From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>, bigeasy@linutronix.de
Cc: mark.rutland@arm.com, maz@kernel.org, catalin.marinas@arm.com,
will@kernel.org, chenhuacai@kernel.org, kernel@xen0n.name,
hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com,
borntraeger@linux.ibm.com, svens@linux.ibm.com,
pbonzini@redhat.com, wanpengli@tencent.com, vkuznets@redhat.com,
mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
x86@kernel.org, hpa@zytor.com, jgross@suse.com,
boris.ostrovsky@oracle.com, daniel.lezcano@linaro.org,
kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, rafael@kernel.org, peterz@infradead.org,
longman@redhat.com, boqun.feng@gmail.com, pmladek@suse.com,
senozhatsky@chromium.org, rostedt@goodmis.org,
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bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
vschneid@redhat.com, jstultz@google.com, sboyd@kernel.org,
linux-kernel@vger.kernel.org, loongarch@lists.linux.dev,
linux-s390@vger.kernel.org, kvm@vger.kernel.org,
linux-hyperv@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [RFC][PATCH 1/9] seqlock/latch: Provide raw_read_seqcount_latch_retry()
Date: Tue, 09 May 2023 10:13:20 +0200 [thread overview]
Message-ID: <871qjp3otb.ffs@tglx> (raw)
In-Reply-To: <20230508213147.448097252@infradead.org>
On Mon, May 08 2023 at 23:19, Peter Zijlstra wrote:
> The read side of seqcount_latch consists of:
>
> do {
> seq = raw_read_seqcount_latch(&latch->seq);
> ...
> } while (read_seqcount_latch_retry(&latch->seq, seq));
>
> which is asymmetric in the raw_ department, and sure enough,
> read_seqcount_latch_retry() includes (explicit) instrumentation where
> raw_read_seqcount_latch() does not.
>
> This inconsistency becomes a problem when trying to use it from
> noinstr code. As such, fix it by renaming and re-implementing
> raw_read_seqcount_latch_retry() without the instrumentation.
>
> Specifically the instrumentation in question is kcsan_atomic_next(0)
> in do___read_seqcount_retry(). Loosing this annotation is not a
> problem because raw_read_seqcount_latch() does not pass through
> kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX).
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
next prev parent reply other threads:[~2023-05-09 8:13 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-08 21:19 [RFC][PATCH 0/9] local_clock() vs noinstr Peter Zijlstra
2023-05-08 21:19 ` [RFC][PATCH 1/9] seqlock/latch: Provide raw_read_seqcount_latch_retry() Peter Zijlstra
2023-05-09 8:13 ` Thomas Gleixner [this message]
2023-05-10 7:58 ` Petr Mladek
2023-05-08 21:19 ` [RFC][PATCH 2/9] time/sched_clock: Provide sched_clock_noinstr() Peter Zijlstra
2023-05-08 21:19 ` [RFC][PATCH 3/9] arm64/io: Always inline all of __raw_{read,write}[bwlq]() Peter Zijlstra
2023-05-09 14:51 ` Mark Rutland
2023-05-08 21:19 ` [RFC][PATCH 4/9] arm64/arch_timer: Provide noinstr sched_clock_read() functions Peter Zijlstra
2023-05-08 21:19 ` [RFC][PATCH 5/9] loongarch: Provide noinstr sched_clock_read() Peter Zijlstra
2023-05-08 21:19 ` [RFC][PATCH 6/9] s390/time: Provide sched_clock_noinstr() Peter Zijlstra
2023-05-09 6:13 ` Heiko Carstens
2023-05-09 6:42 ` Peter Zijlstra
2023-05-08 21:19 ` [RFC][PATCH 7/9] x86/tsc: " Peter Zijlstra
2023-05-08 21:44 ` Peter Zijlstra
2023-05-08 23:30 ` Wei Liu
2023-05-11 20:23 ` Peter Zijlstra
2023-05-11 23:11 ` Michael Kelley (LINUX)
2023-05-12 6:00 ` Peter Zijlstra
2023-05-17 2:26 ` Michael Kelley (LINUX)
2023-05-17 11:13 ` Peter Zijlstra
2023-05-08 21:19 ` [RFC][PATCH 8/9] sched/clock: Provide local_clock_noinstr() Peter Zijlstra
2023-05-08 21:20 ` [RFC][PATCH 9/9] cpuidle: Use local_clock_noinstr() Peter Zijlstra
2023-05-09 16:18 ` Rafael J. Wysocki
2023-05-09 19:02 ` Peter Zijlstra
2023-05-10 13:43 ` [RFC][PATCH 0/9] local_clock() vs noinstr Sebastian Andrzej Siewior
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