From: Mark Rutland <mark.rutland@arm.com>
To: linux-kernel@vger.kernel.org
Cc: arnd@arndb.de, boqun.feng@gmail.com, peterz@infradead.org,
will@kernel.org, ardb@kernel.org
Subject: Re: [PATCH] atomics: fix atomic64_{read_acquire,set_release} fallbacks
Date: Thu, 3 Feb 2022 15:35:30 +0000 [thread overview]
Message-ID: <Yfv2Qgh/FYdGtQFj@FVFF77S0Q05N> (raw)
In-Reply-To: <20220203143848.3934515-1-mark.rutland@arm.com>
On Thu, Feb 03, 2022 at 02:38:48PM +0000, Mark Rutland wrote:
> @@ -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_atomic_read(v);
Ard pointed out on IRC that this is bogus, and should be using
arch_atomic64_read() ...
> + __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_atomic_set(v, i);
... and arch_atomic64_set() ...
> + }
> }
> #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
> +// ba488b6398359cb776d457971f30cef78d0d36dc
> diff --git a/scripts/atomic/fallbacks/read_acquire b/scripts/atomic/fallbacks/read_acquire
> index 803ba7561076..7b8b87143c0c 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);
... because this should be arch_${atomic}_read() ...
> + __atomic_acquire_fence();
> + }
> +
> + return ret;
> }
> EOF
> diff --git a/scripts/atomic/fallbacks/set_release b/scripts/atomic/fallbacks/set_release
> index 86ede759f24e..5f692db3ce29 100755
> --- a/scripts/atomic/fallbacks/set_release
> +++ b/scripts/atomic/fallbacks/set_release
> @@ -2,6 +2,11 @@ cat <<EOF
> static __always_inline void
> arch_${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);
... and this should be arch_${atomic}_set().
I'll spin a v2 with that corrected.
Thanks,
Mark.
next prev parent reply other threads:[~2022-02-03 15:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 14:38 Mark Rutland
2022-02-03 15:35 ` Mark Rutland [this message]
2022-02-03 16:09 ` kernel test robot
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