From ccaa8d657117bb1876d471bd91579d774106778d Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 25 Jan 2011 23:17:32 +0100 Subject: rtmutex-tester: Remove BKL tests The BKL is going away, no need to test it any more. I left the definitions of the test case numbers in, so that the other tests do not get renumbered. Signed-off-by: Arnd Bergmann Cc: Arjan van de Ven Cc: Ingo Molnar Cc: Andrew Morton LKML-Reference: <1295993854-4971-19-git-send-email-arnd@arndb.de> Signed-off-by: Thomas Gleixner --- kernel/rtmutex-tester.c | 39 ++++----------------------------------- 1 file changed, 4 insertions(+), 35 deletions(-) (limited to 'kernel') diff --git a/kernel/rtmutex-tester.c b/kernel/rtmutex-tester.c index 66cb89bc5ef1..d5b543506cbc 100644 --- a/kernel/rtmutex-tester.c +++ b/kernel/rtmutex-tester.c @@ -9,7 +9,6 @@ #include #include #include -#include #include #include #include @@ -27,7 +26,6 @@ struct test_thread_data { int opcode; int opdata; int mutexes[MAX_RT_TEST_MUTEXES]; - int bkl; int event; struct sys_device sysdev; }; @@ -46,8 +44,8 @@ enum test_opcodes { RTTEST_LOCKINTNOWAIT, /* 6 Lock interruptible no wait in wakeup, data = lockindex */ RTTEST_LOCKCONT, /* 7 Continue locking after the wakeup delay */ RTTEST_UNLOCK, /* 8 Unlock, data = lockindex */ - RTTEST_LOCKBKL, /* 9 Lock BKL */ - RTTEST_UNLOCKBKL, /* 10 Unlock BKL */ + RTTEST_LOCKBKL, /* 9 Was: Lock BKL */ + RTTEST_UNLOCKBKL, /* 10 Was: Unlock BKL */ RTTEST_SIGNAL, /* 11 Signal other test thread, data = thread id */ RTTEST_RESETEVENT = 98, /* 98 Reset event counter */ RTTEST_RESET = 99, /* 99 Reset all pending operations */ @@ -74,13 +72,6 @@ static int handle_op(struct test_thread_data *td, int lockwakeup) td->mutexes[i] = 0; } } - - if (!lockwakeup && td->bkl == 4) { -#ifdef CONFIG_LOCK_KERNEL - unlock_kernel(); -#endif - td->bkl = 0; - } return 0; case RTTEST_RESETEVENT: @@ -131,25 +122,6 @@ static int handle_op(struct test_thread_data *td, int lockwakeup) td->mutexes[id] = 0; return 0; - case RTTEST_LOCKBKL: - if (td->bkl) - return 0; - td->bkl = 1; -#ifdef CONFIG_LOCK_KERNEL - lock_kernel(); -#endif - td->bkl = 4; - return 0; - - case RTTEST_UNLOCKBKL: - if (td->bkl != 4) - break; -#ifdef CONFIG_LOCK_KERNEL - unlock_kernel(); -#endif - td->bkl = 0; - return 0; - default: break; } @@ -196,7 +168,6 @@ void schedule_rt_mutex_test(struct rt_mutex *mutex) td->event = atomic_add_return(1, &rttest_event); break; - case RTTEST_LOCKBKL: default: break; } @@ -229,8 +200,6 @@ void schedule_rt_mutex_test(struct rt_mutex *mutex) td->event = atomic_add_return(1, &rttest_event); return; - case RTTEST_LOCKBKL: - return; default: return; } @@ -380,11 +349,11 @@ static ssize_t sysfs_test_status(struct sys_device *dev, struct sysdev_attribute spin_lock(&rttest_lock); curr += sprintf(curr, - "O: %4d, E:%8d, S: 0x%08lx, P: %4d, N: %4d, B: %p, K: %d, M:", + "O: %4d, E:%8d, S: 0x%08lx, P: %4d, N: %4d, B: %p, M:", td->opcode, td->event, tsk->state, (MAX_RT_PRIO - 1) - tsk->prio, (MAX_RT_PRIO - 1) - tsk->normal_prio, - tsk->pi_blocked_on, td->bkl); + tsk->pi_blocked_on); for (i = MAX_RT_TEST_MUTEXES - 1; i >=0 ; i--) curr += sprintf(curr, "%d", td->mutexes[i]); -- cgit v1.2.3 From 10389a15e25fd4784d42de7e0e3fc8c242f2011d Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 23 Jan 2011 15:25:56 +0100 Subject: cred: Replace deprecated spinlock initialization SPIN_LOCK_UNLOCK is deprecated. Use the lockdep capable variant instead. Signed-off-by: Thomas Gleixner --- kernel/cred.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/cred.c b/kernel/cred.c index 6a1aa004e376..b5496e81b0f7 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -35,7 +35,7 @@ static struct kmem_cache *cred_jar; static struct thread_group_cred init_tgcred = { .usage = ATOMIC_INIT(2), .tgid = 0, - .lock = SPIN_LOCK_UNLOCKED, + .lock = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock), }; #endif -- cgit v1.2.3 From 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Fri, 14 Jan 2011 17:09:41 +0800 Subject: rtmutex: Simplify PI algorithm and make highest prio task get lock In current rtmutex, the pending owner may be boosted by the tasks in the rtmutex's waitlist when the pending owner is deboosted or a task in the waitlist is boosted. This boosting is unrelated, because the pending owner does not really