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Re: [PATCH][BZ 18743] PowerPC: Fix a race condition when eliding a lock
- From: Torvald Riegel <triegel at redhat dot com>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: Tulio Magno Quites Machado Filho <tuliom at linux dot vnet dot ibm dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Mon, 03 Aug 2015 18:25:55 +0200
- Subject: Re: [PATCH][BZ 18743] PowerPC: Fix a race condition when eliding a lock
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- References: <1438274936-26493-1-git-send-email-tuliom at linux dot vnet dot ibm dot com> <55BA703D dot 7010303 at linaro dot org> <874mkl3wtq dot fsf at totoro dot lan> <55BB76FA dot 5040703 at linaro dot org> <87zj2c1ij1 dot fsf at totoro dot lan> <55BBD3E9 dot 8040005 at linaro dot org> <87oaisxaqu dot fsf at totoro dot lan> <55BBEFC5 dot 8070105 at linaro dot org> <87a8ucx6zy dot fsf at totoro dot lan> <62B20246-954F-4B5F-89B4-EF073DA4D02A at linaro dot org>
On Sat, 2015-08-01 at 09:23 -0300, Adhemerval Zanella wrote:
>
>
>
> > Em 31/07/2015, Ãs 20:05, Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com> escreveu:
> >
> > Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:
> >
> >> Mainly because I see this issue is not powerpc specific and I think we should
> >> also fix for x86 (that currently also uses the same mechanism) and for future
> >> arches that also might potentially implement lock elision using this.
> >
> > AFAICS, this is powerpc specific. x86 ensures the memory access happens
> > inside the transaction.
> >
> > Here is the x86 implementation:
> >
>
> Right, x86 is evaluated as a macro. Indeed your initial approach seems to be better indeed. Thanks for catching it. I would suggest add a comment similar to x86 as well.
>
> > 50 /* is_lock_free must be executed inside the transaction */
> > 51
I think "evaluated" is better in this case.