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From: Christian Brauner <christian.brauner@ubuntu.com>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: Chris Kennelly <ckennelly@google.com>,
	Peter Oskolkov <posk@google.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Peter Oskolkov <posk@posk.io>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	paulmck <paulmck@linux.ibm.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Paul Turner <pjt@google.com>,
	linux-api <linux-api@vger.kernel.org>, carlos <carlos@redhat.com>
Subject: Re: [RFC PATCH 2/4] rseq: Allow extending struct rseq
Date: Wed, 15 Jul 2020 12:59:43 +0200	[thread overview]
Message-ID: <20200715105943.3xbbwbzwc6drughf@wittgenstein> (raw)
In-Reply-To: <87k0z5xpau.fsf@mid.deneb.enyo.de>

On Wed, Jul 15, 2020 at 08:31:05AM +0200, Florian Weimer wrote:
> * Chris Kennelly:
> 
> > When glibc provides registration, is the anticipated use case that a
> > library would unregister and reregister each thread to "upgrade" it to
> > the most modern version of interface it knows about provided by the
> > kernel?
> 
> Absolutely not, that is likely to break other consumers because an
> expected rseq area becomes dormant instead.
> 
> > There, I could assume an all-or-nothing registration of the new
> > feature--limited only by kernel availability for thread
> > homogeneity--but inconsistencies across early adopter libraries would
> > mean each thread would have to examine its own TLS to determine if a
> > feature were available.

Fwiw, I pointed this out in the discussions that led up to this
patchset. I don't see how this can work if threads don't check for their
feature set.

> 
> Exactly.  Certain uses of seccomp can also have this effect,
> presenting a non-homogeneous view.

Good point. There might be threads with a seccomp filter that would
block rseq features is what you mean, I assume.

Christian

  reply	other threads:[~2020-07-15 10:59 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-14  3:03 [RFC PATCH 0/4] rseq: Introduce extensible struct rseq Mathieu Desnoyers
2020-07-14  3:03 ` [RFC PATCH 1/4] selftests: rseq: Use fixed value as rseq_len parameter Mathieu Desnoyers
2020-07-14  3:03 ` [RFC PATCH 2/4] rseq: Allow extending struct rseq Mathieu Desnoyers
2020-07-14  9:58   ` Florian Weimer
2020-07-14 12:50     ` Mathieu Desnoyers
2020-07-14 13:00       ` Florian Weimer
2020-07-14 13:19         ` Mathieu Desnoyers
2020-07-14 21:30           ` Carlos O'Donell
2020-07-15 13:12             ` Mathieu Desnoyers
2020-07-15 13:22               ` Florian Weimer
2020-07-15 13:31                 ` Mathieu Desnoyers
2020-07-15 13:42                   ` Florian Weimer
2020-07-15 13:55                     ` Christian Brauner
2020-07-15 14:20                       ` Mathieu Desnoyers
2020-07-15 14:54                     ` Mathieu Desnoyers
2020-07-15 14:58                       ` Florian Weimer
2020-07-15 15:26                         ` Mathieu Desnoyers
2020-07-14 17:24   ` Peter Oskolkov
2020-07-14 17:43     ` Mathieu Desnoyers
2020-07-14 18:33       ` Peter Oskolkov
2020-07-15  2:34         ` Chris Kennelly
2020-07-15  6:31           ` Florian Weimer
2020-07-15 10:59             ` Christian Brauner [this message]
2020-07-15 14:38             ` Mathieu Desnoyers
2020-07-15 14:50           ` Mathieu Desnoyers
2020-07-15 11:38   ` Christian Brauner
2020-07-15 12:33     ` Christian Brauner
2020-07-15 15:10       ` Mathieu Desnoyers
2020-07-15 15:33         ` Christian Brauner
2020-07-14  3:03 ` [RFC PATCH 3/4] selftests: rseq: define __rseq_abi with extensible size Mathieu Desnoyers
2020-07-14  3:03 ` [RFC PATCH 4/4] selftests: rseq: print rseq extensible size in basic test Mathieu Desnoyers
2020-07-14 20:55 ` [RFC PATCH 0/4] rseq: Introduce extensible struct rseq Carlos O'Donell
2020-07-15 13:02   ` Mathieu Desnoyers
2020-07-16 13:39     ` Carlos O'Donell
2020-07-16 14:45       ` Mathieu Desnoyers
2020-07-15 15:12   ` Florian Weimer
2020-07-15 15:32     ` Mathieu Desnoyers

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