447 lines
12 KiB
Diff
447 lines
12 KiB
Diff
From: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
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Date: Mon, 28 Oct 2013 09:36:37 +0100
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Subject: rtmutex: Add RT aware ww locks
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.11/older/patches-4.11.9-rt7.tar.xz
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lockdep says:
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| --------------------------------------------------------------------------
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| | Wound/wait tests |
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| ---------------------
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| ww api failures: ok | ok | ok |
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| ww contexts mixing: ok | ok |
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| finishing ww context: ok | ok | ok | ok |
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| locking mismatches: ok | ok | ok |
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| EDEADLK handling: ok | ok | ok | ok | ok | ok | ok | ok | ok | ok |
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| spinlock nest unlocked: ok |
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| -----------------------------------------------------
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| |block | try |context|
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| -----------------------------------------------------
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| context: ok | ok | ok |
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| try: ok | ok | ok |
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| block: ok | ok | ok |
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| spinlock: ok | ok | ok |
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Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
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---
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kernel/locking/rtmutex.c | 273 ++++++++++++++++++++++++++++++++++++++++++-----
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1 file changed, 247 insertions(+), 26 deletions(-)
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--- a/kernel/locking/rtmutex.c
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+++ b/kernel/locking/rtmutex.c
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@@ -23,6 +23,7 @@
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#include <linux/sched/wake_q.h>
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#include <linux/sched/debug.h>
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#include <linux/timer.h>
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+#include <linux/ww_mutex.h>
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#include "rtmutex_common.h"
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@@ -1285,8 +1286,8 @@ int atomic_dec_and_spin_lock(atomic_t *a
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}
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EXPORT_SYMBOL(atomic_dec_and_spin_lock);
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- void
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-__rt_spin_lock_init(spinlock_t *lock, char *name, struct lock_class_key *key)
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+void
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+__rt_spin_lock_init(spinlock_t *lock, const char *name, struct lock_class_key *key)
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{
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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/*
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@@ -1300,6 +1301,40 @@ EXPORT_SYMBOL(__rt_spin_lock_init);
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#endif /* PREEMPT_RT_FULL */
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ static inline int __sched
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+__mutex_lock_check_stamp(struct rt_mutex *lock, struct ww_acquire_ctx *ctx)
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+{
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+ struct ww_mutex *ww = container_of(lock, struct ww_mutex, base.lock);
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+ struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx);
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+
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+ if (!hold_ctx)
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+ return 0;
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+
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+ if (unlikely(ctx == hold_ctx))
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+ return -EALREADY;
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+
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+ if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
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+ (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
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+#ifdef CONFIG_DEBUG_MUTEXES
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+ DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
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+ ctx->contending_lock = ww;
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+#endif
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+ return -EDEADLK;
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+ }
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+
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+ return 0;
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+}
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+#else
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+ static inline int __sched
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+__mutex_lock_check_stamp(struct rt_mutex *lock, struct ww_acquire_ctx *ctx)
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+{
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+ BUG();
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+ return 0;
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+}
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+
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+#endif
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+
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static inline int
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try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
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struct rt_mutex_waiter *waiter)
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@@ -1580,7 +1615,8 @@ void rt_mutex_init_waiter(struct rt_mute
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static int __sched
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__rt_mutex_slowlock(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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- struct rt_mutex_waiter *waiter)
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+ struct rt_mutex_waiter *waiter,
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+ struct ww_acquire_ctx *ww_ctx)
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{
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int ret = 0;
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@@ -1598,6 +1634,12 @@ static int __sched
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break;
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}
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+ if (ww_ctx && ww_ctx->acquired > 0) {
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+ ret = __mutex_lock_check_stamp(lock, ww_ctx);
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+ if (ret)
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+ break;
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+ }
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+
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raw_spin_unlock_irq(&lock->wait_lock);
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debug_rt_mutex_print_deadlock(waiter);
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@@ -1632,13 +1674,91 @@ static void rt_mutex_handle_deadlock(int
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}
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}
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+static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
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+ struct ww_acquire_ctx *ww_ctx)
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+{
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+#ifdef CONFIG_DEBUG_MUTEXES
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+ /*
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+ * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
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+ * but released with a normal mutex_unlock in this call.
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+ *
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+ * This should never happen, always use ww_mutex_unlock.
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+ */
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+ DEBUG_LOCKS_WARN_ON(ww->ctx);
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+
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+ /*
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+ * Not quite done after calling ww_acquire_done() ?
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+ */
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+ DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
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+
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+ if (ww_ctx->contending_lock) {
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+ /*
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+ * After -EDEADLK you tried to
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+ * acquire a different ww_mutex? Bad!
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+ */
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+ DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
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+
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+ /*
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+ * You called ww_mutex_lock after receiving -EDEADLK,
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+ * but 'forgot' to unlock everything else first?
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+ */
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+ DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
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+ ww_ctx->contending_lock = NULL;
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+ }
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+
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+ /*
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+ * Naughty, using a different class will lead to undefined behavior!
