Messages in this thread | | | Subject | Re: Jump Label initialization | From | Peter Zijlstra <> | Date | Thu, 29 Sep 2011 09:37:59 +0200 |
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On Wed, 2011-09-28 at 19:14 -0700, Jeremy Fitzhardinge wrote: > Hi all, > > I'm trying to use the jump label machinery as part of the pv ticketlock > work I'm doing on x86. > > The problem I'm having at the moment is that I do my spinlock setup in > smp_prepare_boot_cpu(), which happens before jump_label_init() gets > called, and so the latter goes and nops out all my enabled jump label key. > > I'm experimenting at the moment with a patch to allow > jump_label_enable() to be called fairly early, and have that be > respected by jump_label_init(). I'm doing this by replacing > arch_jump_label_poke_text_early() with > arch_jump_label_transform_early(), which shares most of its code with > its non-early variant, except that it expects to run in a pre-SMP > environment. > > Does this seem plausible? (I haven't tested it yet.) > > The x86, mips and sparc patches are fairly simple; I forgot to look at > powerpc, and I didn't fully investigate s390. > > While my current use-case is x86-specific, it seems generally useful to > make the jump_label machinery available as early as possible. I wonder > if you have any suggestions about how to handle this?
I also remember talking to Jason about a way to initialize a jump label enabled, instead of the default disabled.
So yeah, I think your stuff would be useful..
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