Since the smp_mb__{before,after}*() ops are fundamentally dependent on
how an arch can implement atomics it doesn't make sense to have 3
variants of them. They must all be the same.
Furthermore, the 3 variants suggest they're only valid for those 3
atomic ops, while we have many more where they could be applied.
So move away from
smp_mb__{before,after}_{atomic,clear}_{dec,inc,bit}() and reduce the
interface to just the two: smp_mb__{before,after}_atomic().
This patch prepares the way by introducing default implementations in
asm-generic/barrier.h that default to a full barrier and providing
__deprecated inlines for the previous 6 barriers if they're not
provided by the arch.
This should allow for a mostly painless transition (lots of deprecated
warns in the interim).
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
include/asm-generic/atomic.h | 7 +------
include/asm-generic/barrier.h | 8 ++++++++
include/asm-generic/bitops.h | 9 +--------
include/linux/atomic.h | 36 ++++++++++++++++++++++++++++++++++++
include/linux/bitops.h | 20 ++++++++++++++++++++
kernel/sched/core.c | 16 ++++++++++++++++
6 files changed, 82 insertions(+), 14 deletions(-)
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -16,6 +16,7 @@
#define __ASM_GENERIC_ATOMIC_H
#include <asm/cmpxchg.h>
+#include <asm/barrier.h>
#ifdef CONFIG_SMP
/* Force people to define core atomics */
@@ -182,11 +183,5 @@ static inline void atomic_set_mask(unsig
}
#endif
-/* Assume that atomic operations are already serializing */
-#define smp_mb__before_atomic_dec() barrier()
-#define smp_mb__after_atomic_dec() barrier()
-#define smp_mb__before_atomic_inc() barrier()
-#define smp_mb__after_atomic_inc() barrier()
-
#endif /* __KERNEL__ */
#endif /* __ASM_GENERIC_ATOMIC_H */
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -62,6 +62,14 @@
#define set_mb(var, value) do { (var) = (value); mb(); } while (0)
#endif
+#ifndef smp_mb__before_atomic
+#define smp_mb__before_atomic() smp_mb()
+#endif
+
+#ifndef smp_mb__after_atomic
+#define smp_mb__after_atomic() smp_mb()
+#endif
+
#define smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
--- a/include/asm-generic/bitops.h
+++ b/include/asm-generic/bitops.h
@@ -11,14 +11,7 @@
#include <linux/irqflags.h>
#include <linux/compiler.h>
-
-/*
- * clear_bit may not imply a memory barrier
- */
-#ifndef smp_mb__before_clear_bit
-#define smp_mb__before_clear_bit() smp_mb()
-#define smp_mb__after_clear_bit() smp_mb()
-#endif
+#include <asm/barrier.h>
#include <asm-generic/bitops/__ffs.h>
#include <asm-generic/bitops/ffz.h>
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -3,6 +3,42 @@
#define _LINUX_ATOMIC_H
#include <asm/atomic.h>
+/*
+ * Provide __deprecated wrappers for the new interface, avoid flag day changes.
+ * We need the ugly external functions to break header recursion hell.
+ */
+#ifndef smp_mb__before_atomic_inc
+static inline void __deprecated smp_mb__before_atomic_inc(void)
+{
+ extern void __smp_mb__before_atomic(void);
+ __smp_mb__before_atomic();
+}
+#endif
+
+#ifndef smp_mb__after_atomic_inc
+static inline void __deprecated smp_mb__after_atomic_inc(void)
+{
+ extern void __smp_mb__after_atomic(void);
+ __smp_mb__after_atomic();
+}
+#endif
+
+#ifndef smp_mb__before_atomic_dec
+static inline void __deprecated smp_mb__before_atomic_dec(void)
+{
+ extern void __smp_mb__before_atomic(void);
+ __smp_mb__before_atomic();
+}
+#endif
+
+#ifndef smp_mb__after_atomic_dec
+static inline void __deprecated smp_mb__after_atomic_dec(void)
+{
+ extern void __smp_mb__after_atomic(void);
+ __smp_mb__after_atomic();
+}
+#endif
+
/**
* atomic_add_unless - add unless the number is already a given value
* @v: pointer of type atomic_t
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -32,6 +32,26 @@ extern unsigned long __sw_hweight64(__u6
*/
#include <asm/bitops.h>
+/*
+ * Provide __deprecated wrappers for the new interface, avoid flag day changes.
+ * We need the ugly external functions to break header recursion hell.
+ */
+#ifndef smp_mb__before_clear_bit
+static inline void __deprecated smp_mb__before_clear_bit(void)
+{
+ extern void __smp_mb__before_atomic(void);
+ __smp_mb__before_atomic();
+}
+#endif
+
+#ifndef smp_mb__after_clear_bit
+static inline void __deprecated smp_mb__after_clear_bit(void)
+{
+ extern void __smp_mb__after_atomic(void);
+ __smp_mb__after_atomic();
+}
+#endif
+
#define for_each_set_bit(bit, addr, size) \
for ((bit) = find_first_bit((addr), (size)); \
(bit) < (size); \
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -89,6 +89,22 @@
#define CREATE_TRACE_POINTS
#include <trace/events/sched.h>
+#ifdef smp_mb__before_atomic
+void __smp_mb__before_atomic(void)
+{
+ smp_mb__before_atomic();
+}
+EXPORT_SYMBOL(__smp_mb__before_atomic);
+#endif
+
+#ifdef smp_mb__after_atomic
+void __smp_mb__after_atomic(void)
+{
+ smp_mb__after_atomic();
+}
+EXPORT_SYMBOL(__smp_mb__after_atomic);
+#endif
+
void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period)
{
unsigned long delta;
--
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