Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753460AbbHCNuI (ORCPT ); Mon, 3 Aug 2015 09:50:08 -0400 Received: from smtprelay.synopsys.com ([198.182.60.111]:59183 "EHLO smtprelay.synopsys.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752621AbbHCNuG convert rfc822-to-8bit (ORCPT ); Mon, 3 Aug 2015 09:50:06 -0400 From: Vineet Gupta To: Peter Zijlstra CC: lkml , "arc-linux-dev@synopsys.com" Subject: Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of failed SCOND with exponential backoff Thread-Topic: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of failed SCOND with exponential backoff Thread-Index: AQHQzeFRjbAtcvqjWUyBSa5w/nnd2g== Date: Mon, 3 Aug 2015 13:50:01 +0000 Message-ID: References: <1438596188-10875-1-git-send-email-vgupta@synopsys.com> <1438596188-10875-6-git-send-email-vgupta@synopsys.com> <20150803114104.GK25159@twins.programming.kicks-ass.net> Accept-Language: en-US, en-IN Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.12.197.191] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7832 Lines: 198 On Monday 03 August 2015 06:31 PM, Vineet Gupta wrote: > On Monday 03 August 2015 05:11 PM, Peter Zijlstra wrote: >> > On Mon, Aug 03, 2015 at 03:33:07PM +0530, Vineet Gupta wrote: >>> >> +#define SCOND_FAIL_RETRY_VAR_DEF \ >>> >> + unsigned int delay = 1, tmp; \ >>> >> + >>> >> +#define SCOND_FAIL_RETRY_ASM \ >>> >> + " bz 4f \n" \ >>> >> + " ; --- scond fail delay --- \n" \ >>> >> + " mov %[tmp], %[delay] \n" /* tmp = delay */ \ >>> >> + "2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \ >>> >> + " sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \ >>> >> + " asl %[delay], %[delay], 1 \n" /* delay *= 2 */ \ >>> >> + " b 1b \n" /* start over */ \ >>> >> + "4: ; --- success --- \n" \ >>> >> + >>> >> +#define SCOND_FAIL_RETRY_VARS \ >>> >> + ,[delay] "+&r" (delay),[tmp] "=&r" (tmp) \ >>> >> + >>> >> +#define ATOMIC_OP(op, c_op, asm_op) \ >>> >> +static inline void atomic_##op(int i, atomic_t *v) \ >>> >> +{ \ >>> >> + unsigned int val, delay = 1, tmp; \ >> > Maybe use your SCOND_FAIL_RETRY_VAR_DEF ? > Right - not sure how I missed that ! > >> > >>> >> + \ >>> >> + __asm__ __volatile__( \ >>> >> + "1: llock %[val], [%[ctr]] \n" \ >>> >> + " " #asm_op " %[val], %[val], %[i] \n" \ >>> >> + " scond %[val], [%[ctr]] \n" \ >>> >> + " \n" \ >>> >> + SCOND_FAIL_RETRY_ASM \ >>> >> + \ >>> >> + : [val] "=&r" (val) /* Early clobber to prevent reg reuse */ \ >>> >> + SCOND_FAIL_RETRY_VARS \ >>> >> + : [ctr] "r" (&v->counter), /* Not "m": llock only supports reg direct addr mode */ \ >>> >> + [i] "ir" (i) \ >>> >> + : "cc"); \ >>> >> +} \ >>> >> + >>> >> +#define ATOMIC_OP_RETURN(op, c_op, asm_op) \ >>> >> +static inline int atomic_##op##_return(int i, atomic_t *v) \ >>> >> +{ \ >>> >> + unsigned int val, delay = 1, tmp; \ >> > Idem. > OK ! > >>> >> + \ >>> >> + /* \ >>> >> + * Explicit full memory barrier needed before/after as \ >>> >> + * LLOCK/SCOND thmeselves don't provide any such semantics \ >>> >> + */ \ >>> >> + smp_mb(); \ >>> >> + \ >>> >> + __asm__ __volatile__( \ >>> >> + "1: llock %[val], [%[ctr]] \n" \ >>> >> + " " #asm_op " %[val], %[val], %[i] \n" \ >>> >> + " scond %[val], [%[ctr]] \n" \ >>> >> + " \n" \ >>> >> + SCOND_FAIL_RETRY_ASM \ >>> >> + \ >>> >> + : [val] "=&r" (val) \ >>> >> + SCOND_FAIL_RETRY_VARS \ >>> >> + : [ctr] "r" (&v->counter), \ >>> >> + [i] "ir" (i) \ >>> >> + : "cc"); \ >>> >> + \ >>> >> + smp_mb(); \ >>> >> + \ >>> >> + return val; \ >>> >> +} >>> >> +#define SCOND_FAIL_RETRY_VAR_DEF \ >>> >> + unsigned int delay, tmp; \ >>> >> + >>> >> +#define SCOND_FAIL_RETRY_ASM \ >>> >> + " ; --- scond fail delay --- \n" \ >>> >> + " mov %[tmp], %[delay] \n" /* tmp = delay */ \ >>> >> + "2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \ >>> >> + " sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \ >>> >> + " asl %[delay], %[delay], 1 \n" /* delay *= 2 */ \ >>> >> + " b 1b \n" /* start over */ \ >>> >> + " \n" \ >>> >> + "4: ; --- done --- \n" \ >>> >> + >>> >> +#define SCOND_FAIL_RETRY_VARS \ >>> >> + ,[delay] "=&r" (delay), [tmp] "=&r" (tmp) \ >> > This is looking remarkably similar to the previous ones, why not a >> > shared header? On second thoughts, the duplication of atomic generator macros seems to be superflous ... Below is much more readable and shorter. ------------> diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h index 3dd36c1efee1..c2e012ca4560 100644 --- a/arch/arc/include/asm/atomic.h +++ b/arch/arc/include/asm/atomic.h @@ -23,17 +23,50 @@ #define atomic_set(v, i) (((v)->counter) = (i)) +#ifdef CONFIG_ARC_STAR_9000923308 + +#define SCOND_FAIL_RETRY_VAR_DEF \ + unsigned int delay = 1, tmp; \ + +#define SCOND_FAIL_RETRY_ASM \ + " bz 4f \n" \ + " ; --- scond fail delay --- \n" \ + " mov %[tmp], %[delay] \n" /* tmp = delay */ \ + "2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \ + " sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \ + " asl %[delay], %[delay], 1 \n" /* delay *= 2 */ \ + " b 1b \n" /* start over */ \ + "4: ; --- success --- \n" \ + +#define SCOND_FAIL_RETRY_VARS \ + ,[delay] "+&r" (delay),[tmp] "=&r" (tmp) \ + +#else /* !CONFIG_ARC_STAR_9000923308 */ + +#define SCOND_FAIL_RETRY_VAR_DEF + +#define SCOND_FAIL_RETRY_ASM \ + " bnz 1b \n" \ + +#define SCOND_FAIL_RETRY_VARS + +#endif + #define ATOMIC_OP(op, c_op, asm_op) \ static inline void atomic_##op(int i, atomic_t *v) \ { \ - unsigned int val; \ + unsigned int val; \ + SCOND_FAIL_RETRY_VAR_DEF \ \ __asm__ __volatile__( \ "1: llock %[val], [%[ctr]] \n" \ " " #asm_op " %[val], %[val], %[i] \n" \ " scond %[val], [%[ctr]] \n" \ - " bnz 1b \n" \ + " \n" \ + SCOND_FAIL_RETRY_ASM \ + \ : [val] "=&r" (val) /* Early clobber to prevent reg reuse */ \ + SCOND_FAIL_RETRY_VARS \ : [ctr] "r" (&v->counter), /* Not "m": llock only supports reg direct addr mode */ \ [i] "ir" (i) \ : "cc"); \ @@ -42,7 +75,8 @@ static inline void atomic_##op(int i, atomic_t *v) \ #define ATOMIC_OP_RETURN(op, c_op, asm_op) \ static inline int atomic_##op##_return(int i, atomic_t *v) \ { \ - unsigned int val; \ + unsigned int val; \ + SCOND_FAIL_RETRY_VAR_DEF \ \ /* \ * Explicit full memory barrier needed before/after as \ @@ -54,8 +88,11 @@ static inline int atomic_##op##_return(int i, atomic_t *v) \ "1: llock %[val], [%[ctr]] \n" \ " " #asm_op " %[val], %[val], %[i] \n" \ " scond %[val], [%[ctr]] \n" \ - " bnz 1b \n" \ + " \n" \ + SCOND_FAIL_RETRY_ASM \ + \ : [val] "=&r" (val) \ + SCOND_FAIL_RETRY_VARS \ : [ctr] "r" (&v->counter), \ [i] "ir" (i) \ : "cc"); \ @@ -142,6 +179,9 @@ ATOMIC_OP(and, &=, and) #undef ATOMIC_OPS #undef ATOMIC_OP_RETURN #undef ATOMIC_OP +#undef SCOND_FAIL_RETRY_VAR_DEF +#undef SCOND_FAIL_RETRY_ASM +#undef SCOND_FAIL_RETRY_VARS /** * __atomic_add_unless - add unless the number is a given value -- 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/