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-rw-r--r--include/linux/mutex.h8
-rw-r--r--kernel/mutex.c44
-rw-r--r--lib/Kconfig.debug13
3 files changed, 62 insertions, 3 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index a56b0ccc8a6..3793ed7feee 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -98,6 +98,10 @@ struct ww_acquire_ctx {
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
+#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
+ unsigned deadlock_inject_interval;
+ unsigned deadlock_inject_countdown;
+#endif
};
struct ww_mutex {
@@ -283,6 +287,10 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
&ww_class->acquire_key, 0);
mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_);
#endif
+#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
+ ctx->deadlock_inject_interval = 1;
+ ctx->deadlock_inject_countdown = ctx->stamp & 0xf;
+#endif
}
/**
diff --git a/kernel/mutex.c b/kernel/mutex.c
index fc801aafe8f..e581ada5faf 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -651,22 +651,60 @@ mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
+static inline int
+ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
+ unsigned 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;
+}
int __sched
__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
+ int ret;
+
might_sleep();
- return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
+ ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
0, &ctx->dep_map, _RET_IP_, ctx);
+ if (!ret && ctx->acquired > 0)
+ return ww_mutex_deadlock_injection(lock, ctx);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(__ww_mutex_lock);
int __sched
__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
+ int ret;
+
might_sleep();
- return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
- 0, &ctx->dep_map, _RET_IP_, ctx);
+ ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
+ 0, &ctx->dep_map, _RET_IP_, ctx);
+
+ if (!ret && ctx->acquired > 0)
+ return ww_mutex_deadlock_injection(lock, ctx);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 566cf2bc08e..7154f799541 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -547,6 +547,19 @@ config DEBUG_MUTEXES
This feature allows mutex semantics violations to be detected and
reported.
+config DEBUG_WW_MUTEX_SLOWPATH
+ bool "Wait/wound mutex debugging: Slowpath testing"
+ depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
+ select DEBUG_LOCK_ALLOC
+ select DEBUG_SPINLOCK
+ select DEBUG_MUTEXES
+ help
+ This feature enables slowpath testing for w/w mutex users by
+ injecting additional -EDEADLK wound/backoff cases. Together with
+ the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
+ will test all possible w/w mutex interface abuse with the
+ exception of simply not acquiring all the required locks.
+
config DEBUG_LOCK_ALLOC
bool "Lock debugging: detect incorrect freeing of live locks"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT