3.12.38-rt53-rc1 stable review patch. If anyone has any objections, please let me know.
------------------ From: Thomas Gleixner <t...@linutronix.de> upstream commit: 8930ed80f970a90a795239e7415c9b0e6f964649 The conditions under which deadlock detection is conducted are unclear and undocumented. Add constants instead of using 0/1 and provide a selection function which hides the additional debug dependency from the calling code. Add comments where needed. Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: Peter Zijlstra <pet...@infradead.org> Reviewed-by: Steven Rostedt <rost...@goodmis.org> Cc: Lai Jiangshan <la...@cn.fujitsu.com> Link: http://lkml.kernel.org/r/20140522031949.947264...@linutronix.de Signed-off-by: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Steven Rostedt <rost...@goodmis.org> Conflicts: kernel/rtmutex.c --- kernel/rtmutex-debug.c | 5 +-- kernel/rtmutex-debug.h | 7 +++-- kernel/rtmutex.c | 82 ++++++++++++++++++++++++++++++++++--------------- kernel/rtmutex.h | 7 ++++- kernel/rtmutex_common.h | 15 +++++++++ 5 files changed, 85 insertions(+), 31 deletions(-) diff --git a/kernel/rtmutex-debug.c b/kernel/rtmutex-debug.c index 13b243a323fa..2035a46ca489 100644 --- a/kernel/rtmutex-debug.c +++ b/kernel/rtmutex-debug.c @@ -66,12 +66,13 @@ void rt_mutex_debug_task_free(struct task_struct *task) * the deadlock. We print when we return. act_waiter can be NULL in * case of a remove waiter operation. */ -void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter, +void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk, + struct rt_mutex_waiter *act_waiter, struct rt_mutex *lock) { struct task_struct *task; - if (!debug_locks || detect || !act_waiter) + if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter) return; task = rt_mutex_owner(act_waiter->lock); diff --git a/kernel/rtmutex-debug.h b/kernel/rtmutex-debug.h index ab29b6a22669..d0519c3432b6 100644 --- a/kernel/rtmutex-debug.h +++ b/kernel/rtmutex-debug.h @@ -20,14 +20,15 @@ extern void debug_rt_mutex_unlock(struct rt_mutex *lock); extern void debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner); extern void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock); -extern void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *waiter, +extern void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk, + struct rt_mutex_waiter *waiter, struct rt_mutex *lock); extern void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter); # define debug_rt_mutex_reset_waiter(w) \ do { (w)->deadlock_lock = NULL; } while (0) -static inline int debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter, - int detect) +static inline bool debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter, + enum rtmutex_chainwalk walk) { return (waiter != NULL); } diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index 7a788794bfb6..8f4a8188d6e3 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -254,6 +254,32 @@ static void rt_mutex_wake_waiter(struct rt_mutex_waiter *waiter) } /* + * Deadlock detection is conditional: + * + * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted + * if the detect argument is == RT_MUTEX_FULL_CHAINWALK. + * + * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always + * conducted independent of the detect argument. + * + * If the waiter argument is NULL this indicates the deboost path and + * deadlock detection is disabled independent of the detect argument + * and the config settings. + */ +static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter, + enum rtmutex_chainwalk chwalk) +{ + /* + * This is just a wrapper function for the following call, + * because debug_rt_mutex_detect_deadlock() smells like a magic + * debug feature and I wanted to keep the cond function in the + * main source file along with the comments instead of having + * two of the same in the headers. + */ + return debug_rt_mutex_detect_deadlock(waiter, chwalk); +} + +/* * Max number of times we'll walk the boosting chain: */ int max_lock_depth = 1024; @@ -328,7 +354,7 @@ static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) * goto again; */ static int rt_mutex_adjust_prio_chain(struct task_struct *task, - int deadlock_detect, + enum rtmutex_chainwalk chwalk, struct rt_mutex *orig_lock, struct rt_mutex *next_lock, struct rt_mutex_waiter *orig_waiter, @@ -336,12 +362,12 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, { struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; struct rt_mutex_waiter *prerequeue_top_waiter; - int detect_deadlock, ret = 0, depth = 0; + int ret = 0, depth = 0; struct rt_mutex *lock; + bool detect_deadlock; unsigned long flags; - detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, - deadlock_detect); + detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk); /* * The (de)boosting is a step by step approach with a lot of @@ -467,7 +493,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, * walk, we detected a deadlock. */ if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { - debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); + debug_rt_mutex_deadlock(chwalk, orig_waiter, lock); raw_spin_unlock(&lock->wait_lock); ret = -EDEADLK; goto out_unlock_pi; @@ -763,7 +789,7 @@ try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, static int task_blocks_on_rt_mutex(struct rt_mutex *lock, struct rt_mutex_waiter *waiter, struct task_struct *task, - int detect_deadlock) + enum rtmutex_chainwalk chwalk) { struct task_struct *owner = rt_mutex_owner(lock); struct rt_mutex_waiter *top_waiter = waiter; @@ -827,7 +853,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, __rt_mutex_adjust_prio(owner); if (rt_mutex_real_waiter(owner->pi_blocked_on)) chain_walk = 