take the rtmutex. It is not reasonable. Example. time1: A(high prio) onwers the rtmutex. B(mid prio) and C (low prio) in the waitlist. time2 A release the lock, B becomes the pending owner A(or other high prio task) continues to run. B's prio is lower than A, so B is just queued at the runqueue. time3 A or other high prio task sleeps, but we have passed some time The B and C's prio are changed in the period (time2 ~ time3) due to boosting or deboosting. Now C has the priority higher than B. ***Is it reasonable that C has to boost B and help B to get the rtmutex? NO!! I think, it is unrelated/unneed boosting before B really owns the rtmutex. We should give C a chance to beat B and win the rtmutex. This is the motivation of this patch. This patch *ensures* only the top waiter or higher priority task can take the lock. How? 1) we don't dequeue the top waiter when unlock, if the top waiter is changed, the old top waiter will fail and go to sleep again. 2) when requiring lock, it will get the lock when the lock is not taken and: there is no waiter OR higher priority than waiters OR it is top waiter. 3) In any time, the top waiter is changed, the top waiter will be woken up. The algorithm is much simpler than before, no pending owner, no boosting for pending owner. Other advantage of this patch: 1) The states of a rtmutex are reduced a half, easier to read the code. 2) the codes become shorter. 3) top waiter is not dequeued until it really take the lock: they will retain FIFO when it is stolen. Not advantage nor disadvantage 1) Even we may wakeup multiple waiters(any time when top waiter changed), we hardly cause "thundering herd", the number of wokenup task is likely 1 or very little. 2) two APIs are changed. rt_mutex_owner() will not return pending owner, it will return NULL when the top waiter is going to take the lock. rt_mutex_next_owner() always return the top waiter. will not return NULL if we have waiters because the top waiter is not dequeued. I have fixed the code that use these APIs. need updated after this patch is accepted 1) Document/* 2) the testcase scripts/rt-tester/t4-l2-pi-deboost.tst Signed-off-by: Lai Jiangshan LKML-Reference: <4D3012D5.4060709@cn.fujitsu.com> Reviewed-by: Steven Rostedt Signed-off-by: Steven Rostedt --- kernel/futex.c | 22 ++-- kernel/rtmutex-debug.c | 1 - kernel/rtmutex.c | 318 +++++++++++++++++------------------------------- kernel/rtmutex_common.h | 16 +-- 4 files changed, 127 insertions(+), 230 deletions(-) (limited to 'kernel') diff --git a/kernel/futex.c b/kernel/futex.c index b766d28accd6..64c38115c7b6 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1556,10 +1556,10 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, /* * We are here either because we stole the rtmutex from the - * pending owner or we are the pending owner which failed to - * get the rtmutex. We have to replace the pending owner TID - * in the user space variable. This must be atomic as we have - * to preserve the owner died bit here. + * previous highest priority waiter or we are the highest priority + * waiter but failed to get the rtmutex the first time. + * We have to replace the newowner TID in the user space variable. + * This must be atomic as we have to preserve the owner died bit here. * * Note: We write the user space value _before_ changing the pi_state * because we can fault here. Imagine swapped out pages or a fork @@ -1608,8 +1608,8 @@ retry: /* * To handle the page fault we need to drop the hash bucket - * lock here. That gives the other task (either the pending - * owner itself or the task which stole the rtmutex) the + * lock here. That gives the other task (either the highest priority + * waiter itself or the task which stole the rtmutex) the * chance to try the fixup of the pi_state. So once we are * back from handling the fault we need to check the pi_state * after reacquiring the hash bucket lock and before trying to @@ -1685,18 +1685,20 @@ static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) /* * pi_state is incorrect, some other task did a lock steal and * we returned due to timeout or signal without taking the - * rt_mutex. Too late. We can access the rt_mutex_owner without - * locking, as the other task is now blocked on the hash bucket - * lock. Fix the state up. + * rt_mutex. Too