From: Catalin Marinas <catalin.marinas@arm.com>
To: Ankur Arora <ankur.a.arora@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org,
bpf@vger.kernel.org, arnd@arndb.de, will@kernel.org,
peterz@infradead.org, akpm@linux-foundation.org,
mark.rutland@arm.com, harisokn@amazon.com, cl@gentwo.org,
ast@kernel.org, rafael@kernel.org, daniel.lezcano@linaro.org,
memxor@gmail.com, zhenglifeng1@huawei.com,
xueshuai@linux.alibaba.com, joao.m.martins@oracle.com,
boris.ostrovsky@oracle.com, konrad.wilk@oracle.com
Subject: Re: [PATCH v9 04/12] arm64: support WFET in smp_cond_load_relaxed_timeout()
Date: Wed, 11 Feb 2026 17:11:23 +0000 [thread overview]
Message-ID: <aYy4O66B6T63tRaa@arm.com> (raw)
In-Reply-To: <20260209023153.2661784-5-ankur.a.arora@oracle.com>
On Sun, Feb 08, 2026 at 06:31:45PM -0800, Ankur Arora wrote:
> diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
> index d7a540736741..dfb7d10a18be 100644
> --- a/arch/arm64/include/asm/cmpxchg.h
> +++ b/arch/arm64/include/asm/cmpxchg.h
> @@ -12,6 +12,7 @@
>
> #include <asm/barrier.h>
> #include <asm/lse.h>
> +#include <asm/delay-const.h>
>
> /*
> * We need separate acquire parameters for ll/sc and lse, since the full
> @@ -208,9 +209,13 @@ __CMPXCHG_GEN(_mb)
> __cmpxchg128((ptr), (o), (n)); \
> })
>
> +/* Re-declared here to avoid include dependency. */
> +extern u64 (*arch_timer_read_counter)(void);
We have a bug in udelay() because the above might read the physical
counter while WFET uses the virtual one. See this thread:
https://lore.kernel.org/all/ktosachvft2cgqd5qkukn275ugmhy6xrhxur4zqpdxlfr3qh5h@o3zrfnsq63od/
We could use __arch_counter_get_cntvct_stable() as in Marc's suggestion
for the udelay() fix (or just wait to see the outcome of the above
thread).
The rest looks fine.
--
Catalin
next prev parent reply other threads:[~2026-02-11 17:11 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-09 2:31 [PATCH v9 00/12] barrier: Add smp_cond_load_{relaxed,acquire}_timeout() Ankur Arora
2026-02-09 2:31 ` [PATCH v9 01/12] asm-generic: barrier: Add smp_cond_load_relaxed_timeout() Ankur Arora
2026-02-09 4:57 ` Randy Dunlap
2026-02-10 5:52 ` Ankur Arora
2026-02-11 15:39 ` Catalin Marinas
2026-02-11 22:17 ` Ankur Arora
2026-02-12 9:56 ` David Laight
2026-02-14 4:58 ` Ankur Arora
2026-02-14 11:31 ` David Laight
2026-02-18 6:33 ` Ankur Arora
2026-02-09 2:31 ` [PATCH v9 02/12] arm64: barrier: Support smp_cond_load_relaxed_timeout() Ankur Arora
2026-02-11 15:54 ` Catalin Marinas
2026-02-11 22:57 ` Ankur Arora
2026-02-09 2:31 ` [PATCH v9 03/12] arm64/delay: move some constants out to a separate header Ankur Arora
2026-02-11 16:01 ` Catalin Marinas
2026-02-09 2:31 ` [PATCH v9 04/12] arm64: support WFET in smp_cond_load_relaxed_timeout() Ankur Arora
2026-02-11 17:11 ` Catalin Marinas [this message]
2026-02-11 23:13 ` Ankur Arora
2026-02-09 2:31 ` [PATCH v9 05/12] arm64: rqspinlock: Remove private copy of smp_cond_load_acquire_timewait() Ankur Arora
2026-02-09 2:31 ` [PATCH v9 06/12] asm-generic: barrier: Add smp_cond_load_acquire_timeout() Ankur Arora
2026-02-09 4:59 ` Randy Dunlap
2026-02-09 2:31 ` [PATCH v9 07/12] atomic: Add atomic_cond_read_*_timeout() Ankur Arora
2026-02-11 17:25 ` Catalin Marinas
2026-02-09 2:31 ` [PATCH v9 08/12] locking/atomic: scripts: build atomic_long_cond_read_*_timeout() Ankur Arora
2026-02-11 17:41 ` Catalin Marinas
2026-02-09 2:31 ` [PATCH v9 09/12] bpf/rqspinlock: switch check_timeout() to a clock interface Ankur Arora
2026-02-09 3:05 ` bot+bpf-ci
2026-02-09 2:31 ` [PATCH v9 10/12] bpf/rqspinlock: Use smp_cond_load_acquire_timeout() Ankur Arora
2026-02-09 2:31 ` [PATCH v9 11/12] sched: add need-resched timed wait interface Ankur Arora
2026-02-09 3:05 ` bot+bpf-ci
2026-02-09 2:31 ` [PATCH v9 12/12] cpuidle/poll_state: Wait for need-resched via tif_need_resched_relaxed_wait() Ankur Arora
2026-02-10 16:55 ` Rafael J. Wysocki
2026-02-11 0:29 ` Ankur Arora
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