1; - } else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) { + } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) { chain_walk = 1; } @@ -852,7 +878,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, raw_spin_unlock(&lock->wait_lock); - res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, + res = rt_mutex_adjust_prio_chain(owner, chwalk, lock, next_lock, waiter, task); raw_spin_lock(&lock->wait_lock); @@ -960,7 +986,8 @@ static void remove_waiter(struct rt_mutex *lock, raw_spin_unlock(&lock->wait_lock); - rt_mutex_adjust_prio_chain(owner, 0, lock, next_lock, NULL, current); + rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, + next_lock, NULL, current); raw_spin_lock(&lock->wait_lock); } @@ -989,8 +1016,8 @@ void rt_mutex_adjust_pi(struct task_struct *task) /* gets dropped in rt_mutex_adjust_prio_chain()! */ get_task_struct(task); raw_spin_unlock_irqrestore(&task->pi_lock, flags); - - rt_mutex_adjust_prio_chain(task, 0, NULL, next_lock, NULL, task); + rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL, + next_lock, NULL, task); } #ifdef CONFIG_PREEMPT_RT_FULL @@ -1499,7 +1526,8 @@ static void rt_mutex_handle_deadlock(int res, int detect_deadlock, static int __sched rt_mutex_slowlock(struct rt_mutex *lock, int state, struct hrtimer_sleeper *timeout, - int detect_deadlock, struct ww_acquire_ctx *ww_ctx) + enum rtmutex_chainwalk chwalk, + struct ww_acquire_ctx *ww_ctx) { struct rt_mutex_waiter waiter; int ret = 0; @@ -1526,7 +1554,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, timeout->task = NULL; } - ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock); + ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk); if (likely(!ret)) ret = __rt_mutex_slowlock(lock, state, timeout, &waiter, ww_ctx); @@ -1535,8 +1563,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, if (unlikely(ret)) { remove_waiter(lock, &waiter); - rt_mutex_handle_deadlock(ret, detect_deadlock, &waiter); - + rt_mutex_handle_deadlock(ret, chwalk, &waiter); } else if (ww_ctx) { ww_mutex_account_lock(lock, ww_ctx); } @@ -1668,30 +1695,32 @@ rt_mutex_fastlock(struct rt_mutex *lock, int state, struct ww_acquire_ctx *ww_ctx, int (*slowfn)(struct rt_mutex *lock, int state, struct hrtimer_sleeper *timeout, - int detect_deadlock, + enum rtmutex_chainwalk chwalk, struct ww_acquire_ctx *ww_ctx)) { if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { rt_mutex_deadlock_account_lock(lock, current); return 0; } else - return slowfn(lock, state, NULL, 0, ww_ctx); + return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK, ww_ctx); } static inline int rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, - struct hrtimer_sleeper *timeout, int detect_deadlock, + struct hrtimer_sleeper *timeout, + enum rtmutex_chainwalk chwalk, struct ww_acquire_ctx *ww_ctx, int (*slowfn)(struct rt_mutex *lock, int state, struct hrtimer_sleeper *timeout, - int detect_deadlock, + enum rtmutex_chainwalk chwalk, struct ww_acquire_ctx *ww_ctx)) { - if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { + if (chwalk == RT_MUTEX_MIN_CHAINWALK && + likely(rt_mutex_cmpxchg(lock, NULL, current))) { rt_mutex_deadlock_account_lock(lock, current); return 0; } else - return slowfn(lock, state, timeout, detect_deadlock, ww_ctx); + return slowfn(lock, state, timeout, chwalk, ww_ctx); } static inline int @@ -1753,8 +1782,9 @@ int rt_mutex_timed_futex_lock(struct rt_mutex *lock, { might_sleep(); - return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 1, - NULL, rt_mutex_slowlock); + return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, + RT_MUTEX_FULL_CHAINWALK, NULL, + rt_mutex_slowlock); } /** @@ -1794,7 +1824,8 @@ rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout) { might_sleep(); - return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 0, + return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, + RT_MUTEX_MIN_CHAINWALK, NULL, rt_mutex_slowlock); } EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); @@ -1950,7 +1981,8 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock, #endif /* We enforce deadlock detection for futexes */ - ret = task_blocks_on_rt_mutex(lock, waiter, task, 1); + ret = task_blocks_on_rt_mutex(lock, waiter, task, + RT_MUTEX_FULL_CHAINWALK); if (ret && !rt_mutex_owner(lock)) { /* diff --git a/kernel/rtmutex.h b/kernel/rtmutex.h index f6a1f3c133b1..c4060584c407 100644 --- a/kernel/rtmutex.h +++ b/kernel/rtmutex.h @@ -22,10 +22,15 @@ #define debug_rt_mutex_init(m, n) do { } while (0) #define debug_rt_mutex_deadlock(d, a ,l) do { } while (0) #define debug_rt_mutex_print_deadlock(w) do { } while (0) -#define debug_rt_mutex_detect_deadlock(w,d) (d) #define debug_rt_mutex_reset_waiter(w) do { } while (0) static inline void rt_mutex_print_deadlock(struct rt_mutex_waiter *w) { WARN(1, "rtmutex deadlock detected\n"); } + +static inline bool debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *w, + enum rtmutex_chainwalk walk) +{ + return walk == RT_MUTEX_FULL_CHAINWALK; +} diff --git a/kernel/rtmutex_common.h b/kernel/rtmutex_common.h index efde34108ebc..213c7bf3c0d9 100644 --- a/kernel/rtmutex_common.h +++ b/kernel/rtmutex_common.h @@ -102,6 +102,21 @@ static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) } /* + * Constants for rt mutex functions which have a selectable deadlock + * detection. + * + * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are + * no further PI adjustments to be made. + * + * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full + * walk of the lock chain. + */ +enum rtmutex_chainwalk { + RT_MUTEX_MIN_CHAINWALK, + RT_MUTEX_FULL_CHAINWALK, +}; + +/* * PI-futex support (proxy locking functions, etc.): */ #define PI_WAKEUP_INPROGRESS ((struct rt_mutex_waiter *) 1) -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
