From: Boqun Feng <boqun.feng@gmail.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-kernel@vger.kernel.org, ardb@kernel.org, arnd@arndb.de,
peterz@infradead.org, will@kernel.org
Subject: Re: [PATCH v2] atomics: fix atomic64_{read_acquire,set_release} fallbacks
Date: Fri, 4 Feb 2022 08:20:25 +0800 [thread overview]
Message-ID: <YfxxSX3v6nSJ0tKo@tardis> (raw)
In-Reply-To: <20220203161243.3955547-1-mark.rutland@arm.com>
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On Thu, Feb 03, 2022 at 04:12:43PM +0000, Mark Rutland wrote:
> diff --git a/include/linux/atomic/atomic-arch-fallback.h b/include/linux/atomic/atomic-arch-fallback.h
> index a3dba31df01e..6db58d180866 100644
> --- a/include/linux/atomic/atomic-arch-fallback.h
> +++ b/include/linux/atomic/atomic-arch-fallback.h
> @@ -151,7 +151,16 @@
> static __always_inline int
> arch_atomic_read_acquire(const atomic_t *v)
> {
> - return smp_load_acquire(&(v)->counter);
> + int ret;
> +
> + if (__native_word(atomic_t)) {
> + ret = smp_load_acquire(&(v)->counter);
> + } else {
> + ret = arch_atomic_read(v);
> + __atomic_acquire_fence();
> + }
> +
> + return ret;
> }
> #define arch_atomic_read_acquire arch_atomic_read_acquire
> #endif
> @@ -160,7 +169,12 @@ arch_atomic_read_acquire(const atomic_t *v)
> static __always_inline void
> arch_atomic_set_release(atomic_t *v, int i)
> {
> - smp_store_release(&(v)->counter, i);
> + if (__native_word(atomic_t)) {
> + smp_store_release(&(v)->counter, i);
> + } else {
> + __atomic_release_fence();
> + arch_atomic_set(v, i);
> + }
> }
The changes for atomic_t are not necessary, right? They are correct but
"side effects" because of the change in scripts. If so, it's better to
mention this somewhere.
Regards,
Boqun
> #define arch_atomic_set_release arch_atomic_set_release
> #endif
> @@ -1258,7 +1272,16 @@ arch_atomic_dec_if_positive(atomic_t *v)
> static __always_inline s64
> arch_atomic64_read_acquire(const atomic64_t *v)
> {
> - return smp_load_acquire(&(v)->counter);
> + s64 ret;
> +
> + if (__native_word(atomic64_t)) {
> + ret = smp_load_acquire(&(v)->counter);
> + } else {
> + ret = arch_atomic64_read(v);
> + __atomic_acquire_fence();
> + }
> +
> + return ret;
> }
> #define arch_atomic64_read_acquire arch_atomic64_read_acquire
> #endif
> @@ -1267,7 +1290,12 @@ arch_atomic64_read_acquire(const atomic64_t *v)
> static __always_inline void
> arch_atomic64_set_release(atomic64_t *v, s64 i)
> {
> - smp_store_release(&(v)->counter, i);
> + if (__native_word(atomic64_t)) {
> + smp_store_release(&(v)->counter, i);
> + } else {
> + __atomic_release_fence();
> + arch_atomic64_set(v, i);
> + }
> }
> #define arch_atomic64_set_release arch_atomic64_set_release
> #endif
> @@ -2358,4 +2386,4 @@ arch_atomic64_dec_if_positive(atomic64_t *v)
> #endif
>
> #endif /* _LINUX_ATOMIC_FALLBACK_H */
> -// cca554917d7ea73d5e3e7397dd70c484cad9b2c4
> +// 8e2cc06bc0d2c0967d2f8424762bd48555ee40ae
> diff --git a/scripts/atomic/fallbacks/read_acquire b/scripts/atomic/fallbacks/read_acquire
> index 803ba7561076..a0ea1d26e6b2 100755
> --- a/scripts/atomic/fallbacks/read_acquire
> +++ b/scripts/atomic/fallbacks/read_acquire
> @@ -2,6 +2,15 @@ cat <<EOF
> static __always_inline ${ret}
> arch_${atomic}_read_acquire(const ${atomic}_t *v)
> {
> - return smp_load_acquire(&(v)->counter);
> + ${int} ret;
> +
> + if (__native_word(${atomic}_t)) {
> + ret = smp_load_acquire(&(v)->counter);
> + } else {
> + ret = arch_${atomic}_read(v);
> + __atomic_acquire_fence();
> + }
> +
> + return ret;
> }
> EOF
> diff --git a/scripts/atomic/fallbacks/set_release b/scripts/atomic/fallbacks/set_release
> index 86ede759f24e..05cdb7f42477 100755
> --- a/scripts/atomic/fallbacks/set_release
> +++ b/scripts/atomic/fallbacks/set_release
> @@ -2,6 +2,11 @@ cat <<EOF
> static __always_inline void
> arch_${atomic}_set_release(${atomic}_t *v, ${int} i)
> {
> - smp_store_release(&(v)->counter, i);
> + if (__native_word(${atomic}_t)) {
> + smp_store_release(&(v)->counter, i);
> + } else {
> + __atomic_release_fence();
> + arch_${atomic}_set(v, i);
> + }
> }
> EOF
> --
> 2.30.2
>
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next prev parent reply other threads:[~2022-02-04 0:20 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 16:12 Mark Rutland
2022-02-03 16:18 ` Ard Biesheuvel
2022-02-04 0:20 ` Boqun Feng [this message]
2022-02-04 11:16 ` Mark Rutland
2022-02-04 15:45 ` Boqun Feng
2022-02-06 14:06 ` Peter Zijlstra
2022-11-04 23:05 ` Thorsten Glaser
2022-11-07 10:37 ` Mark Rutland
2022-11-07 11:14 ` Thorsten Glaser
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