Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752210Ab3IJVZ0 (ORCPT ); Tue, 10 Sep 2013 17:25:26 -0400 Received: from merlin.infradead.org ([205.233.59.134]:57183 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750844Ab3IJVZX (ORCPT ); Tue, 10 Sep 2013 17:25:23 -0400 Date: Tue, 10 Sep 2013 23:25:09 +0200 From: Peter Zijlstra To: Linus Torvalds Cc: Ingo Molnar , Andi Kleen , Peter Anvin , Mike Galbraith , Thomas Gleixner , Arjan van de Ven , Frederic Weisbecker , Linux Kernel Mailing List , "linux-arch@vger.kernel.org" Subject: Re: [PATCH 0/7] preempt_count rework -v2 Message-ID: <20130910212509.GA18147@laptop.programming.kicks-ass.net> References: <20130910130811.507933095@infradead.org> <20130910135152.GD7537@gmail.com> <20130910135636.GA8268@gmail.com> <20130910164519.GL31370@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9612 Lines: 365 On Tue, Sep 10, 2013 at 10:06:44AM -0700, Linus Torvalds wrote: > > Which is indeed perfect. So should I go 'fix' the other _and_test() > > functions we have to do this same thing? > > It would be a good thing to test. There might be downsides with "asm > goto" (maybe it limits gcc some way), but it does in general save us > not only two instructions but also a register. Here's one that builds and boots on kvm until wanting to mount root. I'm not entirely sure on the "ir" vs "er" thing and atomic64_t and local_t are inconsistent wrt that so I'm too. I'll try running on actual hardware tomorrow sometime. --- arch/x86/include/asm/atomic.h | 52 +++++++++++++++++++++++++++++++++++ arch/x86/include/asm/atomic64_64.h | 54 ++++++++++++++++++++++++++++++++++++- arch/x86/include/asm/local.h | 52 +++++++++++++++++++++++++++++++++++ 3 files changed, 157 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/atomic.h +++ b/arch/x86/include/asm/atomic.h @@ -74,6 +74,18 @@ static inline void atomic_sub(int i, ato * true if the result is zero, or false for all * other cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic_sub_and_test(int i, atomic_t *v) +{ + asm volatile goto(LOCK_PREFIX "subl %1,%0;" + "je %l[became_zero]" + : : "m" (v->counter), "ir" (i) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int atomic_sub_and_test(int i, atomic_t *v) { unsigned char c; @@ -83,6 +95,7 @@ static inline int atomic_sub_and_test(in : "ir" (i) : "memory"); return c; } +#endif /** * atomic_inc - increment atomic variable @@ -116,6 +129,18 @@ static inline void atomic_dec(atomic_t * * returns true if the result is 0, or false for all other * cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic_dec_and_test(atomic_t *v) +{ + asm volatile goto(LOCK_PREFIX "decl %0;" + "je %l[became_zero]" + : : "m" (v->counter) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int atomic_dec_and_test(atomic_t *v) { unsigned char c; @@ -125,6 +150,7 @@ static inline int atomic_dec_and_test(at : : "memory"); return c != 0; } +#endif /** * atomic_inc_and_test - increment and test @@ -134,6 +160,18 @@ static inline int atomic_dec_and_test(at * and returns true if the result is zero, or false for all * other cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic_inc_and_test(atomic_t *v) +{ + asm volatile goto(LOCK_PREFIX "incl %0;" + "je %l[became_zero]" + : : "m" (v->counter) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int atomic_inc_and_test(atomic_t *v) { unsigned char c; @@ -143,6 +181,7 @@ static inline int atomic_inc_and_test(at : : "memory"); return c != 0; } +#endif /** * atomic_add_negative - add and test if negative @@ -153,6 +192,18 @@ static inline int atomic_inc_and_test(at * if the result is negative, or false when * result is greater than or equal to zero. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic_add_negative(int i, atomic_t *v) +{ + asm volatile goto(LOCK_PREFIX "addl %1,%0;" + "js %l[became_neg]" + : : "m" (v->counter), "ir" (i) + : "memory" : became_neg); + return 0; +became_neg: + return 1; +} +#else static inline int atomic_add_negative(int i, atomic_t *v) { unsigned char c; @@ -162,6 +213,7 @@ static inline int atomic_add_negative(in : "ir" (i) : "memory"); return c; } +#endif /** * atomic_add_return - add integer and return --- a/arch/x86/include/asm/atomic64_64.h +++ b/arch/x86/include/asm/atomic64_64.h @@ -70,6 +70,18 @@ static inline void atomic64_sub(long i, * true if the result is zero, or false for all * other cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic64_sub_and_test(long i, atomic64_t *v) +{ + asm volatile goto(LOCK_PREFIX "subq %1,%0;" + "je %l[became_zero]" + : : "m" (v->counter), "er" (i) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int atomic64_sub_and_test(long i, atomic64_t *v) { unsigned char c; @@ -79,6 +91,7 @@ static inline int