From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: carlos <carlos@redhat.com>,
Joseph Myers <joseph@codesourcery.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
libc-alpha <libc-alpha@sourceware.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ben Maurer <bmaurer@fb.com>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Will Deacon <will.deacon@arm.com>,
Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
Rich Felker <dalias@libc.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>
Subject: Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4)
Date: Mon, 14 Jan 2019 14:22:37 -0500 (EST) [thread overview]
Message-ID: <394676913.486.1547493757710.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <87fttv9iic.fsf@oldenburg2.str.redhat.com>
----- On Jan 14, 2019, at 10:55 AM, Florian Weimer fweimer@redhat.com wrote:
> * Mathieu Desnoyers:
>
>> Therefore, both symbols will end up in
>> sysdeps/unix/sysv/linux/Versions.
>
> I'm not sure what you mean by that. The physical location in the
> directory tree has little effect on which shared object the symbol is
> placed in; that will need other changes.
I'm currently moving the symbol definitions to csu/rseq-sym.c. On Linux,
its content is overridden by a new sysdeps/unix/sysv/linux/rseq-sym.c
which contains both __rseq_abi and __rseq_refcount symbols. On other
platforms, it is a stub file.
>>> By the way, you could avoid the need for unregistration if you allocated
>>> the rseq areas persistently, index by TID. They are quite small, so
>>> with the typical PID range, maybe the wasted memory due to changing TIDs
>>> would be acceptable?
>>
>> Would we be able to access those __rseq_abi as normal TLS IE model
>> variables ? The overhead of indexing an array matters for a
>> fast-path.
>
> No, that wouldn't be possible in this case. You would need another
> indirection.
Thanks for the clarification!
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2019-01-14 19:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-04 19:21 [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4) Mathieu Desnoyers
2018-12-04 19:21 ` [RFC PATCH glibc 2/4] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux Mathieu Desnoyers
2018-12-04 19:21 ` [RFC PATCH glibc 3/4] support record failure: allow use from constructor Mathieu Desnoyers
2018-12-04 19:21 ` [RFC PATCH glibc 4/4] rseq registration tests Mathieu Desnoyers
2018-12-04 19:44 ` [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4) Florian Weimer
2018-12-04 19:50 ` Mathieu Desnoyers
2018-12-11 10:40 ` Florian Weimer
2019-01-10 20:31 ` Mathieu Desnoyers
2019-01-11 1:11 ` Mathieu Desnoyers
2019-01-14 18:57 ` Florian Weimer
2019-01-14 18:55 ` Florian Weimer
2019-01-14 19:22 ` Mathieu Desnoyers [this message]
2019-01-14 19:37 ` Florian Weimer
2019-01-14 20:27 ` Mathieu Desnoyers
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