Re: jump_label defaults (was Re: [patch 00/17] CFS BandwidthControl v7.1)

From: Peter Zijlstra
Date: Fri Jul 08 2011 - 05:20:59 EST


On Thu, 2011-07-07 at 22:36 +0200, Peter Zijlstra wrote:
> Hrm,. I can't seem to make that work, damn CPP for not being
> recursive.

Ha! the wonders of sleep, ok I can make this part work.

So how do we write this static_branch_true() thing?

But then I realized that if we do something like:

static __always_inline bool arch_static_branch(struct jump_label_key *key)
{
asm goto("1:"
JUMP_LABEL_INITIAL_NOP
".pushsection __jump_table, \"aw\" \n\t"
_ASM_ALIGN "\n\t"
_ASM_PTR "1b, %l[l_yes], %c0 \n\t"
".popsection \n\t"
: : "i" (key) : : l_yes);
return false;
l_yes:
return true;
}

Simply flipping the true and false in there isn't going to work, because
then its similar to !static_branch() and jump_label_inc() is going to
disable it.
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