Re: [PATCH v2 2/7] x86: use long long for 64-bit atomic ops

[Dmitry Vyukov]

On Sun, May 28, 2017 at 1:02 AM,  <hpa@xxxxxxxxx> wrote:
> On May 26, 2017 12:09:04 PM PDT, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>>Some 64-bit atomic operations use 'long long' as operand/return type
>>(e.g. asm-generic/atomic64.h, arch/x86/include/asm/atomic64_32.h);
>>while others use 'long' (e.g. arch/x86/include/asm/atomic64_64.h).
>>This makes it impossible to write portable code.
>>For example, there is no format specifier that prints result of
>>atomic64_read() without warnings. atomic64_try_cmpxchg() is almost
>>impossible to use in portable fashion because it requires either
>>'long *' or 'long long *' as argument depending on arch.
>>
>>Switch arch/x86/include/asm/atomic64_64.h to 'long long'.
>>
>>Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
>>Cc: Mark Rutland <mark.rutland@xxxxxxx>
>>Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>>Cc: Will Deacon <will.deacon@xxxxxxx>
>>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
>>Cc: Ingo Molnar <mingo@xxxxxxxxxx>
>>Cc: kasan-dev@xxxxxxxxxxxxxxxx
>>Cc: linux-mm@xxxxxxxxx
>>Cc: linux-kernel@xxxxxxxxxxxxxxx
>>Cc: x86@xxxxxxxxxx
>>
>>---
>>Changes since v1:
>> - reverted stray s/long/long long/ replace in comment
>> - added arch/s390 changes to fix build errors/warnings
>>---
>> arch/s390/include/asm/atomic_ops.h | 14 +++++-----
>> arch/s390/include/asm/bitops.h     | 12 ++++-----
>>arch/x86/include/asm/atomic64_64.h | 52
>>+++++++++++++++++++-------------------
>> include/linux/types.h              |  2 +-
>> 4 files changed, 40 insertions(+), 40 deletions(-)
>>
>>diff --git a/arch/s390/include/asm/atomic_ops.h
>>b/arch/s390/include/asm/atomic_ops.h
>>index ac9e2b939d04..055a9083e52d 100644
>>--- a/arch/s390/include/asm/atomic_ops.h
>>+++ b/arch/s390/include/asm/atomic_ops.h
>>@@ -31,10 +31,10 @@ __ATOMIC_OPS(__atomic_and, int, "lan")
>> __ATOMIC_OPS(__atomic_or,  int, "lao")
>> __ATOMIC_OPS(__atomic_xor, int, "lax")
>>
>>-__ATOMIC_OPS(__atomic64_add, long, "laag")
>>-__ATOMIC_OPS(__atomic64_and, long, "lang")
>>-__ATOMIC_OPS(__atomic64_or,  long, "laog")
>>-__ATOMIC_OPS(__atomic64_xor, long, "laxg")
>>+__ATOMIC_OPS(__atomic64_add, long long, "laag")
>>+__ATOMIC_OPS(__atomic64_and, long long, "lang")
>>+__ATOMIC_OPS(__atomic64_or,  long long, "laog")
>>+__ATOMIC_OPS(__atomic64_xor, long long, "laxg")
>>
>> #undef __ATOMIC_OPS
>> #undef __ATOMIC_OP
>>@@ -46,7 +46,7 @@ static inline void __atomic_add_const(int val, int
>>*ptr)
>>               : [ptr] "+Q" (*ptr) : [val] "i" (val) : "cc");
>> }
>>
>>-static inline void __atomic64_add_const(long val, long *ptr)
>>+static inline void __atomic64_add_const(long val, long long *ptr)
>> {
>>       asm volatile(
>>               "       agsi    %[ptr],%[val]\n"
>>@@ -82,7 +82,7 @@ __ATOMIC_OPS(__atomic_xor, "xr")
>> #undef __ATOMIC_OPS
>>
>> #define __ATOMIC64_OP(op_name, op_string)                             \
>>-static inline long op_name(long val, long *ptr)                               \
>>+static inline long op_name(long val, long long *ptr)                  \
>> {                                                                     \
>>       long old, new;                                                  \
>>                                                                       \
>>@@ -118,7 +118,7 @@ static inline int __atomic_cmpxchg(int *ptr, int
>>old, int new)
>>       return old;
>> }
