Messages in this thread | | | Date | Wed, 29 Nov 2017 20:58:39 +0100 | From | Peter Zijlstra <> | Subject | Re: Unlock-lock questions and the Linux Kernel Memory Model |
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On Wed, Nov 29, 2017 at 11:04:53AM -0800, Daniel Lustig wrote: > "MP+wmb+xchg-acq" (or some such) > > {} > > P0(int *x, int *y) > { > WRITE_ONCE(*x, 1); > smp_wmb(); > WRITE_ONCE(*y, 1); > } > > P1(int *x, int *y) > { > r1 = atomic_xchg_relaxed(y, 2); > r2 = smp_load_acquire(y);
Oh, I wasn't careful enough reading; these are both y.
And then Alan raises a good point in that RmW have dependencies.
Much tricker than I initially thought.
> r3 = READ_ONCE(*x); > } > > exists (1:r1=1 /\ 1:r2=2 /\ 1:r3=0)
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