X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=kernel%2Frtmutex.c;h=4ab17da46fd80de1690744f9022691923942cb70;hb=d5112a4f31a361409d3c57dc9d58dd69f8014bef;hp=91b699aa658b1ff5368c50e3eaa4248932035a68;hpb=9a11b49a805665e13a56aa067afaf81d43ec1514;p=linux-2.6

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 91b699aa65..4ab17da46f 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -7,6 +7,8 @@
  *  Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
  *  Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt
  *  Copyright (C) 2006 Esben Nielsen
+ *
+ *  See Documentation/rt-mutex-design.txt for details.
  */
 #include <linux/spinlock.h>
 #include <linux/module.h>
@@ -157,7 +159,7 @@ int max_lock_depth = 1024;
  * Decreases task's usage by one - may thus free the task.
  * Returns 0 or -EDEADLK.
  */
-static int rt_mutex_adjust_prio_chain(task_t *task,
+static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 				      int deadlock_detect,
 				      struct rt_mutex *orig_lock,
 				      struct rt_mutex_waiter *orig_waiter,
@@ -249,6 +251,7 @@ static int rt_mutex_adjust_prio_chain(task_t *task,
 
 	/* Grab the next task */
 	task = rt_mutex_owner(lock);
+	get_task_struct(task);
 	spin_lock_irqsave(&task->pi_lock, flags);
 
 	if (waiter == rt_mutex_top_waiter(lock)) {
@@ -267,7 +270,6 @@ static int rt_mutex_adjust_prio_chain(task_t *task,
 		__rt_mutex_adjust_prio(task);
 	}
 
-	get_task_struct(task);
 	spin_unlock_irqrestore(&task->pi_lock, flags);
 
 	top_waiter = rt_mutex_top_waiter(lock);
@@ -282,6 +284,7 @@ static int rt_mutex_adjust_prio_chain(task_t *task,
 	spin_unlock_irqrestore(&task->pi_lock, flags);
  out_put_task:
 	put_task_struct(task);
+
 	return ret;
 }
 
@@ -403,10 +406,10 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 				   struct rt_mutex_waiter *waiter,
 				   int detect_deadlock)
 {
+	struct task_struct *owner = rt_mutex_owner(lock);
 	struct rt_mutex_waiter *top_waiter = waiter;
-	task_t *owner = rt_mutex_owner(lock);
-	int boost = 0, res;
 	unsigned long flags;
+	int chain_walk = 0, res;
 
 	spin_lock_irqsave(&current->pi_lock, flags);
 	__rt_mutex_adjust_prio(current);
@@ -430,25 +433,23 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 		plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
 
 		__rt_mutex_adjust_prio(owner);
-		if (owner->pi_blocked_on) {
-			boost = 1;
-			/* gets dropped in rt_mutex_adjust_prio_chain()! */
-			get_task_struct(owner);
-		}
+		if (owner->pi_blocked_on)
+			chain_walk = 1;
 		spin_unlock_irqrestore(&owner->pi_lock, flags);
 	}
-	else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
-		spin_lock_irqsave(&owner->pi_lock, flags);
-		if (owner->pi_blocked_on) {
-			boost = 1;
-			/* gets dropped in rt_mutex_adjust_prio_chain()! */
-			get_task_struct(owner);
-		}
-		spin_unlock_irqrestore(&owner->pi_lock, flags);
-	}
-	if (!boost)
+	else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock))
+		chain_walk = 1;
+
+	if (!chain_walk)
 		return 0;
 
+	/*
+	 * The owner can't disappear while holding a lock,
+	 * so the owner struct is protected by wait_lock.
+	 * Gets dropped in rt_mutex_adjust_prio_chain()!
+	 */
+	get_task_struct(owner);
+
 	spin_unlock(&lock->wait_lock);
 
 	res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
@@ -527,9 +528,9 @@ static void remove_waiter(struct rt_mutex *lock,
 			  struct rt_mutex_waiter *waiter)
 {
 	int first = (waiter == rt_mutex_top_waiter(lock));
-	int boost = 0;
-	task_t *owner = rt_mutex_owner(lock);
+	struct task_struct *owner = rt_mutex_owner(lock);
 	unsigned long flags;
+	int chain_walk = 0;
 
 	spin_lock_irqsave(&current->pi_lock, flags);
 	plist_del(&waiter->list_entry, &lock->wait_list);
@@ -551,19 +552,20 @@ static void remove_waiter(struct rt_mutex *lock,
 		}
 		__rt_mutex_adjust_prio(owner);
 
-		if (owner->pi_blocked_on) {
-			boost = 1;
-			/* gets dropped in rt_mutex_adjust_prio_chain()! */
-			get_task_struct(owner);
-		}
+		if (owner->pi_blocked_on)
+			chain_walk = 1;
+
 		spin_unlock_irqrestore(&owner->pi_lock, flags);
 	}
 
 	WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
 
-	if (!boost)
+	if (!chain_walk)
 		return;
 
+	/* gets dropped in rt_mutex_adjust_prio_chain()! */
+	get_task_struct(owner);
+
 	spin_unlock(&lock->wait_lock);
 
 	rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);
@@ -589,10 +591,10 @@ void rt_mutex_adjust_pi(struct task_struct *task)
 		return;
 	}
 
-	/* gets dropped in rt_mutex_adjust_prio_chain()! */
-	get_task_struct(task);
 	spin_unlock_irqrestore(&task->pi_lock, flags);
 
+	/* gets dropped in rt_mutex_adjust_prio_chain()! */
+	get_task_struct(task);
 	rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
 }