atomic64_sub_and_test( : "er" (i), "m" (v->counter) : "memory"); return c; } +#endif /** * atomic64_inc - increment atomic64 variable @@ -114,6 +127,18 @@ static inline void atomic64_dec(atomic64 * returns true if the result is 0, or false for all other * cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic64_dec_and_test(atomic64_t *v) +{ + asm volatile goto(LOCK_PREFIX "decq %0;" + "je %l[became_zero]" + : : "m" (v->counter) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int atomic64_dec_and_test(atomic64_t *v) { unsigned char c; @@ -123,6 +148,7 @@ static inline int atomic64_dec_and_test( : "m" (v->counter) : "memory"); return c != 0; } +#endif /** * atomic64_inc_and_test - increment and test @@ -132,6 +158,18 @@ static inline int atomic64_dec_and_test( * and returns true if the result is zero, or false for all * other cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic64_inc_and_test(atomic64_t *v) +{ + asm volatile goto(LOCK_PREFIX "incq %0;" + "je %l[became_zero]" + : : "m" (v->counter) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int atomic64_inc_and_test(atomic64_t *v) { unsigned char c; @@ -141,6 +179,7 @@ static inline int atomic64_inc_and_test( : "m" (v->counter) : "memory"); return c != 0; } +#endif /** * atomic64_add_negative - add and test if negative @@ -151,6 +190,18 @@ static inline int atomic64_inc_and_test( * if the result is negative, or false when * result is greater than or equal to zero. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int atomic64_add_negative(long i, atomic64_t *v) +{ + asm volatile goto(LOCK_PREFIX "addq %1,%0;" + "js %l[became_neg]" + : : "m" (v->counter), "er" (i) + : "memory" : became_neg); + return 0; +became_neg: + return 1; +} +#else static inline int atomic64_add_negative(long i, atomic64_t *v) { unsigned char c; @@ -160,6 +211,7 @@ static inline int atomic64_add_negative( : "er" (i), "m" (v->counter) : "memory"); return c; } +#endif /** * atomic64_add_return - add and return @@ -219,7 +271,7 @@ static inline int atomic64_add_unless(at /* * atomic64_dec_if_positive - decrement by 1 if old value positive - * @v: pointer of type atomic_t + * @v: pointer of type atomic64_t * * The function returns the old value of *v minus 1, even if * the atomic variable, v, was not decremented. --- a/arch/x86/include/asm/local.h +++ b/arch/x86/include/asm/local.h @@ -50,6 +50,18 @@ static inline void local_sub(long i, loc * true if the result is zero, or false for all * other cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int local_sub_and_test(long i, local_t *l) +{ + asm volatile goto(_ASM_SUB " %1,%0;" + "je %l[became_zero]" + : : "m" (l->a.counter), "ir" (i) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int local_sub_and_test(long i, local_t *l) { unsigned char c; @@ -59,6 +71,7 @@ static inline int local_sub_and_test(lon : "ir" (i) : "memory"); return c; } +#endif /** * local_dec_and_test - decrement and test @@ -68,6 +81,18 @@ static inline int local_sub_and_test(lon * returns true if the result is 0, or false for all other * cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int local_dec_and_test(local_t *l) +{ + asm volatile goto(_ASM_DEC " %0;" + "je %l[became_zero]" + : : "m" (l->a.counter) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int local_dec_and_test(local_t *l) { unsigned char c; @@ -77,6 +102,7 @@ static inline int local_dec_and_test(loc : : "memory"); return c != 0; } +#endif /** * local_inc_and_test - increment and test @@ -86,6 +112,18 @@ static inline int local_dec_and_test(loc * and returns true if the result is zero, or false for all * other cases. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int local_inc_and_test(local_t *l) +{ + asm volatile goto(_ASM_INC " %0;" + "je %l[became_zero]" + : : "m" (l->a.counter) + : "memory" : became_zero); + return 0; +became_zero: + return 1; +} +#else static inline int local_inc_and_test(local_t *l) { unsigned char c; @@ -95,6 +133,7 @@ static inline int local_inc_and_test(loc : : "memory"); return c != 0; } +#endif /** * local_add_negative - add and test if negative @@ -105,6 +144,18 @@ static inline int local_inc_and_test(loc * if the result is negative, or false when * result is greater than or equal to zero. */ +#ifdef CC_HAVE_ASM_GOTO +static inline int local_add_negative(long i, local_t *l) +{ + asm volatile goto(_ASM_ADD " %1,%0;" + "js %l[became_neg]" + : : "m" (l->a.counter), "ir" (i) + : "memory" : became_neg); + return 0; +became_neg: + return 1; +} +#else static inline int local_add_negative(long i, local_t *l) { unsigned char c; @@ -114,6 +165,7 @@ static inline int local_add_negative(lon : "ir" (i) : "memory"); return c; } +#endif /** * local_add_return - add and return -- 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/