path: root/debian/patches-rt/0176-locking-rtmutex-add-ww_mutex-addon-for-mutex-rt.patch

From 9b2b99d3a96fd3eb164a6f1993effe944ced9e40 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 12 Oct 2017 17:34:38 +0200
Subject: [PATCH 176/323] locking/rtmutex: add ww_mutex addon for mutex-rt
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.215-rt107.tar.xz

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/mutex.h           |   8 -
 include/linux/ww_mutex.h        |   8 +
 kernel/locking/rtmutex.c        | 262 ++++++++++++++++++++++++++++++--
 kernel/locking/rtmutex_common.h |   2 +
 kernel/locking/rwsem-rt.c       |   2 +-
 5 files changed, 262 insertions(+), 20 deletions(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index e45774a337d2c..90923d3008fcd 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -82,14 +82,6 @@ struct mutex {
 struct ww_class;
 struct ww_acquire_ctx;
 
-struct ww_mutex {
-	struct mutex base;
-	struct ww_acquire_ctx *ctx;
-#ifdef CONFIG_DEBUG_MUTEXES
-	struct ww_class *ww_class;
-#endif
-};
-
 /*
  * This is the control structure for tasks blocked on mutex,
  * which resides on the blocked task's kernel stack:
diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
index 6ecf2a0220dbe..3145de5986450 100644
--- a/include/linux/ww_mutex.h
+++ b/include/linux/ww_mutex.h
@@ -28,6 +28,14 @@ struct ww_class {
 	unsigned int is_wait_die;
 };
 
+struct ww_mutex {
+	struct mutex base;
+	struct ww_acquire_ctx *ctx;
+#ifdef CONFIG_DEBUG_MUTEXES
+	struct ww_class *ww_class;
+#endif
+};
+
 struct ww_acquire_ctx {
 	struct task_struct *task;
 	unsigned long stamp;
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 1bf7a04688c54..c095d1b92f702 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -24,6 +24,7 @@
 #include <linux/sched/wake_q.h>
 #include <linux/sched/debug.h>
 #include <linux/timer.h>
+#include <linux/ww_mutex.h>
 
 #include "rtmutex_common.h"
 
@@ -1234,6 +1235,40 @@ EXPORT_SYMBOL(__rt_spin_lock_init);
 
 #endif /* PREEMPT_RT */
 
+#ifdef CONFIG_PREEMPT_RT
+	static inline int __sched
+__mutex_lock_check_stamp(struct rt_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+	struct ww_mutex *ww = container_of(lock, struct ww_mutex, base.lock);
+	struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
+
+	if (!hold_ctx)
+		return 0;
+
+	if (unlikely(ctx == hold_ctx))
+		return -EALREADY;
+
+	if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
+	    (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
+#ifdef CONFIG_DEBUG_MUTEXES
+		DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
+		ctx->contending_lock = ww;
+#endif
+		return -EDEADLK;
+	}
+
+	return 0;
+}
+#else
+	static inline int __sched
+__mutex_lock_check_stamp(struct rt_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+	BUG();
+	return 0;
+}
+
+#endif
+
 static inline int
 try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
 		     struct rt_mutex_waiter *waiter)
@@ -1512,7 +1547,8 @@ void rt_mutex_init_waiter(struct rt_mutex_waiter *waiter, bool savestate)
 static int __sched
 __rt_mutex_slowlock(struct rt_mutex *lock, int state,
 		    struct hrtimer_sleeper *timeout,
-		    struct rt_mutex_waiter *waiter)
+		    struct rt_mutex_waiter *waiter,
+		    struct ww_acquire_ctx *ww_ctx)
 {
 	int ret = 0;
 
@@ -1530,6 +1566,12 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state,
 			break;
 		}
 
+		if (ww_ctx && ww_ctx->acquired > 0) {
+			ret = __mutex_lock_check_stamp(lock, ww_ctx);
+			if (ret)
+				break;
+		}
+
 		raw_spin_unlock_irq(&lock->wait_lock);
 
 		schedule();
@@ -1558,16 +1600,106 @@ static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
 	}
 }
 