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+ */
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+ DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
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+#endif
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+ ww_ctx->acquired++;
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+}
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+
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+static void ww_mutex_account_lock(struct rt_mutex *lock,
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+ struct ww_acquire_ctx *ww_ctx)
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+{
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+ struct ww_mutex *ww = container_of(lock, struct ww_mutex, base.lock);
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+ struct rt_mutex_waiter *waiter, *n;
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+
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+ /*
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+ * This branch gets optimized out for the common case,
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+ * and is only important for ww_mutex_lock.
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+ */
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+ ww_mutex_lock_acquired(ww, ww_ctx);
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+ ww->ctx = ww_ctx;
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+
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+ /*
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+ * Give any possible sleeping processes the chance to wake up,
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+ * so they can recheck if they have to back off.
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+ */
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+ rbtree_postorder_for_each_entry_safe(waiter, n, &lock->waiters,
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+ tree_entry) {
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+ /* XXX debug rt mutex waiter wakeup */
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+
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+ BUG_ON(waiter->lock != lock);
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+ rt_mutex_wake_waiter(waiter);
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+ }
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+
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+}
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+
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+#else
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+
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+static void ww_mutex_account_lock(struct rt_mutex *lock,
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+ struct ww_acquire_ctx *ww_ctx)
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+{
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+ BUG();
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+}
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+#endif
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+
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/*
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* Slow path lock function:
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*/
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static int __sched
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rt_mutex_slowlock(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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- enum rtmutex_chainwalk chwalk)
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+ enum rtmutex_chainwalk chwalk,
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+ struct ww_acquire_ctx *ww_ctx)
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{
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struct rt_mutex_waiter waiter;
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unsigned long flags;
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@@ -1656,8 +1776,20 @@ rt_mutex_slowlock(struct rt_mutex *lock,
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*/
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raw_spin_lock_irqsave(&lock->wait_lock, flags);
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ if (ww_ctx) {
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+ struct ww_mutex *ww;
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+
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+ ww = container_of(lock, struct ww_mutex, base.lock);
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+ if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
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+ return -EALREADY;
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+ }
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+#endif
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+
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/* Try to acquire the lock again: */
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if (try_to_take_rt_mutex(lock, current, NULL)) {
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+ if (ww_ctx)
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+ ww_mutex_account_lock(lock, ww_ctx);
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raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
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return 0;
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}
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@@ -1672,13 +1804,23 @@ rt_mutex_slowlock(struct rt_mutex *lock,
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if (likely(!ret))
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/* sleep on the mutex */
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- ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
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+ ret = __rt_mutex_slowlock(lock, state, timeout, &waiter,
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+ ww_ctx);
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+ else if (ww_ctx) {
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+ /* ww_mutex received EDEADLK, let it become EALREADY */
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+ ret = __mutex_lock_check_stamp(lock, ww_ctx);
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+ BUG_ON(!ret);
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+ }
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if (unlikely(ret)) {
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__set_current_state(TASK_RUNNING);
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if (rt_mutex_has_waiters(lock))
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remove_waiter(lock, &waiter);
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- rt_mutex_handle_deadlock(ret, chwalk, &waiter);
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+ /* ww_mutex want to report EDEADLK/EALREADY, let them */
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+ if (!ww_ctx)
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+ rt_mutex_handle_deadlock(ret, chwalk, &waiter);
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+ } else if (ww_ctx) {
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+ ww_mutex_account_lock(lock, ww_ctx);
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}
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/*
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@@ -1808,29 +1950,33 @@ static bool __sched rt_mutex_slowunlock(
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*/
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static inline int
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rt_mutex_fastlock(struct rt_mutex *lock, int state,
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+ struct ww_acquire_ctx *ww_ctx,
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int (*slowfn)(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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- enum rtmutex_chainwalk chwalk))
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+ enum rtmutex_chainwalk chwalk,
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+ struct ww_acquire_ctx *ww_ctx))
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{
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if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
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return 0;
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- return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
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+ return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK, ww_ctx);
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}
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static inline int
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rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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enum rtmutex_chainwalk chwalk,
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+ struct ww_acquire_ctx *ww_ctx,
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int (*slowfn)(struct rt_mutex *lock, int state,
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struct hrtimer_sleeper *timeout,
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- enum rtmutex_chainwalk chwalk))
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+ enum rtmutex_chainwalk chwalk,
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+ struct ww_acquire_ctx *ww_ctx))
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{
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if (chwalk == RT_MUTEX_MIN_CHAINWALK &&
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likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
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return 0;
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- return slowfn(lock, state, timeout, chwalk);
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+ return slowfn(lock, state, timeout, chwalk, ww_ctx);
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}
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static inline int
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@@ -1881,7 +2027,7 @@ void __sched rt_mutex_lock(struct rt_mut
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{
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might_sleep();
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- rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock);
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+ rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, NULL, rt_mutex_slowlock);
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}
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EXPORT_SYMBOL_GPL(rt_mutex_lock);
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@@ -1898,7 +2044,7 @@ int __sched rt_mutex_lock_interruptible(
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{
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might_sleep();
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- return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock);
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+ return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, NULL, rt_mutex_slowlock);
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}
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EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
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@@ -1925,7 +2071,7 @@ int __sched rt_mutex_lock_killable(struc
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{
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might_sleep();
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- return rt_mutex_fastlock(lock, TASK_KILLABLE, rt_mutex_slowlock);
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+ return rt_mutex_fastlock(lock, TASK_KILLABLE, NULL, rt_mutex_slowlock);
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}
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EXPORT_SYMBOL_GPL(rt_mutex_lock_killable);
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@@ -1949,6 +2095,7 @@ rt_mutex_timed_lock(struct rt_mutex *loc
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return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
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RT_MUTEX_MIN_CHAINWALK,
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+ NULL,
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rt_mutex_slowlock);
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}
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EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
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@@ -2247,7 +2394,7 @@ int rt_mutex_wait_proxy_lock(struct rt_m
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raw_spin_lock_irq(&lock->wait_lock);
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/* sleep on the mutex */
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set_current_state(TASK_INTERRUPTIBLE);
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- ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
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+ ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter, NULL);
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/*
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* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
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* have to fix that up.