late. */ + raw_spin_lock(&q->pi_state->pi_mutex.wait_lock); owner = rt_mutex_owner(&q->pi_state->pi_mutex); + if (!owner) + owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); + raw_spin_unlock(&q->pi_state->pi_mutex.wait_lock); ret = fixup_pi_state_owner(uaddr, q, owner); goto out; } /* * Paranoia check. If we did not take the lock, then we should not be - * the owner, nor the pending owner, of the rt_mutex. + * the owner of the rt_mutex. */ if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " diff --git a/kernel/rtmutex-debug.c b/kernel/rtmutex-debug.c index ddabb54bb5c8..3c7cbc2c33be 100644 --- a/kernel/rtmutex-debug.c +++ b/kernel/rtmutex-debug.c @@ -215,7 +215,6 @@ 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 a9604815786a..ab449117aaf2 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -20,41 +20,34 @@ /* * lock->owner state tracking: * - * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1 - * are used to keep track of the "owner is pending" and "lock has - * waiters" state. + * lock->owner holds the task_struct pointer of the owner. Bit 0 + * is used to keep track of the "lock has waiters" state. * - * owner bit1 bit0 - * NULL 0 0 lock is free (fast acquire possible) - * NULL 0 1 invalid state - * NULL 1 0 Transitional State* - * NULL 1 1 invalid state - * taskpointer 0 0 lock is held (fast release possible) - * taskpointer 0 1 task is pending owner - * taskpointer 1 0 lock is held and has waiters - * taskpointer 1 1 task is pending owner and lock has more waiters - * - * Pending ownership is assigned to the top (highest priority) - * waiter of the lock, when the lock is released. The thread is woken - * up and can now take the lock. Until the lock is taken (bit 0 - * cleared) a competing higher priority thread can steal the lock - * which puts the woken up thread back on the waiters list. + * owner bit0 + * NULL 0 lock is free (fast acquire possible) + * NULL 1 lock is free and has waiters and the top waiter + * is going to take the lock* + * taskpointer 0 lock is held (fast release possible) + * taskpointer 1 lock is held and has waiters** * * The fast atomic compare exchange based acquire and release is only - * possible when bit 0 and 1 of lock->owner are 0. + * possible when bit 0 of lock->owner is 0. + * + * (*) It also can be a transitional state when grabbing the lock + * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock, + * we need to set the bit0 before looking at the lock, and the owner may be + * NULL in this small time, hence this can be a transitional state. * - * (*) There's a small time where the owner can be NULL and the - * "lock has waiters" bit is set. This can happen when grabbing the lock. - * To prevent a cmpxchg of the owner releasing the lock, we need to set this - * bit before looking at the lock, hence the reason this is a transitional - * state. + * (**) There is a small time when bit 0 is set but there are no + * waiters. This can happen when grabbing the lock in the slow path. + * To prevent a cmpxchg of the owner releasing the lock, we need to + * set this bit before looking at the lock. */ static void -rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner, - unsigned long mask) +rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) { - unsigned long val = (unsigned long)owner | mask; + unsigned long val = (unsigned long)owner; if (rt_mutex_has_waiters(lock)) val |= RT_MUTEX_HAS_WAITERS; @@ -203,15 +196,14 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, * reached or the state of the chain has changed while we * dropped the locks. */ - if (!waiter || !waiter->task) + if (!waiter) goto out_unlock_pi; /* * Check the orig_waiter state. After we dropped the locks, - * the previous owner of the lock might have released the lock - * and made us the pending owner: + * the previous owner of the lock might have released the lock. */ - if (orig_waiter && !orig_waiter->task) + if (orig_waiter && !rt_mutex_owner(orig_lock)) goto out_unlock_pi; /* @@ -254,6 +246,17 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, /* Release the task */ raw_spin_unlock_irqrestore(&task->pi_lock, flags); + if (!rt_mutex_owner(lock)) { + /* + * If the requeue above changed the top waiter, then we need + * to wake the new top waiter up to try to get the lock. + */ + + if (top_waiter != rt_mutex_top_waiter(lock)) + wake_up_process(rt_mutex_top_waiter(lock)->task); + raw_spin_unlock(&lock->wait_lock); + goto out_put_task; + } put_task_struct(task); /* Grab the next task */ @@ -295,79 +298,17 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, return ret; } -/* - * Optimization: check if we can steal the lock from the - * assigned pending owner [which might not have taken the - * lock yet]: - */ -static inline int try_to_steal_lock(struct rt_mutex *lock, - struct task_struct *task) -{ - struct task_struct *pendowner = rt_mutex_owner(lock); - struct rt_mutex_waiter *next; - unsigned long flags; - - if (!rt_mutex_owner_pending(lock)) - return 0; - - if (pendowner == task) - return 1; - - raw_spin_lock_irqsave(&pendowner->pi_lock, flags); - if (task->prio >= pendowner->prio) { - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - return 0; - } - - /* - * Check if a waiter is enqueued on the pending owners - * pi_waiters list. Remove it and readjust pending owners - * priority. - */ - if (likely(!rt_mutex_has_waiters(lock))) { - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - return 1; - } - - /* 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_adjust_prio(pendowner); - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - - /* - * We are going to steal the lock and a waiter was - * enqueued on the pending owners pi_waiters queue. So - * we have to enqueue this waiter into - * task->pi_waiters list. This covers the case, - * where task is boosted because it holds another - * lock and gets unboosted because the booster is - * interrupted, so we would delay a waiter with higher - * priority as task->normal_prio. - * - * Note: in the rare case of a SCHED_OTHER task changing - * its priority and thus stealing the lock, next->task - * might be task: - */ - if (likely(next->task != task)) { - raw_spin_lock_irqsave(&task->pi_lock, flags); - plist_add(&next->pi_list_entry, &task->pi_waiters); - __rt_mutex_adjust_prio(task); - raw_spin_unlock_irqrestore(&task->pi_lock, flags); - } - return 1; -} - /* * Try to take an rt-mutex * - * This fails - * - when the lock has a real owner - * - when a different pending owner exists and has higher priority than current - * * Must be called with lock->wait_lock held. + * + * @lock: the lock to be acquired. + * @task: the task which wants to acquire the lock + * @waiter: the waiter that is queued to the lock's wait list. (could be NULL) */ -static int try_to_take_rt_mutex(struct rt_mutex *lock) +static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, + struct rt_mutex_waiter *waiter) { /* * We have to be careful here if the atomic speedups are @@ -390,15 +331,52 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock) */ mark_rt_mutex_waiters(lock); - if (rt_mutex_owner(lock) && !try_to_steal_lock(lock, current)) + if (rt_mutex_owner(lock)) return 0; + /* + * It will get the lock because of one of these conditions: + * 1) there is no waiter + * 2) higher priority than waiters + * 3) it is top waiter + */ + if (rt_mutex_has_waiters(lock)) { + if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) { + if (!waiter || waiter != rt_mutex_top_waiter(lock)) + return 0; + } + } + + if (waiter || rt_mutex_has_waiters(lock)) { + unsigned long flags; + struct rt_mutex_waiter *top; + + raw_spin_lock_irqsave(&task->pi_lock, flags); + + /* remove the queued waiter. */ + if (waiter) { + plist_del(&waiter->list_entry, &lock->wait_list); + task->pi_blocked_on = NULL; + } + + /* + * We have to enqueue the top waiter(if it exists) into + * task->pi_waiters list. + */ + if (rt_mutex_has_waiters(lock)) { + top = rt_mutex_top_waiter(lock); + top->pi_list_entry.prio = top->list_entry.prio; + plist_add(&top->pi_list_entry, &task->pi_waiters); + } + raw_spin_unlock_irqrestore(&task->pi_lock, flags); + } + /* We got the lock. */ debug_rt_mutex_lock(lock); - rt_mutex_set_owner(lock, current, 0); + rt_mutex_set_owner(lock, task); - rt_mutex_deadlock_account_lock(lock, current); + rt_mutex_deadlock_account_lock(lock, task); return 1; } @@ -436,6 +414,9 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, raw_spin_unlock_irqrestore(&task->pi_lock, flags); + if (!owner) + return 0; + 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); @@ -472,21 +453,18 