Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 8 Jul 2015 10:37:55 -0700 | Subject | Re: Kernel broken on processors without performance counters |
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On Wed, Jul 8, 2015 at 9:07 AM, Peter Zijlstra <peterz@infradead.org> wrote: > On Wed, Jul 08, 2015 at 11:17:38AM -0400, Mikulas Patocka wrote: >> Hi >> >> I found out that the patch a66734297f78707ce39d756b656bfae861d53f62 breaks >> the kernel on processors without performance counters, such as AMD K6-3. >> Reverting the patch fixes the problem. >> >> The static key rdpmc_always_available somehow gets set (I couldn't really >> find out what is setting it, the function set_attr_rdpmc is not executed), >> cr4_set_bits(X86_CR4_PCE) is executed and that results in a crash on boot >> when attempting to execute init, because the proecssor doesn't support >> that bit in CR4. > > Urgh, the static key trainwreck bites again. > > One is not supposed to mix static_key_true() and STATIC_KEY_INIT_FALSE. > > Does this make it go again? > > --- > arch/x86/include/asm/mmu_context.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h > index 5e8daee7c5c9..804a3a6030ca 100644 > --- a/arch/x86/include/asm/mmu_context.h > +++ b/arch/x86/include/asm/mmu_context.h > @@ -23,7 +23,7 @@ extern struct static_key rdpmc_always_available; > > static inline void load_mm_cr4(struct mm_struct *mm) > { > - if (static_key_true(&rdpmc_always_available) || > + if (static_key_false(&rdpmc_always_available) ||
In what universe is "static_key_false" a reasonable name for a function that returns true if a static key is true?
Can we rename that function? And could we maybe make static keys type safe? I.e. there would be a type that starts out true and a type that starts out false.
--Andy
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