Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753341AbbGWKxV (ORCPT ); Thu, 23 Jul 2015 06:53:21 -0400 Received: from mail.skyhub.de ([78.46.96.112]:53952 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752737AbbGWKxQ (ORCPT ); Thu, 23 Jul 2015 06:53:16 -0400 Date: Thu, 23 Jul 2015 12:53:09 +0200 From: Borislav Petkov To: Peter Zijlstra Cc: Jason Baron , Andy Lutomirski , Thomas Gleixner , Mikulas Patocka , Paul Mackerras , Arnaldo Carvalho de Melo , Kees Cook , Andrea Arcangeli , Vince Weaver , "hillf.zj" , Valdis Kletnieks , "linux-kernel@vger.kernel.org" , Steven Rostedt Subject: Re: Kernel broken on processors without performance counters Message-ID: <20150723105309.GE18642@nazgul.tnic> References: <20150721082107.GE18673@twins.programming.kicks-ass.net> <20150721154959.GS19282@twins.programming.kicks-ass.net> <20150721161215.GU19282@twins.programming.kicks-ass.net> <20150721181553.GA3378@nazgul.tnic> <55AE9471.1000601@gmail.com> <20150722042403.GA6345@nazgul.tnic> <55AFCDA4.5010406@gmail.com> <20150723104215.GH25159@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150723104215.GH25159@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3441 Lines: 96 On Thu, Jul 23, 2015 at 12:42:15PM +0200, Peter Zijlstra wrote: > > static_likely_init_true_branch(struct static_likely_init_true_key *key) > > static_likely_init_false_branch(struct static_likely_init_false_key *key) > > static_unlikely_init_false_branch(struct static_unlikely_init_false_key *key) > > static_unlikely_init_true_branch(struct static_unlikely_init_true_key *key) > > I'm sorely tempted to go quote cypress hill here... Yah, those are at least too long and nuts. > And I realize part of the problem is that we're wanting to use jump > labels before we can patch them. But surely we can do better. > > extern bool ____wrong_branch_error(void); > > struct static_key_true; > struct static_key_false; > > #define static_branch_likely(x) \ > ({ \ > bool branch; \ > if (__builtin_types_compatible_p(typeof(x), struct static_key_true)) \ > branch = !arch_static_branch(&(x)->key); \ > else if (__builtin_types_compatible_p(typeof(x), struct static_key_false)) \ > branch = !arch_static_branch_jump(&(x)->key); \ > else \ > branch = ____wrong_branch_error(); \ > branch; \ > }) > > #define static_branch_unlikely(x) \ > ({ \ > bool branch; \ > if (__builtin_types_compatible_p(typeof(x), struct static_key_true)) \ > branch = arch_static_branch(&(x)->key); \ > else if (__builtin_types_compatible_p(typeof(x), struct static_key_false)) \ > branch = arch_static_branch_jump(&(x)->key); \ > else \ > branch = ____wrong_branch_error(); \ > branch; \ > }) > > Can't we make something like that work? > > So the immediate problem appears to be the 4 different key inits, which don't > seem very supportive of this separation: > > +#define STATIC_KEY_LIKEY_INIT_TRUE ((struct static_unlikely_init_true_key) \ LIKELY > + { .key.enabled = ATOMIC_INIT(1), \ > + .key.entries = (void *)JUMP_LABEL_TYPE_TRUE_BRANCH }) > > +#define STATIC_KEY_LIKEY_INIT_FALSE ((struct static_unlikely_init_false_key) \ Yuck, those struct names are still too long IMO. > + { .key.enabled = ATOMIC_INIT(0), \ > + .key.entries = (void *)JUMP_LABEL_TYPE_TRUE_BRANCH }) > > +#define STATIC_KEY_UNLIKELY_INIT_TRUE ((struct static_unlikely_init_true_key) \ > + { .key.enabled = ATOMIC_INIT(1), \ > + .key.entries = (void *)JUMP_LABEL_TYPE_FALSE_BRANCH }) > > +#define STATIC_KEY_UNLIKELY_INIT_FALSE ((struct static_unlikely_init_false_key) \ > + { .key.enabled = ATOMIC_INIT(0), \ > + .key.entries = (void *)JUMP_LABEL_TYPE_FALSE_BRANCH }) > > > But I think we can fix that by using a second __jump_table section, then > we can augment the LABEL_TYPE_{TRUE,FALSE} thing with the section we > find the jump_entry in. > > Then we can do: > > #define STATIC_KEY_TRUE_INIT (struct static_key_true) { .key = STATIC_KEY_INIT_TRUE, } > #define STATIC_KEY_FALSE_INIT (struct static_key_false){ .key = STATIC_KEY_INIT_FALSE, } Let's abbreviate that "STATIC_KEY" thing too: SK_TRUE_INIT SK_FALSE_INIT ... -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/