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Date: Sun, 01 Apr 2018 21:42:03 +0100
From: David Howells <dhowells@...hat.com>
To: linux-kernel@...r.kernel.org
Subject: [PATCH 18/45] C++: Turn RCU accessors into inline template functions
Simplify the RCU accessor functions by turning them into inline template
functions. There's then no need for the use of casts built around typeof.
Signed-off-by: David Howells <dhowells@...hat.com>
---
include/linux/rcupdate.h | 124 +++++++++++++++++++++++++++++-----------------
1 file changed, 78 insertions(+), 46 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 043d04784675..328b312f09f0 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -1,4 +1,4 @@
-/*
+/* -*- c++ -*-
* Read-Copy Update mechanism for mutual exclusion
*
* This program is free software; you can redistribute it and/or modify
@@ -337,32 +337,50 @@ static inline void rcu_preempt_sleep_check(void) { }
#define rcu_dereference_sparse(p, space)
#endif /* #else #ifdef __CHECKER__ */
-#define __rcu_access_pointer(p, space) \
-({ \
- typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \
- rcu_dereference_sparse(p, space); \
- ((typeof(*p) __force __kernel *)(_________p1)); \
-})
-#define __rcu_dereference_check(p, c, space) \
-({ \
- /* Dependency order vs. p above. */ \
- typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \
- RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \
- rcu_dereference_sparse(p, space); \
- ((typeof(*p) __force __kernel *)(________p1)); \
-})
-#define __rcu_dereference_protected(p, c, space) \
-({ \
- RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \
- rcu_dereference_sparse(p, space); \
- ((typeof(*p) __force __kernel *)(p)); \
-})
-#define rcu_dereference_raw(p) \
-({ \
- /* Dependency order vs. p above. */ \
- typeof(p) ________p1 = READ_ONCE(p); \
- ((typeof(*p) __force __kernel *)(________p1)); \
-})
+template <typename T>
+T *__rcu_access_pointer(T *&p)
+{
+ /* Dependency order vs. p above. */
+ T *p1 = (T *__force)READ_ONCE(p);
+ rcu_dereference_sparse(p, __rcu);
+ return (T __force __kernel *)p1;
+}
+
+template <typename T>
+T *__rcu_dereference_check(T *&p, bool c)
+{
+ /* Dependency order vs. p above. */
+ T *p1 = (T *__force)READ_ONCE(p);
+ RCU_LOCKDEP_WARN(!c, "suspicious rcu_dereference_check() usage");
+ rcu_dereference_sparse(p, __rcu);
+ return (T __force __kernel *)p1;
+}
+
+template <typename T>
+T *__rcu_dereference_check(T *const &p, bool c)
+{
+ /* Dependency order vs. p above. */
+ T *p1 = (T *__force)READ_ONCE(p);
+ RCU_LOCKDEP_WARN(!c, "suspicious rcu_dereference_check() usage");
+ rcu_dereference_sparse(p, __rcu);
+ return (T __force __kernel *)p1;
+}
+
+template <typename T>
+T *__rcu_dereference_protected(T *&p, bool c)
+{
+ RCU_LOCKDEP_WARN(!c, "suspicious rcu_dereference_protected() usage");
+ rcu_dereference_sparse(p, __rcu);
+ return (T __force __kernel *)p;
+}
+
+template <typename T>
+T *rcu_dereference_raw(T *&p)
+{
+ /* Dependency order vs. p above. */
+ T *p1 = READ_ONCE(p);
+ return (T __force __kernel *)p1;
+}
/**
* RCU_INITIALIZER() - statically initialize an RCU-protected global variable
@@ -401,16 +419,14 @@ static inline void rcu_preempt_sleep_check(void) { }
* please be careful when making changes to rcu_assign_pointer() and the
* other macros that it invokes.
*/
-#define rcu_assign_pointer(p, v) \
-({ \
- uintptr_t _r_a_p__v = (uintptr_t)(v); \
- \
- if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL) \
- WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \
- else \
- smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
- _r_a_p__v; \
-})
+template <typename T>
+static inline void rcu_assign_pointer(T *&p, T *v)
+{
+ if (__builtin_constant_p(v) && !v)
+ WRITE_ONCE((p), v);
+ else
+ smp_store_release(&p, (T __force __rcu *)v);
+}
/**
* rcu_swap_protected() - swap an RCU and a regular pointer
@@ -482,8 +498,17 @@ static inline void rcu_preempt_sleep_check(void) { }
* which pointers are protected by RCU and checks that the pointer is
* annotated as __rcu.
*/
-#define rcu_dereference_check(p, c) \
- __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu)
+template <typename T>
+T *rcu_dereference_check(T *&p, bool c)
+{
+ return __rcu_dereference_check(p, c || rcu_read_lock_held());
+}
+
+template <typename T>
+T *rcu_dereference_check(T *const &p, bool c)
+{
+ return __rcu_dereference_check(p, c || rcu_read_lock_held());
+}
/**
* rcu_dereference_bh_check() - rcu_dereference_bh with debug checking
@@ -493,7 +518,7 @@ static inline void rcu_preempt_sleep_check(void) { }
* This is the RCU-bh counterpart to rcu_dereference_check().
*/
#define rcu_dereference_bh_check(p, c) \
- __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu)
+ __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held())
/**
* rcu_dereference_sched_check() - rcu_dereference_sched with debug checking
@@ -532,7 +557,7 @@ static inline void rcu_preempt_sleep_check(void) { }
* but very ugly failures.
*/
#define rcu_dereference_protected(p, c) \
- __rcu_dereference_protected((p), (c), __rcu)
+ __rcu_dereference_protected((p), (c))
/**
@@ -814,11 +839,18 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
* Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no
* ordering guarantees for either the CPU or the compiler.
*/
-#define RCU_INIT_POINTER(p, v) \
- do { \
- rcu_dereference_sparse(p, __rcu); \
- WRITE_ONCE(p, RCU_INITIALIZER(v)); \
- } while (0)
+template <typename T>
+static inline void RCU_INIT_POINTER(T *&p, T *v)
+{
+ rcu_dereference_sparse(p, __rcu);
+ WRITE_ONCE(p, (T __force __rcu *)v);
+}
+
+template <typename T>
+static inline void RCU_INIT_POINTER(T *&p, nullptr_t v)
+{
+ WRITE_ONCE(p, (T __force __rcu *)v);
+}
/**
* RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer
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