>>
>>-static inline long __atomic64_cmpxchg(long *ptr, long old, long new)
>>+static inline long __atomic64_cmpxchg(long long *ptr, long old, long
>>new)
>> {
>>       asm volatile(
>>               "       csg     %[old],%[new],%[ptr]"
>>diff --git a/arch/s390/include/asm/bitops.h
>>b/arch/s390/include/asm/bitops.h
>>index d92047da5ccb..8912f52bca5d 100644
>>--- a/arch/s390/include/asm/bitops.h
>>+++ b/arch/s390/include/asm/bitops.h
>>@@ -80,7 +80,7 @@ static inline void set_bit(unsigned long nr, volatile
>>unsigned long *ptr)
>>       }
>> #endif
>>       mask = 1UL << (nr & (BITS_PER_LONG - 1));
>>-      __atomic64_or(mask, addr);
>>+      __atomic64_or(mask, (long long *)addr);
>> }
>>
>>static inline void clear_bit(unsigned long nr, volatile unsigned long
>>*ptr)
>>@@ -101,7 +101,7 @@ static inline void clear_bit(unsigned long nr,
>>volatile unsigned long *ptr)
>>       }
>> #endif
>>       mask = ~(1UL << (nr & (BITS_PER_LONG - 1)));
>>-      __atomic64_and(mask, addr);
>>+      __atomic64_and(mask, (long long *)addr);
>> }
>>
>>static inline void change_bit(unsigned long nr, volatile unsigned long
>>*ptr)
>>@@ -122,7 +122,7 @@ static inline void change_bit(unsigned long nr,
>>volatile unsigned long *ptr)
>>       }
>> #endif
>>       mask = 1UL << (nr & (BITS_PER_LONG - 1));
>>-      __atomic64_xor(mask, addr);
>>+      __atomic64_xor(mask, (long long *)addr);
>> }
>>
>> static inline int
>>@@ -132,7 +132,7 @@ test_and_set_bit(unsigned long nr, volatile
>>unsigned long *ptr)
>>       unsigned long old, mask;
>>
>>       mask = 1UL << (nr & (BITS_PER_LONG - 1));
>>-      old = __atomic64_or_barrier(mask, addr);
>>+      old = __atomic64_or_barrier(mask, (long long *)addr);
>>       return (old & mask) != 0;
>> }
>>
>>@@ -143,7 +143,7 @@ test_and_clear_bit(unsigned long nr, volatile
>>unsigned long *ptr)
>>       unsigned long old, mask;
>>
>>       mask = ~(1UL << (nr & (BITS_PER_LONG - 1)));
>>-      old = __atomic64_and_barrier(mask, addr);
>>+      old = __atomic64_and_barrier(mask, (long long *)addr);
>>       return (old & ~mask) != 0;
>> }
>>
>>@@ -154,7 +154,7 @@ test_and_change_bit(unsigned long nr, volatile
>>unsigned long *ptr)
>>       unsigned long old, mask;
>>
>>       mask = 1UL << (nr & (BITS_PER_LONG - 1));
>>-      old = __atomic64_xor_barrier(mask, addr);
>>+      old = __atomic64_xor_barrier(mask, (long long *)addr);
>>       return (old & mask) != 0;
>> }
>>
>>diff --git a/arch/x86/include/asm/atomic64_64.h
>>b/arch/x86/include/asm/atomic64_64.h
>>index 8db8879a6d8c..8555cd19a916 100644
>>--- a/arch/x86/include/asm/atomic64_64.h
>>+++ b/arch/x86/include/asm/atomic64_64.h
>>@@ -16,7 +16,7 @@
>>  * Atomically reads the value of @v.
>>  * Doesn't imply a read memory barrier.
>>  */
>>-static inline long atomic64_read(const atomic64_t *v)
>>+static inline long long atomic64_read(const atomic64_t *v)
>> {
>>       return READ_ONCE((v)->counter);
>> }
>>@@ -28,7 +28,7 @@ static inline long atomic64_read(const atomic64_t *v)
>>  *
>>  * Atomically sets the value of @v to @i.
>>  */
>>-static inline void atomic64_set(atomic64_t *v, long i)
>>+static inline void atomic64_set(atomic64_t *v, long long i)
>> {
>>       WRITE_ONCE(v->counter, i);
>> }
>>@@ -40,7 +40,7 @@ static inline void atomic64_set(atomic64_t *v, long
>>i)
>>  *
>>  * Atomically adds @i to @v.
>>  */
>>-static __always_inline void atomic64_add(long i, atomic64_t *v)
>>+static __always_inline void atomic64_add(long long i, atomic64_t *v)
