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

From: hpa
Date: Sun May 28 2017 - 05:47:03 EST

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In reply to: Dmitry Vyukov: "Re: [PATCH v2 2/7] x86: use long long for 64-bit atomic ops"
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On May 28, 2017 2:29:32 AM PDT, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>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?

Yes.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

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