+static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
+						   struct ww_acquire_ctx *ww_ctx)
+{
+#ifdef CONFIG_DEBUG_MUTEXES
+	/*
+	 * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
+	 * but released with a normal mutex_unlock in this call.
+	 *
+	 * This should never happen, always use ww_mutex_unlock.
+	 */
+	DEBUG_LOCKS_WARN_ON(ww->ctx);
+
+	/*
+	 * Not quite done after calling ww_acquire_done() ?
+	 */
+	DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
+
+	if (ww_ctx->contending_lock) {
+		/*
+		 * After -EDEADLK you tried to
+		 * acquire a different ww_mutex? Bad!
+		 */
+		DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
+
+		/*
+		 * You called ww_mutex_lock after receiving -EDEADLK,
+		 * but 'forgot' to unlock everything else first?
+		 */
+		DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
+		ww_ctx->contending_lock = NULL;
+	}
+
+	/*
+	 * Naughty, using a different class will lead to undefined behavior!
+	 */
+	DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
+#endif
+	ww_ctx->acquired++;
+}
+
+#ifdef CONFIG_PREEMPT_RT
+static void ww_mutex_account_lock(struct rt_mutex *lock,
+				  struct ww_acquire_ctx *ww_ctx)
+{
+	struct ww_mutex *ww = container_of(lock, struct ww_mutex, base.lock);
+	struct rt_mutex_waiter *waiter, *n;
+
+	/*
+	 * This branch gets optimized out for the common case,
+	 * and is only important for ww_mutex_lock.
+	 */
+	ww_mutex_lock_acquired(ww, ww_ctx);
+	ww->ctx = ww_ctx;
+
+	/*
+	 * Give any possible sleeping processes the chance to wake up,
+	 * so they can recheck if they have to back off.
+	 */
+	rbtree_postorder_for_each_entry_safe(waiter, n, &lock->waiters.rb_root,
+					     tree_entry) {
+		/* XXX debug rt mutex waiter wakeup */
+
+		BUG_ON(waiter->lock != lock);
+		rt_mutex_wake_waiter(waiter);
+	}
+}
+
+#else
+
+static void ww_mutex_account_lock(struct rt_mutex *lock,
+				  struct ww_acquire_ctx *ww_ctx)
+{
+	BUG();
+}
+#endif
+
 int __sched rt_mutex_slowlock_locked(struct rt_mutex *lock, int state,
 				     struct hrtimer_sleeper *timeout,
 				     enum rtmutex_chainwalk chwalk,
+				     struct ww_acquire_ctx *ww_ctx,
 				     struct rt_mutex_waiter *waiter)
 {
 	int ret;
 
+#ifdef CONFIG_PREEMPT_RT
+	if (ww_ctx) {
+		struct ww_mutex *ww;
+
+		ww = container_of(lock, struct ww_mutex, base.lock);
+		if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
+			return -EALREADY;
+	}
+#endif
+
 	/* Try to acquire the lock again: */
-	if (try_to_take_rt_mutex(lock, current, NULL))
+	if (try_to_take_rt_mutex(lock, current, NULL)) {
+		if (ww_ctx)
+			ww_mutex_account_lock(lock, ww_ctx);
 		return 0;
+	}
 
 	set_current_state(state);
 
@@ -1577,14 +1709,24 @@ int __sched rt_mutex_slowlock_locked(struct rt_mutex *lock, int state,
 
 	ret = task_blocks_on_rt_mutex(lock, waiter, current, chwalk);
 
-	if (likely(!ret))
+	if (likely(!ret)) {
 		/* sleep on the mutex */
-		ret = __rt_mutex_slowlock(lock, state, timeout, waiter);
+		ret = __rt_mutex_slowlock(lock, state, timeout, waiter,
+					  ww_ctx);
+	} else if (ww_ctx) {
+		/* ww_mutex received EDEADLK, let it become EALREADY */
+		ret = __mutex_lock_check_stamp(lock, ww_ctx);
+		BUG_ON(!ret);
+	}
 
 	if (unlikely(ret)) {
 		__set_current_state(TASK_RUNNING);
 		remove_waiter(lock, waiter);
-		rt_mutex_handle_deadlock(ret, chwalk, waiter);
+		/* ww_mutex wants to report EDEADLK/EALREADY, let it */
+		if (!ww_ctx)
+			rt_mutex_handle_deadlock(ret, chwalk, waiter);
+	} else if (ww_ctx) {
+		ww_mutex_account_lock(lock, ww_ctx);
 	}
 
 	/*
@@ -1601,7 +1743,8 @@ int __sched rt_mutex_slowlock_locked(struct rt_mutex *lock, int state,
 static int __sched
 rt_mutex_slowlock(struct rt_mutex *lock, int state,
 		  struct hrtimer_sleeper *timeout,
-		  enum rtmutex_chainwalk chwalk)
+		  enum rtmutex_chainwalk chwalk,
+		  struct ww_acquire_ctx *ww_ctx)
 {
 	struct rt_mutex_waiter waiter;
 	unsigned long flags;
@@ -1619,7 +1762,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 	 */
 	raw_spin_lock_irqsave(&lock->wait_lock, flags);
 
-	ret = rt_mutex_slowlock_locked(lock, state, timeout, chwalk, &waiter);
+	ret = rt_mutex_slowlock_locked(lock, state, timeout, chwalk, ww_ctx,
+				       &waiter);
 
 	raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
 
@@ -1749,14 +1893,16 @@ static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
  */
 static inline int
 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,
-				enum rtmutex_chainwalk chwalk))
+				enum rtmutex_chainwalk chwalk,
+				struct ww_acquire_ctx *ww_ctx))
 {
 	if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
 		return 0;
 