>> {
>>       asm volatile(LOCK_PREFIX "addq %1,%0"
>>                    : "=m" (v->counter)
>>@@ -54,7 +54,7 @@ static __always_inline void atomic64_add(long i,
>>atomic64_t *v)
>>  *
>>  * Atomically subtracts @i from @v.
>>  */
>>-static inline void atomic64_sub(long i, atomic64_t *v)
>>+static inline void atomic64_sub(long long i, atomic64_t *v)
>> {
>>       asm volatile(LOCK_PREFIX "subq %1,%0"
>>                    : "=m" (v->counter)
>>@@ -70,7 +70,7 @@ static inline void atomic64_sub(long i, atomic64_t
>>*v)
>>  * true if the result is zero, or false for all
>>  * other cases.
>>  */
>>-static inline bool atomic64_sub_and_test(long i, atomic64_t *v)
>>+static inline bool atomic64_sub_and_test(long long i, atomic64_t *v)
>> {
>>       GEN_BINARY_RMWcc(LOCK_PREFIX "subq", v->counter, "er", i, "%0", e);
>> }
>>@@ -136,7 +136,7 @@ static inline bool atomic64_inc_and_test(atomic64_t
>>*v)
>>  * if the result is negative, or false when
>>  * result is greater than or equal to zero.
>>  */
>>-static inline bool atomic64_add_negative(long i, atomic64_t *v)
>>+static inline bool atomic64_add_negative(long long i, atomic64_t *v)
>> {
>>       GEN_BINARY_RMWcc(LOCK_PREFIX "addq", v->counter, "er", i, "%0", s);
>> }
>>@@ -148,22 +148,22 @@ static inline bool atomic64_add_negative(long i,
>>atomic64_t *v)
>>  *
>>  * Atomically adds @i to @v and returns @i + @v
>>  */
>>-static __always_inline long atomic64_add_return(long i, atomic64_t *v)
>>+static __always_inline long long atomic64_add_return(long long i,
>>atomic64_t *v)
>> {
>>       return i + xadd(&v->counter, i);
>> }
>>
>>-static inline long atomic64_sub_return(long i, atomic64_t *v)
>>+static inline long long atomic64_sub_return(long long i, atomic64_t
>>*v)
>> {
>>       return atomic64_add_return(-i, v);
>> }
>>
>>-static inline long atomic64_fetch_add(long i, atomic64_t *v)
>>+static inline long long atomic64_fetch_add(long long i, atomic64_t *v)
>> {
>>       return xadd(&v->counter, i);
>> }
>>
>>-static inline long atomic64_fetch_sub(long i, atomic64_t *v)
>>+static inline long long atomic64_fetch_sub(long long i, atomic64_t *v)
>> {
>>       return xadd(&v->counter, -i);
>> }
>>@@ -171,18 +171,18 @@ static inline long atomic64_fetch_sub(long i,
>>atomic64_t *v)
>> #define atomic64_inc_return(v)  (atomic64_add_return(1, (v)))
>> #define atomic64_dec_return(v)  (atomic64_sub_return(1, (v)))
>>
>>-static inline long atomic64_cmpxchg(atomic64_t *v, long old, long new)
>>+static inline long long atomic64_cmpxchg(atomic64_t *v, long long old,
>>long long new)
>> {
>>       return cmpxchg(&v->counter, old, new);
>> }
>>
>> #define atomic64_try_cmpxchg atomic64_try_cmpxchg
>>-static __always_inline bool atomic64_try_cmpxchg(atomic64_t *v, long
>>*old, long new)
>>+static __always_inline bool atomic64_try_cmpxchg(atomic64_t *v, long
>>long *old, long long new)
>> {
>>       return try_cmpxchg(&v->counter, old, new);
>> }
>>
>>-static inline long atomic64_xchg(atomic64_t *v, long new)
>>+static inline long long atomic64_xchg(atomic64_t *v, long long new)
>> {
>>       return xchg(&v->counter, new);
>> }
>>@@ -196,9 +196,9 @@ static inline long atomic64_xchg(atomic64_t *v,
>>long new)
>>  * Atomically adds @a to @v, so long as it was not @u.
>>  * Returns the old value of @v.
>>  */
>>-static inline bool atomic64_add_unless(atomic64_t *v, long a, long u)
>>+static inline bool atomic64_add_unless(atomic64_t *v, long long a,
