From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Dmitry Vyukov <dvyukov@google.com>,
Jinjie Ruan <ruanjinjie@huawei.com>,
linux-man@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Mark Rutland <mark.rutland@arm.com>,
Mathias Stearn <mathias@mongodb.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Boqun Feng <boqun.feng@gmail.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Chris Kennelly <ckennelly@google.com>,
regressions@lists.linux.dev, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Blake Oler <blake.oler@mongodb.com>
Subject: Re: [REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64 and tcmalloc everywhere
Date: Thu, 23 Apr 2026 08:29:39 -0400 [thread overview]
Message-ID: <1e839a25-d15f-40d3-ad6a-20469fb6137c@efficios.com> (raw)
In-Reply-To: <CACT4Y+bxnQyHGdVNE1BYTx+Z2-cscLb38HYS9jBM5gPAz8=4bw@mail.gmail.com>
On 2026-04-23 01:53, Dmitry Vyukov wrote:
[...]
> +linux-man
>
> This part of the rseq man page needs to be fixed as well I think. The
> kernel no longer reliably provides clearing of rseq_cs on preemption,
> right?
>
> https://git.kernel.org/pub/scm/libs/librseq/librseq.git/tree/doc/man/rseq.2#n241
I'm maintaining this manual page in librseq.
>
> "and set to NULL by the kernel when it restarts an assembly
> instruction sequence block,
> as well as when the kernel detects that it is preempting or delivering
> a signal outside of the range targeted by the rseq_cs."
I think you got two things confused here.
1) There is currently a bug on arm64 where it fails to honor the
rseq ABI contract wrt critical section abort. AFAIU there is a
fix proposed for this.
2) Thomas relaxed the implementation of cpu_id_start field updates
so it only stores to the rseq area when the current cpu actually
changes (migration).
So AFAIU the statement in the man page is still fine. It's just arm64
that needs fixing.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
next prev parent reply other threads:[~2026-04-23 12:30 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAHnCjA25b+nO2n5CeifknSKHssJpPrjnf+dtr7UgzRw4Zgu=oA@mail.gmail.com>
2026-04-22 12:56 ` [REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64 and tcmalloc everywhere Peter Zijlstra
2026-04-22 13:13 ` Peter Zijlstra
2026-04-23 10:38 ` Mathias Stearn
[not found] ` <CAHnCjA2fa+dP1+yCYNQrTXQaW-JdtfMj7wMikwMeeCRg-3NhiA@mail.gmail.com>
2026-04-23 11:48 ` Thomas Gleixner
2026-04-23 12:11 ` Mathias Stearn
2026-04-23 17:19 ` Thomas Gleixner
2026-04-23 17:38 ` Chris Kennelly
2026-04-23 17:47 ` Mathieu Desnoyers
2026-04-23 19:39 ` Thomas Gleixner
2026-04-23 17:41 ` Linus Torvalds
2026-04-23 18:35 ` Mathias Stearn
2026-04-23 18:53 ` Mark Rutland
2026-04-23 21:03 ` Thomas Gleixner
2026-04-23 21:28 ` Linus Torvalds
2026-04-23 23:08 ` Linus Torvalds
2026-04-27 7:06 ` Florian Weimer
2026-04-27 16:12 ` Linus Torvalds
2026-04-22 13:09 ` Mark Rutland
2026-04-22 17:49 ` Thomas Gleixner
2026-04-22 18:11 ` Mark Rutland
2026-04-22 19:47 ` Thomas Gleixner
2026-04-23 1:48 ` Jinjie Ruan
2026-04-23 5:53 ` Dmitry Vyukov
2026-04-23 10:39 ` Thomas Gleixner
2026-04-23 10:51 ` Mathias Stearn
2026-04-23 12:24 ` David Laight
2026-04-23 19:31 ` Thomas Gleixner
2026-04-24 7:56 ` Dmitry Vyukov
2026-04-24 8:32 ` Mathias Stearn
2026-04-24 9:30 ` Dmitry Vyukov
2026-04-24 14:16 ` Thomas Gleixner
2026-04-24 15:03 ` Peter Zijlstra
2026-04-24 19:44 ` Thomas Gleixner
2026-04-26 22:04 ` Thomas Gleixner
2026-04-27 7:40 ` Florian Weimer
2026-04-27 11:03 ` Thomas Gleixner
2026-04-27 18:35 ` Mathieu Desnoyers
2026-04-27 21:06 ` Thomas Gleixner
2026-04-28 6:11 ` Dmitry Vyukov
2026-04-28 8:07 ` Thomas Gleixner
2026-04-28 8:18 ` Thomas Gleixner
[not found] ` <CACT4Y+b_RH2eZMuh1YUyqnoK-5KUpdWW4z1q2ZQWkY_GcBqmNw@mail.gmail.com>
[not found] ` <CAHnCjA2sCwOumOjWm=wW=Kj0C83KVW5zS+51=9=YSeAzuEaVQA@mail.gmail.com>
2026-04-28 15:46 ` Thomas Gleixner
2026-04-28 7:39 ` Peter Zijlstra
2026-04-28 8:13 ` Peter Zijlstra
2026-04-28 8:51 ` Thomas Gleixner
2026-04-28 8:03 ` Peter Zijlstra
2026-04-28 8:36 ` Thomas Gleixner
2026-04-23 12:11 ` Alejandro Colomar
2026-04-23 12:54 ` Mathieu Desnoyers
2026-04-23 12:29 ` Mathieu Desnoyers [this message]
2026-04-23 12:36 ` Dmitry Vyukov
2026-04-23 12:53 ` Mathieu Desnoyers
2026-04-23 12:58 ` Dmitry Vyukov
2026-04-24 16:45 ` [PATCH] arm64/entry: Fix arm64-specific rseq brokenness (was: Re: [REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64) " Mark Rutland
2026-04-28 1:39 ` [PATCH] arm64/entry: Fix arm64-specific rseq brokenness Jinjie Ruan
2026-04-28 13:40 ` Mark Rutland
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