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From: Florian Weimer <fweimer@redhat.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.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 19:55:07 +0100	[thread overview]
Message-ID: <87fttv9iic.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <1681283664.1380.1547152315426.JavaMail.zimbra@efficios.com> (Mathieu Desnoyers's message of "Thu, 10 Jan 2019 15:31:55 -0500 (EST)")

* 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.

>> 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,
Florian

  parent reply	other threads:[~2019-01-14 18:55 UTC|newest]

Thread overview: 12+ 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 19:44 ` [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 [this message]
2019-01-14 19:22       ` Mathieu Desnoyers
2019-01-14 19:37         ` Florian Weimer
2019-01-14 20:27           ` Mathieu Desnoyers

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