From: Dmitry Vyukov <dvyukov@google.com>
To: Florian Weimer <fweimer@redhat.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 08:58:16 -0700 [thread overview]
Message-ID: <CACT4Y+aVY+KPmBXYDBpA+JmLHvk=o5bt9d4tV5L41e813e0SVw@mail.gmail.com> (raw)
In-Reply-To: <875y3wp6au.fsf@oldenburg.str.redhat.com>
On Tue, 26 Sept 2023 at 21:51, Florian Weimer <fweimer@redhat.com> wrote:
>
> * 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.
I agree. I wouldn't do this if there were other options. That's why I
am looking for official kernel support for this.
If we would have a separate 8 bytes that are overwritten with 0 when a
thread is descheduled, that would be perfect.
next prev parent reply other threads:[~2023-09-27 15:58 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
2023-09-27 15:58 ` Dmitry Vyukov [this message]
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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