>>long long u)
>> {
>>-      long c = atomic64_read(v);
>>+      long long c = atomic64_read(v);
>>       do {
>>               if (unlikely(c == u))
>>                       return false;
>>@@ -215,9 +215,9 @@ static inline bool atomic64_add_unless(atomic64_t
>>*v, long a, long u)
>>  * The function returns the old value of *v minus 1, even if
>>  * the atomic variable, v, was not decremented.
>>  */
>>-static inline long atomic64_dec_if_positive(atomic64_t *v)
>>+static inline long long atomic64_dec_if_positive(atomic64_t *v)
>> {
>>-      long dec, c = atomic64_read(v);
>>+      long long dec, c = atomic64_read(v);
>>       do {
>>               dec = c - 1;
>>               if (unlikely(dec < 0))
>>@@ -226,7 +226,7 @@ static inline long
>>atomic64_dec_if_positive(atomic64_t *v)
>>       return dec;
>> }
>>
>>-static inline void atomic64_and(long i, atomic64_t *v)
>>+static inline void atomic64_and(long long i, atomic64_t *v)
>> {
>>       asm volatile(LOCK_PREFIX "andq %1,%0"
>>                       : "+m" (v->counter)
>>@@ -234,16 +234,16 @@ static inline void atomic64_and(long i,
>>atomic64_t *v)
>>                       : "memory");
>> }
>>
>>-static inline long atomic64_fetch_and(long i, atomic64_t *v)
>>+static inline long long atomic64_fetch_and(long long i, atomic64_t *v)
>> {
>>-      long val = atomic64_read(v);
>>+      long long val = atomic64_read(v);
>>
>>       do {
>>       } while (!atomic64_try_cmpxchg(v, &val, val & i));
>>       return val;
>> }
>>
>>-static inline void atomic64_or(long i, atomic64_t *v)
>>+static inline void atomic64_or(long long i, atomic64_t *v)
>> {
>>       asm volatile(LOCK_PREFIX "orq %1,%0"
>>                       : "+m" (v->counter)
>>@@ -251,16 +251,16 @@ static inline void atomic64_or(long i, atomic64_t
>>*v)
>>                       : "memory");
>> }
>>
>>-static inline long atomic64_fetch_or(long i, atomic64_t *v)
>>+static inline long long atomic64_fetch_or(long long i, atomic64_t *v)
>> {
>>-      long val = atomic64_read(v);
>>+      long long val = atomic64_read(v);
>>
>>       do {
>>       } while (!atomic64_try_cmpxchg(v, &val, val | i));
>>       return val;
>> }
>>
>>-static inline void atomic64_xor(long i, atomic64_t *v)
>>+static inline void atomic64_xor(long long i, atomic64_t *v)
>> {
>>       asm volatile(LOCK_PREFIX "xorq %1,%0"
>>                       : "+m" (v->counter)
>>@@ -268,9 +268,9 @@ static inline void atomic64_xor(long i, atomic64_t
>>*v)
>>                       : "memory");
>> }
>>
>>-static inline long atomic64_fetch_xor(long i, atomic64_t *v)
>>+static inline long long atomic64_fetch_xor(long long i, atomic64_t *v)
>> {
>>-      long val = atomic64_read(v);
>>+      long long val = atomic64_read(v);
>>
>>       do {
>>       } while (!atomic64_try_cmpxchg(v, &val, val ^ i));
>>diff --git a/include/linux/types.h b/include/linux/types.h
>>index 1e7bd24848fc..569fc6db1bd5 100644
>>--- a/include/linux/types.h
>>+++ b/include/linux/types.h
>>@@ -177,7 +177,7 @@ typedef struct {
>>
>> #ifdef CONFIG_64BIT
>> typedef struct {
>>-      long counter;
>>+      long long counter;
>> } atomic64_t;
>> #endif
>>
>
> NAK - this is what u64/s64 is for.


Hi,

Patch 3 adds atomic-instrumented.h which now contains:

+static __always_inline long long atomic64_read(const atomic64_t *v)
+{
+       return arch_atomic64_read(v);
+}

without this patch that will become

+static __always_inline s64 atomic64_read(const atomic64_t *v)

Right?