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, /* * Wake up the next waiter on the lock. * - * Remove the top waiter from the current tasks waiter list and from - * the lock waiter list. Set it as pending owner. Then wake it up. + * Remove the top waiter from the current tasks waiter list and wake it up. * * Called with lock->wait_lock held. */ static void wakeup_next_waiter(struct rt_mutex *lock) { struct rt_mutex_waiter *waiter; - struct task_struct *pendowner; unsigned long flags; raw_spin_lock_irqsave(¤t->pi_lock, flags); waiter = rt_mutex_top_waiter(lock); - plist_del(&waiter->list_entry, &lock->wait_list); /* * Remove it from current->pi_waiters. We do not adjust a @@ -495,43 +473,19 @@ static void wakeup_next_waiter(struct rt_mutex *lock) * lock->wait_lock. */ plist_del(&waiter->pi_list_entry, ¤t->pi_waiters); - pendowner = waiter->task; - waiter->task = NULL; - rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING); + rt_mutex_set_owner(lock, NULL); raw_spin_unlock_irqrestore(¤t->pi_lock, flags); - /* - * Clear the pi_blocked_on variable and enqueue a possible - * waiter into the pi_waiters list of the pending owner. This - * prevents that in case the pending owner gets unboosted a - * waiter with higher priority than pending-owner->normal_prio - * is blocked on the unboosted (pending) owner. - */ - raw_spin_lock_irqsave(&pendowner->pi_lock, flags); - - WARN_ON(!pendowner->pi_blocked_on); - WARN_ON(pendowner->pi_blocked_on != waiter); - WARN_ON(pendowner->pi_blocked_on->lock != lock); - - pendowner->pi_blocked_on = NULL; - - if (rt_mutex_has_waiters(lock)) { - struct rt_mutex_waiter *next; - - next = rt_mutex_top_waiter(lock); - plist_add(&next->pi_list_entry, &pendowner->pi_waiters); - } - raw_spin_unlock_irqrestore(&pendowner->pi_lock, flags); - - wake_up_process(pendowner); + wake_up_process(waiter->task); } /* - * Remove a waiter from a lock + * Remove a waiter from a lock and give up * - * Must be called with lock->wait_lock held + * Must be called with lock->wait_lock held and + * have just failed to try_to_take_rt_mutex(). */ static void remove_waiter(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) @@ -543,11 +497,13 @@ static void remove_waiter(struct rt_mutex *lock, raw_spin_lock_irqsave(¤t->pi_lock, flags); plist_del(&waiter->list_entry, &lock->wait_list); - waiter->task = NULL; current->pi_blocked_on = NULL; raw_spin_unlock_irqrestore(¤t->pi_lock, flags); - if (first && owner != current) { + if (!owner) + return; + + if (first) { raw_spin_lock_irqsave(&owner->pi_lock, flags); @@ -614,21 +570,19 @@ void rt_mutex_adjust_pi(struct task_struct *task) * or TASK_UNINTERRUPTIBLE) * @timeout: the pre-initialized and started timer, or NULL for none * @waiter: the pre-initialized rt_mutex_waiter - * @detect_deadlock: passed to task_blocks_on_rt_mutex * * lock->wait_lock must be held by the caller. */ static int __sched __rt_mutex_slowlock(struct rt_mutex *lock, int state, struct hrtimer_sleeper *timeout, - struct rt_mutex_waiter *waiter, - int detect_deadlock) + struct rt_mutex_waiter *waiter) { int ret = 0; for (;;) { /* Try to acquire the lock: */ - if (try_to_take_rt_mutex(lock)) + if (try_to_take_rt_mutex(lock, current, waiter)) break; /* @@ -645,39 +599,11 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, break; } - /* - * waiter->task is NULL the first time we come here and - * when we have been woken up by the previous owner - * but the lock got stolen by a higher prio task. - */ - if (!waiter->task) { - ret = task_blocks_on_rt_mutex(lock, waiter, current, - detect_deadlock); - /* - * If we got woken up by the owner then start loop - * all over without going into schedule to try - * to get the lock now: - */ - if (unlikely(!waiter->task)) { - /* - * Reset the return value. We might - * have returned with -EDEADLK and the - * owner released the lock while we - * were walking the pi chain. - */ - ret = 0; - continue; - } - if (unlikely(ret)) - break; - } - raw_spin_unlock(&lock->wait_lock); debug_rt_mutex_print_deadlock(waiter); - if (waiter->task) - schedule_rt_mutex(lock); + schedule_rt_mutex(lock); raw_spin_lock(&lock->wait_lock); set_current_state(state); @@ -698,12 +624,11 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, int ret = 0; debug_rt_mutex_init_waiter(&waiter); - waiter.task = NULL; raw_spin_lock(&lock->wait_lock); /* Try to acquire the lock again: */ - if (try_to_take_rt_mutex(lock)) { + if (try_to_take_rt_mutex(lock, current, NULL)) { raw_spin_unlock(&lock->wait_lock); return 0; } @@ -717,12 +642,14 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, timeout->task = NULL; } - ret = __rt_mutex_slowlock(lock, state, timeout, &waiter, - detect_deadlock); + ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock); + + if (likely(!ret)) + ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); set_current_state(TASK_RUNNING); - if (unlikely(waiter.task)) + if (unlikely(ret)) remove_waiter(lock, &waiter); /* @@ -737,14 +664,6 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, if (unlikely(timeout)) hrtimer_cancel(&timeout->timer); - /* - * Readjust priority, when we did not get the lock. We might - * have been the pending owner and boosted. Since we did not - * take the lock, the PI boost has to go. - */ - if (unlikely(ret)) - rt_mutex_adjust_prio(current); - debug_rt_mutex_free_waiter(&waiter); return ret; @@ -762,7 +681,7 @@ rt_mutex_slowtrylock(struct rt_mutex *lock) if (likely(rt_mutex_owner(lock) != current)) { - ret = try_to_take_rt_mutex(lock); + ret = try_to_take_rt_mutex(lock, current, NULL); /* * try_to_take_rt_mutex() sets the lock waiters * bit unconditionally. Clean this up. @@ -992,7 +911,7 @@ void rt_mutex_init_proxy_locked(struct rt_mutex *lock, { __rt_mutex_init(lock, NULL); debug_rt_mutex_proxy_lock(lock, proxy_owner); - rt_mutex_set_owner(lock, proxy_owner, 0); + rt_mutex_set_owner(lock, proxy_owner); rt_mutex_deadlock_account_lock(lock, proxy_owner); } @@ -1008,7 +927,7 @@ void rt_mutex_proxy_unlock(struct rt_mutex *lock, struct task_struct *proxy_owner) { debug_rt_mutex_proxy_unlock(lock); - rt_mutex_set_owner(lock, NULL, 0); + rt_mutex_set_owner(lock, NULL); rt_mutex_deadlock_account_unlock(proxy_owner); } @@ -1034,20 +953,14 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock, raw_spin_lock(&lock->wait_lock); - mark_rt_mutex_waiters(lock); - - if (!rt_mutex_owner(lock) || try_to_steal_lock(lock, task)) { - /* We got the lock for task. */ - debug_rt_mutex_lock(lock); - rt_mutex_set_owner(lock, task, 0); + if (try_to_take_rt_mutex(lock, task, NULL)) { raw_spin_unlock(&lock->wait_lock); - rt_mutex_deadlock_account_lock(lock, task); return 1; } ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock); - if (ret && !waiter->task) { + if (ret && !rt_mutex_owner(lock)) { /* * Reset the return value. We might have * returned with -EDEADLK and the owner @@ -1056,6 +969,10 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock, */ ret = 0; } + + if (unlikely(ret)) + remove_waiter(lock, waiter); + raw_spin_unlock(&lock->wait_lock); debug_rt_mutex_print_deadlock(waiter); @@ -1110,12 +1027,11 @@ int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, set_current_state(TASK_INTERRUPTIBLE); - ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter, - detect_deadlock); + ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); set_current_state(TASK_RUNNING); - if (unlikely(waiter->task)) + if (unlikely(ret)) remove_waiter(lock, waiter); /* @@ -1126,13 +1042,5 @@ int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, raw_spin_unlock(&lock->wait_lock); - /* - * Readjust priority, when we did not get the lock. We might have been - * the pending owner and boosted. Since we did not take the lock, the - * PI boost has to go. - */ - if (unlikely(ret)) - rt_mutex_adjust_prio(current); - return ret; } diff --git a/kernel/rtmutex_common.h b/kernel/rtmutex_common.h index 97a2f81866af..53a66c85261b 100644 --- a/kernel/rtmutex_common.h +++ b/kernel/rtmutex_common.h @@ -91,9 +91,8 @@ task_top_pi_waiter(struct task_struct *p) /* * lock->owner state tracking: */ -#define RT_MUTEX_OWNER_PENDING 1UL -#define RT_MUTEX_HAS_WAITERS 2UL -#define RT_MUTEX_OWNER_MASKALL 3UL +#define RT_MUTEX_HAS_WAITERS 1UL +#define RT_MUTEX_OWNER_MASKALL 1UL static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) { @@ -101,17 +100,6 @@ static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) ((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL); } -static inline struct task_struct *rt_mutex_real_owner(struct rt_mutex *lock) -{ - return (struct task_struct *) - ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); -} - -static inline unsigned long rt_mutex_owner_pending(struct rt_mutex *lock) -{ - return (unsigned long)lock->owner & RT_MUTEX_OWNER_PENDING; -} - /* * PI-futex support (proxy locking functions, etc.): */ -- cgit v1.2.3 From 48228f7b470a74b6469a250d2977a13128d8fe96 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 8 Feb 2011 12:39:54 -0500 Subject: lockdep/timers: Explain in detail the locking problems del_timer_sync() may cause Twice I had to explain the output about why lockdep gives an error with locks in IRQ context and with del_timer_sync(). Might as well write it up and place it in the comments above the code in del_timer_sync(). Perhaps the next time this lockdep dump triggers people will understand the issues. It is a ticky issue and very subtle, explaining it in detail in the code may help others understand the issue when they stumble upon the bug again. Signed-off-by: Steven Rostedt Signed-off-by: Peter Zijlstra LKML-Reference: <1297186794.23343.19.camel@gandalf.stny.rr.com> Signed-off-by: Ingo Molnar --- kernel/timer.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'kernel') diff --git a/kernel/timer.c b/kernel/timer.c index d6459923d245..5f40c2e0a94e 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -964,6 +964,25 @@ EXPORT_SYMBOL(try_to_del_timer_sync); * add_timer_on(). Upon exit the timer is not queued and the handler is * not running on any CPU. * + * Note: You must not hold locks that are held in interrupt context + * while calling this function. Even if the lock has nothing to do + * with the timer in question. Here's why: + * + * CPU0 CPU1 + * ---- ---- + * + * call_timer_fn(); + * base->running_timer = mytimer; + * spin_lock_irq(somelock); + * + * spin_lock(somelock); + * del_timer_sync(mytimer); + * while (base->running_timer == mytimer); + * + * Now del_timer_sync() will never return and never release somelock. + * The interrupt on the other CPU is waiting to grab somelock but + * it has interrupted the softirq that CPU0 is waiting to finish. + * * The function returns whether it has deactivated a pending timer or not. */ int del_timer_sync(struct timer_list *timer) @@ -971,6 +990,10 @@ int del_timer_sync(struct timer_list *timer) #ifdef CONFIG_LOCKDEP unsigned long flags; + /* + * If lockdep gives a backtrace here, please reference + * the synchronization rules above. + */ local_irq_save(flags); lock_map_acquire(&timer->lockdep_map); lock_map_release(&timer->lockdep_map); -- cgit v1.2.3 From dbebbfbb1605f0179e7c0d900d941cc9c45de569 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 22 Feb 2011 21:46:25 +0100 Subject: rtmutex: tester: Remove the remaining BKL leftovers We just leave the numbers assinged as commemoration and in case that someone was crazy enough to reimplement the test stuff out of tree. Signed-off-by: Thomas Gleixner --- kernel/rtmutex-tester.c | 5 ++--- scripts/rt-tester/rt-tester.py | 2 -- scripts/rt-tester/t2-l1-2rt-sameprio.tst | 5 ----- scripts/rt-tester/t2-l1-pi.tst | 5 ----- scripts/rt-tester/t2-l1-signal.tst | 5 ----- scripts/rt-tester/t2-l2-2rt-deadlock.tst | 5 ----- scripts/rt-tester/t3-l1-pi-1rt.tst | 5 ----- scripts/rt-tester/t3-l1-pi-2rt.tst | 5 ----- scripts/rt-tester/t3-l1-pi-3rt.tst | 5 ----- scripts/rt-tester/t3-l1-pi-signal.tst | 5 ----- scripts/rt-tester/t3-l1-pi-steal.tst | 5 ----- scripts/rt-tester/t3-l2-pi.tst | 5 ----- scripts/rt-tester/t4-l2-pi-deboost.tst | 5 ----- scripts/rt-tester/t5-l4-pi-boost-deboost-setsched.tst | 5 ----- scripts/rt-tester/t5-l4-pi-boost-deboost.tst | 5 ----- 15 files changed, 2 insertions(+), 70 deletions(-) (limited to 'kernel') diff --git a/kernel/rtmutex-tester.c b/kernel/rtmutex-tester.c index d5b543506cbc..5c9ccd380966 100644 --- a/kernel/rtmutex-tester.c +++ b/kernel/rtmutex-tester.c @@ -44,9 +44,8 @@ enum test_opcodes { RTTEST_LOCKINTNOWAIT, /* 6 Lock interruptible no wait in wakeup, data = lockindex */ RTTEST_LOCKCONT, /* 7 Continue locking after the wakeup delay */ RTTEST_UNLOCK, /* 8 Unlock, data = lockindex */ - RTTEST_LOCKBKL, /* 9 Was: Lock BKL */ - RTTEST_UNLOCKBKL, /* 10 Was: Unlock BKL */ - RTTEST_SIGNAL, /* 11 Signal other test thread, data = thread id */ + /* 9, 10 - reserved for BKL commemoration */ + RTTEST_SIGNAL = 11, /* 11 Signal other test thread, data = thread id */ RTTEST_RESETEVENT = 98, /* 98 Reset event counter */ RTTEST_RESET = 99, /* 99 Reset all pending operations */ }; diff --git a/scripts/rt-tester/rt-tester.py b/scripts/rt-tester/rt-tester.py index 44423b4dcb82..8c81d76959ee 100644 --- a/scripts/rt-tester/rt-tester.py +++ b/scripts/rt-tester/rt-tester.py @@ -33,8 +33,6 @@ cmd_opcodes = { "lockintnowait" : "6", "lockcont" : "7", "unlock" : "8", - "lockbkl" : "9", - "unlockbkl" : "10", "signal" : "11", "resetevent" : "98", "reset" : "99", diff --git a/scripts/rt-tester/t2-l1-2rt-sameprio.tst b/scripts/rt-tester/t2-l1-2rt-sameprio.tst index 8821f27cc8be..3710c8b2090d 100644 --- a/scripts/rt-tester/t2-l1-2rt-sameprio.tst +++ b/scripts/rt-tester/t2-l1-2rt-sameprio.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal 0 # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t2-l1-pi.tst b/scripts/rt-tester/t2-l1-pi.tst index cde1f189a02b..b4cc95975adb 100644 --- a/scripts/rt-tester/t2-l1-pi.tst +++ b/scripts/rt-tester/t2-l1-pi.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal 0 # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t2-l1-signal.tst b/scripts/rt-tester/t2-l1-signal.tst index 3ab0bfc49950..1b57376cc1f7 100644 --- a/scripts/rt-tester/t2-l1-signal.tst +++ b/scripts/rt-tester/t2-l1-signal.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal 0 # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t2-l2-2rt-deadlock.tst b/scripts/rt-tester/t2-l2-2rt-deadlock.tst index f4b5d5d6215f..68b10629b6f4 100644 --- a/scripts/rt-tester/t2-l2-2rt-deadlock.tst +++ b/scripts/rt-tester/t2-l2-2rt-deadlock.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal 0 # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t3-l1-pi-1rt.tst b/scripts/rt-tester/t3-l1-pi-1rt.tst index 63440ca2cce9..8e6c8b11ae56 100644 --- a/scripts/rt-tester/t3-l1-pi-1rt.tst +++ b/scripts/rt-tester/t3-l1-pi-1rt.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t3-l1-pi-2rt.tst b/scripts/rt-tester/t3-l1-pi-2rt.tst index e5816fe67df3..69c2212fc520 100644 --- a/scripts/rt-tester/t3-l1-pi-2rt.tst +++ b/scripts/rt-tester/t3-l1-pi-2rt.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t3-l1-pi-3rt.tst b/scripts/rt-tester/t3-l1-pi-3rt.tst index 718b82b5d3bb..9b0f1eb26a88 100644 --- a/scripts/rt-tester/t3-l1-pi-3rt.tst +++ b/scripts/rt-tester/t3-l1-pi-3rt.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t3-l1-pi-signal.tst b/scripts/rt-tester/t3-l1-pi-signal.tst index c6e213563498..39ec74ab06ee 100644 --- a/scripts/rt-tester/t3-l1-pi-signal.tst +++ b/scripts/rt-tester/t3-l1-pi-signal.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t3-l1-pi-steal.tst b/scripts/rt-tester/t3-l1-pi-steal.tst index f53749d59d79..e03db7e010fa 100644 --- a/scripts/rt-tester/t3-l1-pi-steal.tst +++ b/scripts/rt-tester/t3-l1-pi-steal.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t3-l2-pi.tst b/scripts/rt-tester/t3-l2-pi.tst index cdc3e4fd7bac..7b59100d3e48 100644 --- a/scripts/rt-tester/t3-l2-pi.tst +++ b/scripts/rt-tester/t3-l2-pi.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t4-l2-pi-deboost.tst b/scripts/rt-tester/t4-l2-pi-deboost.tst index baa14137f473..2f0e049d6443 100644 --- a/scripts/rt-tester/t4-l2-pi-deboost.tst +++ b/scripts/rt-tester/t4-l2-pi-deboost.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t5-l4-pi-boost-deboost-setsched.tst b/scripts/rt-tester/t5-l4-pi-boost-deboost-setsched.tst index e6ec0c81b54d..04f4034ff895 100644 --- a/scripts/rt-tester/t5-l4-pi-boost-deboost-setsched.tst +++ b/scripts/rt-tester/t5-l4-pi-boost-deboost-setsched.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number diff --git a/scripts/rt-tester/t5-l4-pi-boost-deboost.tst b/scripts/rt-tester/t5-l4-pi-boost-deboost.tst index ca64f8bbf4bc..a48a6ee29ddc 100644 --- a/scripts/rt-tester/t5-l4-pi-boost-deboost.tst +++ b/scripts/rt-tester/t5-l4-pi-boost-deboost.tst @@ -19,8 +19,6 @@ # lockintnowait lock nr (0-7) # lockcont lock nr (0-7) # unlock lock nr (0-7) -# lockbkl lock nr (0-7) -# unlockbkl lock nr (0-7) # signal thread to signal (0-7) # reset 0 # resetevent 0 @@ -39,9 +37,6 @@ # blocked lock nr (0-7) # blockedwake lock nr (0-7) # unlocked lock nr (0-7) -# lockedbkl dont care -# blockedbkl dont care -# unlockedbkl dont care # opcodeeq command opcode or number # opcodelt number # opcodegt number -- cgit v1.2.3