Messages in this thread | | | Subject | Re: [patch 5/9] Conditional Calls - i386 Optimization | From | Andi Kleen <> | Date | 31 May 2007 15:54:32 +0200 |
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Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> writes:
> +#define cond_call_optimized(flags, name, func) \ > + ({ \ > + static const char __cstrtab_name_##name[] \ > + __attribute__((section("__cond_call_strings"))) = #name; \ > + char condition; \ > + asm ( ".section __cond_call, \"a\", @progbits;\n\t" \ > + ".long %1, 0f, %2;\n\t" \ > + ".previous;\n\t" \ > + ".align 2\n\t" \ > + "0:\n\t" \ > + "movb %3,%0;\n\t" \ > + : "=r" (condition) \ > + : "m" (*__cstrtab_name_##name), \ > + "m" (*(char*)flags), \ > + "i" ((flags) & CF_STATIC_ENABLE)); \
Remind me what we need the flags again for?
I would prefer to just eliminate them and always require arming.
> + (likely(!condition)) ? \ > + (__typeof__(func))0 : \ > + (func); \ > + }) > + > +/* cond_call macro selecting the generic or optimized version of cond_call, > + * depending on the flags specified. */ > +#define _cond_call(flags, name, func) \ > +({ \ > + (((flags) & CF_LOCKDEP) && ((flags) & CF_OPTIMIZED)) ? \
Similar here? unoptimized condcalls don't make much sense. I also don't understand what the LOCKDEP flag is good for.
> Index: linux-2.6-lttng/arch/i386/kernel/condcall.c > =================================================================== > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > +++ linux-2.6-lttng/arch/i386/kernel/condcall.c 2007-05-17 01:52:38.000000000 -0400 > @@ -0,0 +1,140 @@ > +/* condcall.c > + * > + * - Erratum 49 fix for Intel PIII. > + * - Still present on newer processors : Intel Core 2 Duo Processor for Intel > + * Centrino Duo Processor Technology Specification Update, AH33. > + * Unsynchronized Cross-Modifying Code Operations Can Cause Unexpected > + * Instruction Execution Results.
Can you please define a generic utility function to do self modifying code? There are other places that do it too.
> +static DEFINE_MUTEX(cond_call_mutex);
All locks need a comment describing what they protect and the hierarchy if any.
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