Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch

Nicolas Pitre wrote:

On Tue, 20 Dec 2005, Linus Torvalds wrote:

IOW, why don't you just do

	ldr  lr,[%0]
	subs lr, lr, %1
	str  lr,[%0]
	blmi failure

as the _base_ timings, since that should be the common case. That's the drop-dead fastest UP case.

The above is 5 cycles. About the same as the preemption-safe swp-based mutex implementation on non-Intel ARM. It is broken wrt interrupts when the swp is not.

How it is broken WRT interrupts? (sorry, I haven't had it explained to me
in words of two syllables or less)

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---

• References:
  • [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Ingo Molnar <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Zwane Mwaikambo <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: David Woodhouse <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Ingo Molnar <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Nicolas Pitre <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Nick Piggin <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Nicolas Pitre <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Nick Piggin <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Nicolas Pitre <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Linus Torvalds <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Russell King <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Linus Torvalds <[email protected]>
  • Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch
    • From: Nicolas Pitre <[email protected]>

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