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Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of failed SCOND with exponential backoff

From Vineet Gupta <Vineet.Gupta1@synopsys.com>
Newsgroups linux.kernel
Subject Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of failed SCOND with exponential backoff
Date 2015-08-03 15:10 +0200
Message-ID <pTnF8-3WH-11@gated-at.bofh.it> (permalink)
References <pTkQW-8kh-1@gated-at.bofh.it> <pTkQW-8kh-7@gated-at.bofh.it> <pTmzo-29E-17@gated-at.bofh.it>
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On Monday 03 August 2015 05:21 PM, Peter Zijlstra wrote:

On Mon, Aug 03, 2015 at 03:33:07PM +0530, Vineet Gupta wrote:


> +#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"                             \


One more note, you might want a test to handle the case where delay *= 2
overflows and results in a 0.


yeah !

- asl %[delay], %[delay], 1
+ asl.f  %[delay], %[delay], 1
+ mov.z %[delay], 1


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Thread

[PATCH 0/6] ARC: spinlocks/atomics rework Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 12:10 +0200
  [PATCH 4/6] ARC: LLOCK/SCOND based rwlock Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 12:10 +0200
    Re: [PATCH 4/6] ARC: LLOCK/SCOND based rwlock Peter Zijlstra <peterz@infradead.org> - 2015-08-03 13:40 +0200
      Re: [PATCH 4/6] ARC: LLOCK/SCOND based rwlock Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 14:00 +0200
  [PATCH 6/6] ARCv2: spinlock/rwlock: Reset retry delay when starting a new spin-wait cycle Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 12:10 +0200
    Re: [PATCH 6/6] ARCv2: spinlock/rwlock: Reset retry delay when  starting a new spin-wait cycle Peter Zijlstra <peterz@infradead.org> - 2015-08-03 13:50 +0200
      Re: [PATCH 6/6] ARCv2: spinlock/rwlock: Reset retry delay when  starting a new spin-wait cycle Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 16:50 +0200
        Re: [PATCH 6/6] ARCv2: spinlock/rwlock: Reset retry delay when  starting a new spin-wait cycle Peter Zijlstra <peterz@infradead.org> - 2015-08-03 16:50 +0200
  [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of failed SCOND with exponential backoff Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 12:10 +0200
    Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of  failed SCOND with exponential backoff Peter Zijlstra <peterz@infradead.org> - 2015-08-03 13:50 +0200
      Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of  failed SCOND with exponential backoff Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 15:10 +0200
        Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of  failed SCOND with exponential backoff Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 16:00 +0200
          Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of  failed SCOND with exponential backoff Peter Zijlstra <peterz@infradead.org> - 2015-08-03 16:10 +0200
    Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of  failed SCOND with exponential backoff Peter Zijlstra <peterz@infradead.org> - 2015-08-03 14:00 +0200
      Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of  failed SCOND with exponential backoff Peter Zijlstra <peterz@infradead.org> - 2015-08-03 15:10 +0200
      Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of  failed SCOND with exponential backoff Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 15:10 +0200
  [PATCH 3/6] ARC: LLOCK/SCOND based spin_lock Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 12:10 +0200
    Re: [PATCH 3/6] ARC: LLOCK/SCOND based spin_lock Peter Zijlstra <peterz@infradead.org> - 2015-08-03 13:30 +0200
      Re: [PATCH 3/6] ARC: LLOCK/SCOND based spin_lock Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 13:50 +0200
  [PATCH 1/6] Revert "ARCv2: STAR 9000837815 workaround hardware exclusive transactions livelock" Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 12:10 +0200
  [PATCH 2/6] ARC: refactor atomic inline asm operands with symbolic names Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-08-03 12:10 +0200

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