From: Jason Baron <jbaron@redhat.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
"David S. Miller" <davem@davemloft.net>,
David Daney <david.daney@cavium.com>,
Michael Ellerman <michael@ellerman.id.au>,
Jan Glauber <jang@linux.vnet.ibm.com>,
the arch/x86 maintainers <x86@kernel.org>,
Xen Devel <xen-devel@lists.xensource.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Subject: Re: [PATCH RFC V2 3/5] jump_label: if a key has already been initialized, don't nop it out
Date: Mon, 10 Oct 2011 16:10:28 -0400 [thread overview]
Message-ID: <20111010201027.GC2413@redhat.com> (raw)
In-Reply-To: <4E934E5B.3000603@goop.org>
On Mon, Oct 10, 2011 at 12:58:19PM -0700, Jeremy Fitzhardinge wrote:
> > Hi,
> >
> > I just realized that the early call to jump_label_inc(), isn't being
> > honored with this patch until later when we invoke jump_label_init().
> > That strikes me as being inconsistent. When jump_label_inc() returns we
> > should expect the branch to be updated.
>
> Why is that? It looks to me like it will unconditionally update the
> instruction, irrespective of whether _init() has been called?
>
No. jump_label_init(), sets up key->entries, to point into the jump
table...before that jump_label_update(), doesn't know where the table is
located, and will just return, without doing the update.
> > Thus, I think what probably want is to add a new 'int jump_label_init'
> > flag. If its not set we can call 'jump_label_init()' from
> > jump_label_inc()/dec().
>
> Hm. I worry that it may end up calling jump_label_init() in an
> unexpected context, especially since it may well be config-dependent, or
> adding a jump_label_inc() later on starts mysteriously failing.
good point.
>
> > And jump_label_init() can avoid initialization
> > if its already set.
>
> That doesn't seem worthwhile in itself. I suspect the number of "early"
> jump_label_incs will be very small (or we should look at doing the init
> earlier).
>
> J
I have it as 'early_initcall()', but perhaps it should be moved into
init/main.c. I don't think there's any reason it can't be done super
early. So I think this might be the best answer. It will also simplify
your series.
Thanks,
-Jason
next prev parent reply other threads:[~2011-10-10 20:10 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-01 21:55 [PATCH RFC V2 0/5] jump-label: allow early jump_label_enable() Jeremy Fitzhardinge
2011-10-01 21:55 ` [PATCH RFC V2 1/5] jump_label: use proper atomic_t initializer Jeremy Fitzhardinge
2011-10-01 21:55 ` [PATCH RFC V2 2/5] stop_machine: make stop_machine safe and efficient to call early Jeremy Fitzhardinge
2011-10-02 0:36 ` Tejun Heo
2011-10-03 19:24 ` [Xen-devel] " Konrad Rzeszutek Wilk
2011-10-01 21:55 ` [PATCH RFC V2 3/5] jump_label: if a key has already been initialized, don't nop it out Jeremy Fitzhardinge
2011-10-03 15:02 ` Jason Baron
2011-10-03 15:47 ` Steven Rostedt
2011-10-03 16:27 ` Jeremy Fitzhardinge
2011-10-04 14:10 ` Jason Baron
2011-10-04 15:18 ` Jeremy Fitzhardinge
2011-10-04 16:30 ` H. Peter Anvin
2011-10-04 17:53 ` Jason Baron
2011-10-04 18:05 ` Steven Rostedt
2011-10-06 0:16 ` Jeremy Fitzhardinge
2011-10-06 0:17 ` H. Peter Anvin
2011-10-06 0:47 ` Jeremy Fitzhardinge
2011-10-06 17:53 ` Jeremy Fitzhardinge
2011-10-06 18:10 ` Jason Baron
2011-10-06 18:13 ` H. Peter Anvin
2011-10-06 21:39 ` Jeremy Fitzhardinge
2011-10-06 22:08 ` Steven Rostedt
2011-10-06 18:15 ` Jeremy Fitzhardinge
2011-10-06 18:33 ` Jason Baron
2011-10-06 18:35 ` H. Peter Anvin
2011-10-06 18:43 ` Jason Baron
2011-10-06 18:26 ` Steven Rostedt
2011-10-06 18:29 ` H. Peter Anvin
2011-10-06 18:38 ` Jason Baron
2011-10-06 19:34 ` Steven Rostedt
2011-10-06 20:33 ` Jason Baron
2011-10-06 20:45 ` Steven Rostedt
2011-10-06 18:50 ` Richard Henderson
2011-10-06 19:28 ` Steven Rostedt
2011-10-06 21:42 ` Jeremy Fitzhardinge
2011-10-06 22:06 ` Steven Rostedt
2011-10-06 22:10 ` Jeremy Fitzhardinge
2011-10-06 22:20 ` Steven Rostedt
2011-10-07 17:09 ` [PATCH][RFC] jump_labels/x86: Use either 5 byte or 2 byte jumps Steven Rostedt
2011-10-07 18:52 ` Jason Baron
2011-10-07 19:21 ` Steven Rostedt
2011-10-07 21:48 ` H. Peter Anvin
2011-10-07 22:00 ` Steven Rostedt
2011-10-07 22:03 ` H. Peter Anvin
2011-10-07 19:33 ` Steven Rostedt
2011-10-07 19:40 ` Jeremy Fitzhardinge
2011-10-07 19:58 ` Steven Rostedt
2011-10-07 20:04 ` Peter Zijlstra
2011-10-10 15:36 ` [PATCH RFC V2 3/5] jump_label: if a key has already been initialized, don't nop it out Jason Baron
2011-10-10 19:58 ` Jeremy Fitzhardinge
2011-10-10 20:10 ` Jason Baron [this message]
2011-10-01 21:55 ` [PATCH RFC V2 4/5] x86/jump_label: drop arch_jump_label_text_poke_early() Jeremy Fitzhardinge
2011-10-01 21:55 ` [PATCH RFC V2 5/5] sparc/jump_label: " Jeremy Fitzhardinge
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