_MUTEXES(tsk) \ - .pi_waiters = PLIST_HEAD_INIT(tsk.pi_waiters, tsk.pi_lock), \ - INIT_RT_MUTEX_DEBUG(tsk) -#else -# define INIT_RT_MUTEXES(tsk) -#endif - #endif diff --git a/include/linux/sched.h b/include/linux/sched.h index 8806c1f..c3d1f17b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -56,6 +56,7 @@ struct sched_param { #include <linux/types.h> #include <linux/timex.h> #include <linux/jiffies.h> +#include <linux/plist.h> #include <linux/rbtree.h> #include <linux/thread_info.h> #include <linux/cpumask.h> @@ -1530,7 +1531,8 @@ struct task_struct { #ifdef CONFIG_RT_MUTEXES /* PI waiters blocked on a rt_mutex held by this task */ - struct plist_head pi_waiters; + struct rb_root pi_waiters; + struct rb_node *pi_waiters_leftmost; /* Deadlock detection and priority inheritance handling */ struct rt_mutex_waiter *pi_blocked_on; #endif diff --git a/kernel/fork.c b/kernel/fork.c index 3b159c5..aceb248 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -935,7 +935,8 @@ static void rt_mutex_init_task(struct task_struct *p) { raw_spin_lock_init(&p->pi_lock); #ifdef CONFIG_RT_MUTEXES - plist_head_init_raw(&p->pi_waiters, &p->pi_lock); + p->pi_waiters = RB_ROOT; + p->pi_waiters_leftmost = NULL; p->pi_blocked_on = NULL; #endif } diff --git a/kernel/rtmutex-debug.c b/kernel/rtmutex-debug.c index ddabb54..7cc8376 100644 --- a/kernel/rtmutex-debug.c +++ b/kernel/rtmutex-debug.c @@ -23,7 +23,7 @@ #include <linux/kallsyms.h> #include <linux/syscalls.h> #include <linux/interrupt.h> -#include <linux/plist.h> +#include <linux/rbtree.h> #include <linux/fs.h> #include <linux/debug_locks.h> @@ -111,7 +111,7 @@ static void printk_lock(struct rt_mutex *lock, int print_owner) void rt_mutex_debug_task_free(struct task_struct *task) { - WARN_ON(!plist_head_empty(&task->pi_waiters)); + WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters)); WARN_ON(task->pi_blocked_on); } @@ -205,16 +205,12 @@ void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock) void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) { memset(waiter, 0x11, sizeof(*waiter)); - plist_node_init(&waiter->list_entry, MAX_PRIO); - plist_node_init(&waiter->pi_list_entry, MAX_PRIO); waiter->deadlock_task_pid = NULL; } void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter) { put_pid(waiter->deadlock_task_pid); - TRACE_WARN_ON(!plist_node_empty(&waiter->list_entry)); - TRACE_WARN_ON(!plist_node_empty(&waiter->pi_list_entry)); TRACE_WARN_ON(waiter->task); memset(waiter, 0x22, sizeof(*waiter)); } diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index a960481..2e9c0dc 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -97,6 +97,90 @@ static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) } #endif +static inline int +rt_mutex_waiter_less(struct rt_mutex_waiter *left, + struct rt_mutex_waiter *right) +{ + if (left->task->prio < right->task->prio) + return 1; + + /* + * If both tasks are dl_task(), we check their deadlines. + */ + if (dl_prio(left->task->prio) && dl_prio(right->task->prio)) + return left->task->dl.deadline < right->task->dl.deadline; +} + +static void +rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) +{ + struct rb_node **link = &lock->waiters.rb_node; + struct rb_node *parent = NULL; + struct rt_mutex_waiter *entry; + int leftmost = 1; + + while (*link) { + parent = *link; + entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry); + if (rt_mutex_waiter_less(waiter, entry)) { + link = &parent->rb_left; + } else { + link = &parent->rb_right; + leftmost = 0; + } + } + + if (leftmost) + lock->waiters_leftmost = &waiter->tree_entry; + + rb_link_node(&waiter->tree_entry, parent, link); + rb_insert_color(&waiter->tree_entry, &lock->waiters); +} + +static