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@@ -2314,24 +2461,98 @@ bool rt_mutex_cleanup_proxy_lock(struct
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return cleanup;
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}
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+static inline int
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+ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
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+{
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+#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
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+ unsigned tmp;
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+
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+ if (ctx->deadlock_inject_countdown-- == 0) {
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+ tmp = ctx->deadlock_inject_interval;
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+ if (tmp > UINT_MAX/4)
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+ tmp = UINT_MAX;
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+ else
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+ tmp = tmp*2 + tmp + tmp/2;
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+
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+ ctx->deadlock_inject_interval = tmp;
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+ ctx->deadlock_inject_countdown = tmp;
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+ ctx->contending_lock = lock;
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+
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+ ww_mutex_unlock(lock);
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+
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+ return -EDEADLK;
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+ }
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+#endif
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+
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+ return 0;
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+}
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+
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#ifdef CONFIG_PREEMPT_RT_FULL
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-struct ww_mutex {
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-};
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-struct ww_acquire_ctx {
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-};
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-int __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx)
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+int __sched
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+ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
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{
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- BUG();
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+ int ret;
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+
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+ might_sleep();
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+
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+ mutex_acquire_nest(&lock->base.dep_map, 0, 0,
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+ ctx ? &ctx->dep_map : NULL, _RET_IP_);
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+ ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL, 0,
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+ ctx);
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+ if (ret)
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+ mutex_release(&lock->base.dep_map, 1, _RET_IP_);
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+ else if (!ret && ctx && ctx->acquired > 1)
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+ return ww_mutex_deadlock_injection(lock, ctx);
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+
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+ return ret;
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}
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-EXPORT_SYMBOL_GPL(__ww_mutex_lock);
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-int __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx)
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+EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible);
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+
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+int __sched
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+ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
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{
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- BUG();
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+ int ret;
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+
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+ might_sleep();
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+
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+ mutex_acquire_nest(&lock->base.dep_map, 0, 0,
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+ ctx ? &ctx->dep_map : NULL, _RET_IP_);
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+ ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL, 0,
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+ ctx);
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+ if (ret)
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+ mutex_release(&lock->base.dep_map, 1, _RET_IP_);
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+ else if (!ret && ctx && ctx->acquired > 1)
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+ return ww_mutex_deadlock_injection(lock, ctx);
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+
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+ return ret;
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}
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-EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);
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+EXPORT_SYMBOL_GPL(ww_mutex_lock);
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+
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void __sched ww_mutex_unlock(struct ww_mutex *lock)
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{
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- BUG();
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+ int nest = !!lock->ctx;
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+
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+ /*
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+ * The unlocking fastpath is the 0->1 transition from 'locked'
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+ * into 'unlocked' state:
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+ */
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+ if (nest) {
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+#ifdef CONFIG_DEBUG_MUTEXES
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+ DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
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+#endif
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+ if (lock->ctx->acquired > 0)
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+ lock->ctx->acquired--;
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+ lock->ctx = NULL;
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+ }
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+
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+ mutex_release(&lock->base.dep_map, nest, _RET_IP_);
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+ rt_mutex_unlock(&lock->base.lock);
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+}
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+EXPORT_SYMBOL(ww_mutex_unlock);
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+
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+int __rt_mutex_owner_current(struct rt_mutex *lock)
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+{
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+ return rt_mutex_owner(lock) == current;
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}
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-EXPORT_SYMBOL_GPL(ww_mutex_unlock);
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+EXPORT_SYMBOL(__rt_mutex_owner_current);
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#endif
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