[PATCH 09/10] fault injection: spin_trylock() fault injection

[Vegard Nossum <vegard.nossum@oracle.com>]

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
---
 include/linux/spinlock.h  | 12 ++++++++++++
 kernel/locking/spinlock.c | 19 +++++++++++++++++++
 lib/Kconfig.debug         |  6 ++++++
 3 files changed, 37 insertions(+)

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 47dd0ce..2fd1fee 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -307,8 +307,20 @@ static __always_inline void spin_lock_bh(spinlock_t *lock)
 	raw_spin_lock_bh(&lock->rlock);
 }
 
+#if defined(CONFIG_SMP) && defined(CONFIG_FAIL_SPINLOCK)
+extern bool should_fail_spinlock(spinlock_t *lock);
+#else
+static __always_inline bool should_fail_spinlock(spinlock_t *lock)
+{
+	return false;
+}
+#endif
+
 static __always_inline int spin_trylock(spinlock_t *lock)
 {
+	if (should_fail_spinlock(lock))
+		return 0;
+
 	return raw_spin_trylock(&lock->rlock);
 }
 
diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c
index db3ccb1..d57800f 100644
--- a/kernel/locking/spinlock.c
+++ b/kernel/locking/spinlock.c
@@ -14,6 +14,7 @@
  * frame contact the architecture maintainers.
  */
 
+#include <linux/fault-inject.h>
 #include <linux/linkage.h>
 #include <linux/preempt.h>
 #include <linux/spinlock.h>
@@ -405,3 +406,21 @@ notrace int in_lock_functions(unsigned long addr)
 	&& addr < (unsigned long)__lock_text_end;
 }
 EXPORT_SYMBOL(in_lock_functions);
+
+#ifdef CONFIG_FAIL_SPINLOCK
+static DECLARE_FAULT_ATTR(fail_spinlock);
+
+static int __init fail_spinlock_debugfs(void)
+{
+	struct dentry *dir = fault_create_debugfs_attr("fail_spinlock",
+		NULL, &fail_spinlock);
+	return PTR_ERR_OR_ZERO(dir);
+}
+late_initcall(fail_spinlock_debugfs);
+
+bool should_fail_spinlock(spinlock_t *lock)
+{
+	return should_fail(&fail_spinlock, 1);
+}
+
+#endif
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 342f0a1f..1f13d02 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1681,6 +1681,12 @@ config FAIL_RW_SEMAPHORE
 	help
 	  Provide fault-injection capability for down_{read,write}_trylock().
 
+config FAIL_SPINLOCK
+	bool "Fault-injection capability for spinlocks"
+	depends on FAULT_INJECTION
+	help
+	  Provide fault-injection capability for spin_trylock().
+
 config FAULT_INJECTION_DEBUG_FS
 	bool "Debugfs entries for fault-injection capabilities"
 	depends on FAULT_INJECTION && SYSFS && DEBUG_FS
-- 
2.10.0.479.g221bd91