From: Pavel Machek <pavel@ucw.cz>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Florian Weimer <fweimer@redhat.com>, carlos <carlos@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
libc-alpha <libc-alpha@sourceware.org>
Subject: Re: Restartable Sequences system call merged into Linux
Date: Thu, 14 Jun 2018 12:28:00 -0000 [thread overview]
Message-ID: <20180614122759.GB8798@amd> (raw)
In-Reply-To: <417742741.11550.1528821084084.JavaMail.zimbra@efficios.com>
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On Tue 2018-06-12 12:31:24, Mathieu Desnoyers wrote:
> ----- On Jun 12, 2018, at 9:11 AM, Florian Weimer fweimer@redhat.com wrote:
>
> > On 06/11/2018 10:04 PM, Mathieu Desnoyers wrote:
> >> ----- On Jun 11, 2018, at 3:55 PM, Florian Weimer fweimer@redhat.com wrote:
> >>
> >>> On 06/11/2018 09:49 PM, Mathieu Desnoyers wrote:
> >>>> It should be noted that there can be only one rseq TLS area registered per
> >>>> thread,
> >>>> which can then be used by many libraries and by the executable, so this is a
> >>>> process-wide (per-thread) resource that we need to manage carefully.
> >>>
> >>> Is it possible to resize the area after thread creation, perhaps even
> >>> from other threads?
> >>
> >> I'm not sure why we would want to resize it. The per-thread area is fixed-size.
> >> Its layout is here: include/uapi/linux/rseq.h: struct rseq
> >
> > Looks I was mistaken and this is very similar to the robust mutex list.
> >
> > Should we treat it the same way? Always allocate it for each new thread
> > and register it with the kernel?
>
> That would be an efficient way to do it, indeed. There is very little
> performance overhead to have rseq registered for all threads, whether or
> not they intend to run rseq critical sections.
People with slow / low memory machines would prefer not to see
overhead they don't need...
> I have a few possible approaches in mind (feel free to suggest other
> options):
>
> A) glibc exposes a strong __rseq_abi TLS symbol:
>
> - should ideally *not* be global-dynamic for performance reasons,
> - registration to kernel can either be handled explicitly by requiring
> application or libraries to call an API, or implicitly at thread
> creation,
...so I'd prefer explicit API call.
> B) librseq.so exposes a strong __rseq_abi symbol:
Works for me.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2018-06-14 12:28 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-11 19:49 Mathieu Desnoyers
2018-06-11 19:55 ` Florian Weimer
2018-06-11 20:04 ` Mathieu Desnoyers
2018-06-12 13:11 ` Florian Weimer
2018-06-12 16:31 ` Mathieu Desnoyers
2018-06-13 8:23 ` Florian Weimer
2018-06-14 12:28 ` Pavel Machek [this message]
2018-06-14 13:02 ` Mathieu Desnoyers
2018-06-14 13:26 ` Pavel Machek
2018-06-14 13:32 ` Florian Weimer
2018-06-14 13:46 ` Mathieu Desnoyers
2018-06-15 5:10 ` Florian Weimer
2018-06-15 17:44 ` Mathieu Desnoyers
2018-06-14 13:38 ` Mathieu Desnoyers
2018-06-14 13:50 ` Pavel Machek
2018-06-14 14:01 ` Florian Weimer
2018-06-14 14:36 ` Mathieu Desnoyers
2018-06-14 14:41 ` Florian Weimer
2018-06-14 15:09 ` Mathieu Desnoyers
2018-06-15 5:09 ` Florian Weimer
2018-06-15 17:50 ` Mathieu Desnoyers
2018-06-15 5:07 ` Florian Weimer
2018-06-13 11:48 ` Heiko Carstens
2018-06-13 16:14 ` Mathieu Desnoyers
2018-06-13 19:53 ` Mathieu Desnoyers
2018-07-11 16:03 ` Stefan Liebler
2018-07-11 16:23 ` Adhemerval Zanella
2018-07-11 17:19 ` Florian Weimer
2018-07-11 17:42 ` Adhemerval Zanella
2018-07-11 17:45 ` Florian Weimer
2018-07-11 17:59 ` Adhemerval Zanella
2018-07-12 8:08 ` Stefan Liebler
2018-07-11 19:05 ` Carlos O'Donell
2018-07-12 8:10 ` Szabolcs Nagy
2018-07-13 13:22 ` Stefan Liebler
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