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Date: Sat, 27 May 2017 16:02:31 -0700
From: hpa@...or.com
To: Dmitry Vyukov <dvyukov@...gle.com>, mark.rutland@....com,
peterz@...radead.org, mingo@...hat.com, will.deacon@....com
CC: akpm@...ux-foundation.org, aryabinin@...tuozzo.com,
kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
x86@...nel.org, tglx@...utronix.de, willy@...radead.org,
linux-mm@...ck.org
Subject: Re: [PATCH v2 2/7] x86: use long long for 64-bit atomic ops
On May 26, 2017 12:09:04 PM PDT, Dmitry Vyukov <dvyukov@...gle.com> 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@...gle.com>
>Cc: Mark Rutland <mark.rutland@....com>
>Cc: Peter Zijlstra <peterz@...radead.org>
>Cc: Will Deacon <will.deacon@....com>
>Cc: Andrew Morton <akpm@...ux-foundation.org>
>Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
>Cc: Ingo Molnar <mingo@...hat.com>
>Cc: kasan-dev@...glegroups.com
>Cc: linux-mm@...ck.org
>Cc: linux-kernel@...r.kernel.org
>Cc: x86@...nel.org
>
>---
>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.
--
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