Re: EINTR in ftruncate()

Hi,

On 2022-07-04 13:07:50 +0200, Alvaro Herrera wrote:
> On 2022-Jul-01, Andres Freund wrote:
>
> > On 2022-07-01 19:55:16 +0200, Alvaro Herrera wrote:
> > > On 2022-Jul-01, Andres Freund wrote:
>
> > > > What is the reason for the || ProcDiePending || QueryCancelPending bit? What
> > > > if there's dsm operations intentionally done while QueryCancelPending?
> > >
> > > That mirrors the test for the other block in that function, which was
> > > added by 63efab4ca139, whose commit message explains:
>
> > That whole approach seems quite wrong to me. At the absolute very least the
> > code needs to check if interrupts are being processed in the current context
> > before just giving up due to ProcDiePending || QueryCancelPending.
>
> For the time being, I can just push the addition of the EINTR retry
> without testing ProcDiePending || QueryCancelPending.

I think we'd be better off disabling at least some signals during
dsm_impl_posix_resize(). I'm afraid we'll otherwise just find another
variation of these problems. I haven't checked the source of ftruncate, but
what Thomas dug up for fallocate makes it pretty clear that our current
approach of just retrying again and again isn't good enough. It's a bit more
obvious that it's a problem for fallocate, but I don't think it's worth having
different solutions for the two.

Greetings,

Andres Freund