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From: Florian Weimer <fweimer@redhat.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: mathieu.desnoyers@efficios.com, David.Laight@aculab.com,
	alexander@mihalicyn.com, andrealmeid@igalia.com,
	boqun.feng@gmail.com, brauner@kernel.org, carlos@redhat.com,
	ckennelly@google.com, corbet@lwn.net, dave@stgolabs.net,
	dvhart@infradead.org, goldstein.w.n@gmail.com, hpa@zytor.com,
	libc-alpha@sourceware.org, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org, longman@redhat.com,
	mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org,
	pjt@google.com, posk@posk.io, rostedt@goodmis.org,
	tglx@linutronix.de
Subject: Re: [RFC PATCH v2 1/4] rseq: Add sched_state field to struct rseq
Date: Wed, 27 Sep 2023 06:51:37 +0200	[thread overview]
Message-ID: <875y3wp6au.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <CACT4Y+beLh1qnHF9bxhMUcva8KyuvZs7Mg_31SGK5xSoR=3m1A@mail.gmail.com> (Dmitry Vyukov's message of "Tue, 26 Sep 2023 16:49:32 -0700")

* Dmitry Vyukov:

> In reality it's a bit more involved since the field is actually 8
> bytes and only partially overlaps with rseq.cpu_id_start (it's an
> 8-byte pointer with high 4 bytes overlap rseq.cpu_id_start):
>
> https://github.com/google/tcmalloc/blob/229908285e216cca8b844c1781bf16b838128d1b/tcmalloc/internal/percpu.h#L101-L165

This does not compose with other rseq users, as noted in the sources:

  // Note: this makes __rseq_abi.cpu_id_start unusable for its original purpose.

For a core library such a malloc replacement, that is a very bad trap.

Thanks,
Florian


  parent reply	other threads:[~2023-09-27  5:17 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-29 19:14 [RFC PATCH v2 0/4] Extend rseq with sched_state_ptr field Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 1/4] rseq: Add sched_state field to struct rseq Mathieu Desnoyers
2023-05-29 19:35   ` Florian Weimer
2023-05-29 19:48     ` Mathieu Desnoyers
2023-05-30  8:20       ` Florian Weimer
2023-05-30 14:25         ` Mathieu Desnoyers
2023-05-30 15:13           ` Mathieu Desnoyers
2023-09-26 20:52       ` Dmitry Vyukov
2023-09-26 23:49         ` Dmitry Vyukov
2023-09-26 23:54           ` Dmitry Vyukov
2023-09-27  4:51           ` Florian Weimer [this message]
2023-09-27 15:58             ` Dmitry Vyukov
2023-09-28  8:52               ` Florian Weimer
2023-09-28 14:44                 ` Dmitry Vyukov
2023-09-28 14:47           ` Dmitry Vyukov
2023-09-28 10:39   ` Peter Zijlstra
2023-09-28 11:22     ` David Laight
2023-09-28 13:20       ` Mathieu Desnoyers
2023-09-28 14:26         ` Peter Zijlstra
2023-09-28 14:33         ` David Laight
2023-09-28 15:05         ` André Almeida
2023-09-28 14:43     ` Steven Rostedt
2023-09-28 15:51       ` David Laight
2023-10-02 16:51         ` Steven Rostedt
2023-10-02 17:22           ` David Laight
2023-10-02 17:56             ` Steven Rostedt
2023-09-28 20:21   ` Thomas Gleixner
2023-09-28 20:43     ` Mathieu Desnoyers
2023-09-28 20:54   ` Thomas Gleixner
2023-09-28 22:11     ` Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 2/4] selftests/rseq: Add sched_state rseq field and getter Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 3/4] selftests/rseq: Implement sched state test program Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 4/4] selftests/rseq: Implement rseq_mutex " Mathieu Desnoyers
2023-09-28 19:55   ` Thomas Gleixner

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