void +rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) +{ + if (lock->waiters_leftmost == &waiter->tree_entry) + lock->waiters_leftmost = rb_next(&waiter->tree_entry); + + rb_erase(&waiter->tree_entry, &lock->waiters); +} + +static void +rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) +{ + struct rb_node **link = &task->pi_waiters.rb_node; + struct rb_node *parent = NULL; + struct rt_mutex_waiter *entry; + int leftmost = 1; + + while (*link) { + parent = *link; + entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry); + if (rt_mutex_waiter_less(waiter, entry)) { + link = &parent->rb_left; + } else { + link = &parent->rb_right; + leftmost = 0; + } + } + + if (leftmost) + task->pi_waiters_leftmost = &waiter->pi_tree_entry; + + rb_link_node(&waiter->pi_tree_entry, parent, link); + rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters); +} + +static void +rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) +{ + if (task->pi_waiters_leftmost == &waiter->pi_tree_entry) + task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry); + + rb_erase(&waiter->pi_tree_entry, &task->pi_waiters); +} + /* * Calculate task priority from the waiter list priority * @@ -108,7 +192,7 @@ int rt_mutex_getprio(struct task_struct *task) if (likely(!task_has_pi_waiters(task))) return task->normal_prio; - return min(task_top_pi_waiter(task)->pi_list_entry.prio, + return min(task_top_pi_waiter(task)->task->prio, task->normal_prio); } @@ -227,7 +311,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, * When deadlock detection is off then we check, if further * priority adjustment is necessary. */ - if (!detect_deadlock && waiter->list_entry.prio == task->prio) + if (!detect_deadlock && waiter->task->prio == task->prio) goto out_unlock_pi; lock = waiter->lock; @@ -248,9 +332,8 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, top_waiter = rt_mutex_top_waiter(lock); /* Requeue the waiter */ - plist_del(&waiter->list_entry, &lock->wait_list); - waiter->list_entry.prio = task->prio; - plist_add(&waiter->list_entry, &lock->wait_list); + rt_mutex_dequeue(lock, waiter); + rt_mutex_enqueue(lock, waiter); /* Release the task */ raw_spin_unlock_irqrestore(&task->pi_lock, flags); @@ -263,17 +346,15 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, if (waiter == rt_mutex_top_waiter(lock)) { /* Boost the owner */ - plist_del(&top_waiter->pi_list_entry, &task->pi_waiters); - waiter->pi_list_entry.prio = waiter->list_entry.prio; - plist_add(&waiter->pi_list_entry, &task->pi_waiters); + rt_mutex_dequeue_pi(task, top_waiter); + rt_mutex_enqueue_pi(task, waiter); __rt_mutex_adjust_prio(task); } else if (top_waiter == waiter) { /* Deboost the owner */ - plist_del(&waiter->pi_list_entry, &task->pi_waiters); + rt_mutex_dequeue_pi(task, waiter); waiter = rt_mutex_top_waiter(lock); - waiter->pi_list_entry.prio = waiter->list_entry.prio; - plist_add(&waiter->pi_list_entry, &task->pi_waiters); + rt_mutex_enqueue_pi(task, waiter); __rt_mutex_adjust_prio(task); } @@ -331,7 +412,7 @@ static inline int try_to_steal_lock(struct rt_mutex *lock, /* No chain handling, pending owner is not blocked on anything: */ next = rt_mutex_top_waiter(lock); - plist_del(&next->pi_list_entry, &pendowner->pi_waiters); + rt_mutex_dequeue_pi(pendowner, next); __rt_mutex_adjust_prio(pendowner); raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); @@ -351,7 +432,7 @@ static inline int try_to_steal_lock(struct rt_mutex *lock, */ if (likely(next->task != task)) { raw_spin_lock_irqsave(&task->pi_lock, flags); - plist_add(&next->pi_list_entry, &task->pi_waiters); + rt_mutex_enqueue_pi(task, next); __rt_mutex_adjust_prio(task); raw_spin_unlock_irqrestore(&task->pi_lock, flags); } @@ -424,13 +505,11 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, __rt_mutex_adjust_prio(task); waiter->task = task; waiter->lock = lock; - plist_node_init(&waiter->list_entry, task->prio); - plist_node_init(&waiter->pi_list_entry, task->prio); /* Get the top priority waiter on the lock */ if (rt_mutex_has_waiters(lock)) top_waiter = rt_mutex_top_waiter(lock); - plist_add(&waiter->list_entry, &lock->wait_list); + rt_mutex_enqueue(lock, waiter); task->pi_blocked_on = waiter; @@ -438,9 +517,8 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, if (waiter == rt_mutex_top_waiter(lock)) { raw_spin_lock_irqsave(&owner->pi_lock, flags); - plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters); - plist_add(&waiter->pi_list_entry, &owner->pi_waiters); - + rt_mutex_dequeue_pi(owner, top_waiter); + rt_mutex_enqueue_pi(owner, waiter); __rt_mutex_adjust_prio(owner); if (owner->pi_blocked_on) chain_walk = 1; @@ -486,7 +564,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock) raw_spin_lock_irqsave(¤t->pi_lock, flags); waiter = rt_mutex_top_waiter(lock); - plist_del(&waiter->list_entry, &lock->wait_list); + rt_mutex_dequeue(lock, waiter); /* * Remove it from current->pi_waiters. We do not adjust a @@ -494,7 +572,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock) * boosted mode and go back to normal after releasing * lock->wait_lock. */ - plist_del(&waiter->pi_list_entry, ¤t->pi_waiters); + rt_mutex_dequeue_pi(current, waiter); pendowner = waiter->task; waiter->task = NULL; @@ -521,7 +599,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock) struct rt_mutex_waiter *next; next = rt_mutex_top_waiter(lock); - plist_add(&next->pi_list_entry, &pendowner->pi_waiters); + rt_mutex_enqueue_pi(pendowner, next); } raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); @@ -542,7 +620,7 @@ static void remove_waiter(struct rt_mutex *lock, int chain_walk = 0; raw_spin_lock_irqsave(¤t->pi_lock, flags); - plist_del(&waiter->list_entry, &lock->wait_list); + rt_mutex_dequeue(lock, waiter); waiter->task = NULL; current->pi_blocked_on = NULL; raw_spin_unlock_irqrestore(¤t->pi_lock, flags); @@ -551,13 +629,13 @@ 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); @@ -567,8 +645,6 @@ 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; @@ -595,7 +671,7 @@ 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; } @@ -971,7 +1047,8 @@ void __rt_mutex_init(struct rt_mutex *lock, const char *name) { lock->owner = NULL; raw_spin_lock_init(&lock->wait_lock); - plist_head_init_raw(&lock->wait_list, &lock->wait_lock); + lock->waiters = RB_ROOT; + lock->waiters_leftmost = NULL; debug_rt_mutex_init(lock, name); } diff --git a/kernel/rtmutex_common.h b/kernel/rtmutex_common.h index 97a2f81..84b9eea 100644 --- a/kernel/rtmutex_common.h +++ b/kernel/rtmutex_common.h @@ -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); } /* diff --git a/kernel/sched.c b/kernel/sched.c index 4d291e3..853473a 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -8504,10 +8504,6 @@ void __init sched_init(void) open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); #endif -#ifdef CONFIG_RT_MUTEXES - plist_head_init_raw(&init_task.pi_waiters, &init_task.pi_lock); -#endif - /* * The boot idle thread does lazy MMU switching as well: */ -- 1.7.2.3
-- <<This happens because I choose it to happen!>> (Raistlin Majere) ---------------------------------------------------------------------- Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy) http://blog.linux.it/raistlin / raistlin@ekiga.net / dario.faggioli@jabber.org [unhandled content-type:application/pgp-signature]
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