Re: qemu couldn't connect the unix domain socket

[Stefano Brivio <sbrivio@redhat.com>]

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Hello again,

On Fri, 29 Oct 2021 13:52:31 +0200
Stefano Brivio <sbrivio(a)redhat.com> wrote:

> On Fri, 29 Oct 2021 19:02:15 +0800
> Li Feng <fengli(a)smartx.com> wrote:
> > 
> > [...]
> >
> > clone(child_stack=NULL,
> > flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLDstrace: Process
> > 172939 attached
> > , child_tidptr=0x7f7b89b1da10) = 172939
> > [pid 172921] exit_group(0 <unfinished ...>
> > [pid 172939] set_robust_list(0x7f7b89b1da20, 24 <unfinished ...>
> > [pid 172921] <... exit_group resumed>)  = ?
> > [pid 172921] +++ exited with 0 +++
> > <... set_robust_list resumed>)          = ?
> > +++ killed by SIGSYS (core dumped) +++
> > ```
> > Which is the bad syscall?  
> 
> Oh, it's set_robust_list(), it's normal that exit_group() doesn't
> return. That new usage probably comes from:
> 	https://sourceware.org/git/?p=glibc.git;a=commit;h=9a7565403758f65c07fe3705e966381d9cfd35b6
> 
> and that code path is not really needed for passt, so I would have a
> quick try at avoiding it rather than adding a syscall, perhaps with a
> small replacement of daemon() using clone() instead of fork().

I forgot to follow up here: in the end I pushed a change that, among
other calls, allows set_robust_list() unconditionally:
	https://passt.top/passt/commit/?id=33b1bdd079f1b40dffb040e40579d7434c28d10a

alternatives looked quite awkward, a replacement of daemon() also
didn't look very small, other suggestions warmly welcome.

By the way, the new tests checking build and basic functionality also
cover Fedora 35.

-- 
Stefano