To cover scenarios where the scope of the guard differs from the scope
of its activation, introduce DEFINE_INACTIVE_GUARD() and activate_guard().
Here is an example use for a conditionally activated guard variable:
void func(bool a)
{
DEFINE_INACTIVE_GUARD(preempt_notrace, myguard);
[...]
if (a) {
might_sleep();
activate_guard(preempt_notrace, myguard)();
}
[ protected code ]
}
Signed-off-by: Mathieu Desnoyers <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Greg KH <[email protected]>
Cc: Sean Christopherson <[email protected]>
---
include/linux/cleanup.h | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 1247e67a6161..5f031cce97ca 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -149,12 +149,20 @@ static inline class_##_name##_t
class_##_name##ext##_constructor(_init_args) \
* similar to scoped_guard(), except it does fail when the lock
* acquire fails.
*
+ * DEFINE_INACTIVE_GUARD(name, var):
+ * define an inactive guard variable in a given scope, initialized to
NULL.
+ *
+ * activate_guard(name, var)(args...):
+ * activate a guard variable with its constructor, if it is not already
+ * activated.
*/
#define DECLARE_GUARD(_name, _type, _lock, _unlock) \
DECLARE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }),
_type _T); \
static inline void * class_##_name##_lock_ptr(class_##_name##_t *_T) \
- { return *_T; }
+ { return *_T; } \
+ static inline class_##_name##_t class_##_name##_null(void) \
+ { return NULL; }
#define DECLARE_GUARD_COND(_name, _ext, _condlock) \
EXTEND_CLASS(_name, _ext, \
@@ -178,6 +186,14 @@ static inline class_##_name##_t
class_##_name##ext##_constructor(_init_args) \
if (!__guard_ptr(_name)(&scope)) _fail; \
else
+#define DEFINE_INACTIVE_GUARD(_name, _var) \
+ class_##_name##_t _var __cleanup(class_##_name##_destructor) = \
+ class_##_name##_null()
+
+#define activate_guard(_name, _var) \
+ if (!class_##_name##_lock_ptr(&(_var))) \
+ _var = class_##_name##_constructor
+
/*
* Additional helper macros for generating lock guards with types, either for
* locks that don't have a native type (eg. RCU, preempt) or those that need a
@@ -212,6 +228,11 @@ static inline void
class_##_name##_destructor(class_##_name##_t *_T) \
static inline void *class_##_name##_lock_ptr(class_##_name##_t *_T) \
{ \
return _T->lock; \
+} \
+static inline class_##_name##_t class_##_name##_null(void) \
+{ \
+ class_##_name##_t _t = { .lock = NULL }; \
+ return _t; \
}
--
2.39.2
