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authorThomas Gleixner <tglx@linutronix.de>2006-06-27 05:55:02 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-27 20:32:48 -0400
commit95e02ca9bb5324360e7dea1ea1c563036d84a5e6 (patch)
tree0336dd808abe113b42f53a8f700d50ea6ba674ff /kernel
parent0bafd214e4ba55dc1fb81a3031d0249292f1bc05 (diff)
[PATCH] rtmutex: Propagate priority settings into PI lock chains
When the priority of a task, which is blocked on a lock, changes we must propagate this change into the PI lock chain. Therefor the chain walk code is changed to get rid of the references to current to avoid false positives in the deadlock detector, as setscheduler might be called by a task which holds the lock on which the task whose priority is changed is blocked. Also add some comments about the get/put_task_struct usage to avoid confusion. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rtmutex.c42
-rw-r--r--kernel/sched.c2
2 files changed, 38 insertions, 6 deletions
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 3fc0f0680ca2..45d61016da57 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -160,7 +160,8 @@ int max_lock_depth = 1024;
160static int rt_mutex_adjust_prio_chain(task_t *task, 160static int rt_mutex_adjust_prio_chain(task_t *task,
161 int deadlock_detect, 161 int deadlock_detect,
162 struct rt_mutex *orig_lock, 162 struct rt_mutex *orig_lock,
163 struct rt_mutex_waiter *orig_waiter 163 struct rt_mutex_waiter *orig_waiter,
164 struct task_struct *top_task
164 __IP_DECL__) 165 __IP_DECL__)
165{ 166{
166 struct rt_mutex *lock; 167 struct rt_mutex *lock;
@@ -189,7 +190,7 @@ static int rt_mutex_adjust_prio_chain(task_t *task,
189 prev_max = max_lock_depth; 190 prev_max = max_lock_depth;
190 printk(KERN_WARNING "Maximum lock depth %d reached " 191 printk(KERN_WARNING "Maximum lock depth %d reached "
191 "task: %s (%d)\n", max_lock_depth, 192 "task: %s (%d)\n", max_lock_depth,
192 current->comm, current->pid); 193 top_task->comm, top_task->pid);
193 } 194 }
194 put_task_struct(task); 195 put_task_struct(task);
195 196
@@ -229,7 +230,7 @@ static int rt_mutex_adjust_prio_chain(task_t *task,
229 } 230 }
230 231
231 /* Deadlock detection */ 232 /* Deadlock detection */
232 if (lock == orig_lock || rt_mutex_owner(lock) == current) { 233 if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
233 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); 234 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
234 spin_unlock(&lock->wait_lock); 235 spin_unlock(&lock->wait_lock);
235 ret = deadlock_detect ? -EDEADLK : 0; 236 ret = deadlock_detect ? -EDEADLK : 0;
@@ -433,6 +434,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
433 __rt_mutex_adjust_prio(owner); 434 __rt_mutex_adjust_prio(owner);
434 if (owner->pi_blocked_on) { 435 if (owner->pi_blocked_on) {
435 boost = 1; 436 boost = 1;
437 /* gets dropped in rt_mutex_adjust_prio_chain()! */
436 get_task_struct(owner); 438 get_task_struct(owner);
437 } 439 }
438 spin_unlock_irqrestore(&owner->pi_lock, flags); 440 spin_unlock_irqrestore(&owner->pi_lock, flags);
@@ -441,6 +443,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
441 spin_lock_irqsave(&owner->pi_lock, flags); 443 spin_lock_irqsave(&owner->pi_lock, flags);
442 if (owner->pi_blocked_on) { 444 if (owner->pi_blocked_on) {
443 boost = 1; 445 boost = 1;
446 /* gets dropped in rt_mutex_adjust_prio_chain()! */
444 get_task_struct(owner); 447 get_task_struct(owner);
445 } 448 }
446 spin_unlock_irqrestore(&owner->pi_lock, flags); 449 spin_unlock_irqrestore(&owner->pi_lock, flags);
@@ -450,8 +453,8 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
450 453
451 spin_unlock(&lock->wait_lock); 454 spin_unlock(&lock->wait_lock);
452 455
453 res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, 456 res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
454 waiter __IP__); 457 current __IP__);
455 458
456 spin_lock(&lock->wait_lock); 459 spin_lock(&lock->wait_lock);
457 460
@@ -552,6 +555,7 @@ static void remove_waiter(struct rt_mutex *lock,
552 555
553 if (owner->pi_blocked_on) { 556 if (owner->pi_blocked_on) {
554 boost = 1; 557 boost = 1;
558 /* gets dropped in rt_mutex_adjust_prio_chain()! */
555 get_task_struct(owner); 559 get_task_struct(owner);
556 } 560 }
557 spin_unlock_irqrestore(&owner->pi_lock, flags); 561 spin_unlock_irqrestore(&owner->pi_lock, flags);
@@ -564,12 +568,37 @@ static void remove_waiter(struct rt_mutex *lock,
564 568
565 spin_unlock(&lock->wait_lock); 569 spin_unlock(&lock->wait_lock);
566 570
567 rt_mutex_adjust_prio_chain(owner, 0, lock, NULL __IP__); 571 rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current __IP__);
568 572
569 spin_lock(&lock->wait_lock); 573 spin_lock(&lock->wait_lock);
570} 574}
571 575
572/* 576/*
577 * Recheck the pi chain, in case we got a priority setting
578 *
579 * Called from sched_setscheduler
580 */
581void rt_mutex_adjust_pi(struct task_struct *task)
582{
583 struct rt_mutex_waiter *waiter;
584 unsigned long flags;
585
586 spin_lock_irqsave(&task->pi_lock, flags);
587
588 waiter = task->pi_blocked_on;
589 if (!waiter || waiter->list_entry.prio == task->prio) {
590 spin_unlock_irqrestore(&task->pi_lock, flags);
591 return;
592 }
593
594 /* gets dropped in rt_mutex_adjust_prio_chain()! */
595 get_task_struct(task);
596 spin_unlock_irqrestore(&task->pi_lock, flags);
597
598 rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task __RET_IP__);
599}
600
601/*
573 * Slow path lock function: 602 * Slow path lock function:
574 */ 603 */
575static int __sched 604static int __sched
@@ -636,6 +665,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
636 if (unlikely(ret)) 665 if (unlikely(ret))
637 break; 666 break;
638 } 667 }
668
639 spin_unlock(&lock->wait_lock); 669 spin_unlock(&lock->wait_lock);
640 670
641 debug_rt_mutex_print_deadlock(&waiter); 671 debug_rt_mutex_print_deadlock(&waiter);
diff --git a/kernel/sched.c b/kernel/sched.c
index 7a30addfd235..2629c1711fd6 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4070,6 +4070,8 @@ recheck:
4070 __task_rq_unlock(rq); 4070 __task_rq_unlock(rq);
4071 spin_unlock_irqrestore(&p->pi_lock, flags); 4071 spin_unlock_irqrestore(&p->pi_lock, flags);
4072 4072
4073 rt_mutex_adjust_pi(p);
4074
4073 return 0; 4075 return 0;
4074} 4076}
4075EXPORT_SYMBOL_GPL(sched_setscheduler); 4077EXPORT_SYMBOL_GPL(sched_setscheduler);