[PATCH 05/10] fault injection: mutex_trylock() fault injection

[Vegard Nossum]

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
---
 kernel/locking/mutex.c | 32 ++++++++++++++++++++++++++++++++
 lib/Kconfig.debug      |  6 ++++++
 2 files changed, 38 insertions(+)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index a70b90d..0651ca6 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -17,6 +17,7 @@
  *
  * Also see Documentation/locking/mutex-design.txt.
  */
+#include <linux/fault-inject.h>
 #include <linux/mutex.h>
 #include <linux/ww_mutex.h>
 #include <linux/sched.h>
@@ -887,6 +888,34 @@ static inline int __mutex_trylock_slowpath(atomic_t *lock_count)
 	return prev == 1;
 }
 
+#ifdef CONFIG_FAIL_MUTEX
+DECLARE_FAULT_ATTR(fail_mutex);
+
+static int __init setup_fail_mutex(char *str)
+{
+	return setup_fault_attr(&fail_mutex, str);
+}
+__setup("fail_mutex=", setup_fail_mutex);
+
+static int __init fail_mutex_debugfs(void)
+{
+	struct dentry *dir = fault_create_debugfs_attr("fail_mutex",
+		NULL, &fail_mutex);
+	return PTR_ERR_OR_ZERO(dir);
+}
+late_initcall(fail_mutex_debugfs);
+
+static inline bool should_fail_mutex(struct mutex *lock)
+{
+	return should_fail(&fail_mutex, 1);
+}
+#else
+static inline bool should_fail_mutex(struct mutex *lock)
+{
+	return false;
+}
+#endif
+
 /**
  * mutex_trylock - try to acquire the mutex, without waiting
  * @lock: the mutex to be acquired
@@ -905,6 +934,9 @@ int __sched mutex_trylock(struct mutex *lock)
 {
 	int ret;
 
+	if (should_fail_mutex(lock))
+		return 0;
+
 	ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath);
 	if (ret)
 		mutex_set_owner(lock);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5896b6f..0043e66 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1657,6 +1657,12 @@ config FAIL_FUTEX
 	help
 	  Provide fault-injection capability for futexes.
 
+config FAIL_MUTEX
+	bool "Fault-injection capability for mutexes"
+	depends on FAULT_INJECTION
+	help
+	  Provide fault-injection capability for mutex_trylock().
+
 config FAULT_INJECTION_DEBUG_FS
 	bool "Debugfs entries for fault-injection capabilities"
 	depends on FAULT_INJECTION && SYSFS && DEBUG_FS
-- 
1.9.1