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Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4)
- From: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: carlos <carlos at redhat dot com>, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha <libc-alpha at sourceware dot org>, Thomas Gleixner <tglx at linutronix dot de>, Ben Maurer <bmaurer at fb dot com>, Peter Zijlstra <peterz at infradead dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Boqun Feng <boqun dot feng at gmail dot com>, Will Deacon <will dot deacon at arm dot com>, Dave Watson <davejwatson at fb dot com>, Paul Turner <pjt at google dot com>, Rich Felker <dalias at libc dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, linux-api <linux-api at vger dot kernel dot org>
- Date: Thu, 10 Jan 2019 20:11:56 -0500 (EST)
- Subject: Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4)
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- References: <20181204192141.4684-1-mathieu.desnoyers@efficios.com> <87h8fkz6qx.fsf@oldenburg2.str.redhat.com> <1681283664.1380.1547152315426.JavaMail.zimbra@efficios.com>
----- On Jan 10, 2019, at 12:31 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
> ----- On Dec 11, 2018, at 2:40 AM, Florian Weimer fweimer@redhat.com wrote:
[...]
>>
>>> diff --git a/nptl/Versions b/nptl/Versions
>>> index e7f691da7a..f7890f73fc 100644
>>> --- a/nptl/Versions
>>> +++ b/nptl/Versions
>>> @@ -277,6 +277,10 @@ libpthread {
>>> cnd_timedwait; cnd_wait; tss_create; tss_delete; tss_get; tss_set;
>>> }
>>>
>>> + GLIBC_2.29 {
>>> + __rseq_refcount;
>>> + }
>>
>> Why put this into libpthread, and __rseq_abi into libc?
>
> The __rseq_abi symbol should be available to the glibc memory allocator.
> I plan to move the __rseq_abi to sysdeps/unix/sysv/linux/Versions instead
> so it becomes Linux-specific.
>
> The __rseq_refcount symbol only needs to be made available to applications
> and libraries linking against libpthread, because only libpthread actually
> handles the rseq registration/unregistration at thread start/exit and
> library initialization.
>
> However, considering that we want this to be Linux-specific as well,
> I could move it to sysdeps/unix/sysv/linux/Versions too.
>
> Then it would make sense to move the __rseq_refcount symbol defined in
> nptl/rseq.c to sysdeps/unix/sysv/linux/rseq.c as well and group
> everything together.
>
> Therefore, both symbols will end up in sysdeps/unix/sysv/linux/Versions.
Now that I think about it, it's important to move the rseq registration
done at nptl init (in my current code) to some lower-level csu initialiation,
so applications that happen _not_ to link against libpthread also get
registered rseq for the main thread.
Does it make sense ?
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com