Messages in this thread | | | Date | Sat, 12 Mar 2016 18:08:56 +0100 | From | Ingo Molnar <> | Subject | Re: [musl] Re: [RFC PATCH] x86/vdso/32: Add AT_SYSINFO cancellation helpers |
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(Argh: Mail-Followup-To spam your mailer sets up is nasty!)
* Szabolcs Nagy <nsz@port70.net> wrote:
> > 4. A calls cancellation point and syscall correctly executes > > 5. Once A enables cancellation again, the cancellation propagates. > > > > So I still see no problem. > > i think the sticky signal design would work, but more > complex than what we have and adds some atomic rmw ops > into common code paths and not backward compatible.
Agreed about complexity, but note that the RMW ops shouldn't really be expensive here, as this should be a well-cached flag. Especially compared to:
> not using vsyscalls for cancellation-points sounds easier.
... FYI not using vsyscalls has _far_ higher cost than using well-cached RMW ops.
So ... what do you think about Linus's SA_SYNCHRONOUS approach? I think it can be made to work without much fuss.
There will still be different code paths on old and new kernels, but that's unavoidable.
Thanks,
Ingo
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