Re: Restartable Sequences system call merged into Linux

From: Florian Weimer <fweimer@redhat.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Pavel Machek <pavel@ucw.cz>
Cc: 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: Fri, 15 Jun 2018 07:09:42 +0200	[thread overview]
Message-ID: <b5c0a91b-b428-7807-0f16-97f15e632bdb@redhat.com> (raw)
In-Reply-To: <894222691.12973.1528981314012.JavaMail.zimbra@efficios.com>

On 06/14/2018 03:01 PM, Mathieu Desnoyers wrote:
> Another alternative would be to somehow let glibc handle the registration,
> perhaps only doing it for applications expressing their interest for rseq.

That's not really possible.  We can't rely on the visibility of symbol 
bindings due to lazy binding and hidden visibility.  Registration of 
intent by other means will not work because if it is done from user 
code, some other library may have already launched a thread at this point.

(It's also a moot point if we want to use restartable sequences in glibc 
itself.)

Thanks,
Florian