-	return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
+	return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK, ww_ctx);
 }
 
 static inline int
@@ -1801,7 +1947,7 @@ rt_mutex_fastunlock(struct rt_mutex *lock,
 int __sched __rt_mutex_lock_state(struct rt_mutex *lock, int state)
 {
 	might_sleep();
-	return rt_mutex_fastlock(lock, state, rt_mutex_slowlock);
+	return rt_mutex_fastlock(lock, state, NULL, rt_mutex_slowlock);
 }
 
 /**
@@ -2245,7 +2391,7 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock,
 	raw_spin_lock_irq(&lock->wait_lock);
 	/* sleep on the mutex */
 	set_current_state(TASK_INTERRUPTIBLE);
-	ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
+	ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter, NULL);
 	/*
 	 * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
 	 * have to fix that up.
@@ -2315,3 +2461,97 @@ bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
 
 	return cleanup;
 }
+
+static inline int
+ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
+	unsigned int tmp;
+
+	if (ctx->deadlock_inject_countdown-- == 0) {
+		tmp = ctx->deadlock_inject_interval;
+		if (tmp > UINT_MAX/4)
+			tmp = UINT_MAX;
+		else
+			tmp = tmp*2 + tmp + tmp/2;
+
+		ctx->deadlock_inject_interval = tmp;
+		ctx->deadlock_inject_countdown = tmp;
+		ctx->contending_lock = lock;
+
+		ww_mutex_unlock(lock);
+
+		return -EDEADLK;
+	}
+#endif
+
+	return 0;
+}
+
+#ifdef CONFIG_PREEMPT_RT
+int __sched
+ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+	int ret;
+
+	might_sleep();
+
+	mutex_acquire_nest(&lock->base.dep_map, 0, 0,
+			   ctx ? &ctx->dep_map : NULL, _RET_IP_);
+	ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL, 0,
+				ctx);
+	if (ret)
+		mutex_release(&lock->base.dep_map, _RET_IP_);
+	else if (!ret && ctx && ctx->acquired > 1)
+		return ww_mutex_deadlock_injection(lock, ctx);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible);
+
+int __sched
+ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+	int ret;
+
+	might_sleep();
+
+	mutex_acquire_nest(&lock->base.dep_map, 0, 0,
+			   ctx ? &ctx->dep_map : NULL, _RET_IP_);
+	ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL, 0,
+				ctx);
+	if (ret)
+		mutex_release(&lock->base.dep_map, _RET_IP_);
+	else if (!ret && ctx && ctx->acquired > 1)
+		return ww_mutex_deadlock_injection(lock, ctx);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ww_mutex_lock);
+
+void __sched ww_mutex_unlock(struct ww_mutex *lock)
+{
+	/*
+	 * The unlocking fastpath is the 0->1 transition from 'locked'
+	 * into 'unlocked' state:
+	 */
+	if (lock->ctx) {
+#ifdef CONFIG_DEBUG_MUTEXES
+		DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
+#endif
+		if (lock->ctx->acquired > 0)
+			lock->ctx->acquired--;
+		lock->ctx = NULL;
+	}
+
+	mutex_release(&lock->base.dep_map, _RET_IP_);
+	__rt_mutex_unlock(&lock->base.lock);
+}
+EXPORT_SYMBOL(ww_mutex_unlock);
+
+int __rt_mutex_owner_current(struct rt_mutex *lock)
+{
+	return rt_mutex_owner(lock) == current;
+}
+EXPORT_SYMBOL(__rt_mutex_owner_current);
+#endif
diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
index c1a280167e3cc..248a7d91583be 100644
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -159,6 +159,7 @@ extern void rt_mutex_postunlock(struct wake_q_head *wake_q,
 				struct wake_q_head *wake_sleeper_q);
 
 /* RW semaphore special interface */
+struct ww_acquire_ctx;
 
 extern int __rt_mutex_lock_state(struct rt_mutex *lock, int state);
 extern int __rt_mutex_trylock(struct rt_mutex *lock);
@@ -166,6 +167,7 @@ extern void __rt_mutex_unlock(struct rt_mutex *lock);
 int __sched rt_mutex_slowlock_locked(struct rt_mutex *lock, int state,
 				     struct hrtimer_sleeper *timeout,
 				     enum rtmutex_chainwalk chwalk,
+				     struct ww_acquire_ctx *ww_ctx,
 				     struct rt_mutex_waiter *waiter);
 void __sched rt_spin_lock_slowlock_locked(struct rt_mutex *lock,
 					  struct rt_mutex_waiter *waiter,
diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c
index a0771c150041e..274172d5bb3a5 100644
--- a/kernel/locking/rwsem-rt.c
+++ b/kernel/locking/rwsem-rt.c
@@ -138,7 +138,7 @@ static int __sched __down_read_common(struct rw_semaphore *sem, int state)
 	 */
 	rt_mutex_init_waiter(&waiter, false);
 	ret = rt_mutex_slowlock_locked(m, state, NULL, RT_MUTEX_MIN_CHAINWALK,
-				       &waiter);
+				       NULL, &waiter);
 	/*
 	 * The slowlock() above is guaranteed to return with the rtmutex (for
 	 * ret = 0) is now held, so there can't be a writer active. Increment
-- 
2.44.0