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Re: extending wait4(2) or waitid(2) linux syscall
- From: Arnd Bergmann <arnd at arndb dot de>
- To: "Dmitry V. Levin" <ldv at altlinux dot org>
- Cc: Albert ARIBAUD <albert dot aribaud at 3adev dot fr>, "H. Peter Anvin" <hpa at zytor dot com>, GNU C Library <libc-alpha at sourceware dot org>, Linux API <linux-api at vger dot kernel dot org>
- Date: Fri, 16 Nov 2018 17:50:14 -0800
- Subject: Re: extending wait4(2) or waitid(2) linux syscall
- References: <email@example.com> <20181115140441.GA2171@altlinux.org> <CAK8P3a0Gsqa8WTbALOUchRyEA7E2f3P1f=XQ8nD2xQaemfPpcQ@mail.gmail.com> <20181115153008.GC2171@altlinux.org>
On Thu, Nov 15, 2018 at 7:30 AM Dmitry V. Levin <firstname.lastname@example.org> wrote:
> On Thu, Nov 15, 2018 at 06:39:03AM -0800, Arnd Bergmann wrote:
> > On Thu, Nov 15, 2018 at 6:05 AM Dmitry V. Levin wrote:
> > > On Thu, Apr 20, 2017 at 03:20:51PM +0200, Albert ARIBAUD wrote:
> 1. strace needs a race-free invocation of wait4(2) or waitid(2)
> with a different signal mask, this cannot be achieved without
> an extended version of syscall, similar to pselect6(2) extension
> over select(2) and ppoll(2) extension over poll(2).
> Signal mask specification in linux requires two parameters:
> "const sigset_t *sigmask" and "size_t sigsetsize".
> Creating pwait6(2) as an extension of wait4(2) with two arguments
> is straightforward.
> Creating pwaitid(2) as an extension of waitid(2) that already has 5
> arguments would require an indirection similar to pselect6(2).
Getting back to this point: you could also do the same thing with
the CLONE_FD approach from Josh Triplett or Casey Dahlin's
older waitfd() syscall, correct?
Neither of them got merged, bu t we could revisit the ideas if they
make it easier to solve your problem by calling ppoll().