From: Joseph Myers <joseph@codesourcery.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: carlos <carlos@redhat.com>, Florian Weimer <fweimer@redhat.com>,
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>,
libc-alpha <libc-alpha@sourceware.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>
Subject: Re: [RFC PATCH] glibc: Perform rseq(2) registration at nptl init and thread creation
Date: Thu, 20 Sep 2018 20:20:28 +0000 [thread overview]
Message-ID: <alpine.DEB.2.21.1809202016270.17228@digraph.polyomino.org.uk> (raw)
In-Reply-To: <1619649568.9014.1537474457166.JavaMail.zimbra@efficios.com>
On Thu, 20 Sep 2018, Mathieu Desnoyers wrote:
> Are you saying glibc has an explicit check for the kernel version visible
> from /proc before using specific features ? If so, how can this work with
> the variety of feature backports we find in the distribution kernels out
> there ?
See sysdeps/unix/sysv/linux/dl-sysdep.c and
sysdeps/unix/sysv/linux/dl-osinfo.h. As I said, Carlos has proposed
removing that check.
> For too-old headers at compile time, one possibility is that we don't event
> expose the __rseq_abi TLS symbol. OTOH, if we need to keep exposing it anyway
> for ABI consistency purposes, then we'd leave its cpu_id field at the initial
> value (-1). But that would require that we copy linux/rseq.h into the glibc
> source tree.
The ABI needs to be independent of the kernel headers used. I don't think
you need to copy linux/rseq.h; all you should need is to e.g. define an
array of suitable size and alignment with the relevant member initialized
and a suitable explanatory comment.
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2018-09-20 20:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-19 14:44 [RFC PATCH] glibc: Perform rseq(2) registration at nptl init and thread creation Mathieu Desnoyers
2018-09-19 16:37 ` Joseph Myers
2018-09-19 16:37 ` Joseph Myers
2018-09-19 16:53 ` Mathieu Desnoyers
2018-09-19 17:10 ` Joseph Myers
2018-09-20 20:14 ` Mathieu Desnoyers
2018-09-20 20:20 ` Joseph Myers [this message]
2018-09-21 16:29 ` Mathieu Desnoyers
2018-09-20 20:04 ` Mathieu Desnoyers
2018-09-20 20:29 ` Joseph Myers
2018-09-19 17:38 ` Szabolcs Nagy
2018-09-19 19:49 ` Joseph Myers
2018-09-19 19:49 ` Joseph Myers
2018-09-19 20:10 ` Mathieu Desnoyers
2018-09-19 21:01 ` Mathieu Desnoyers
2018-09-20 10:28 ` Szabolcs Nagy
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