Re: [PATCH] linux-user: Don't assume 0 is not a valid host timer_t value

[Jon Alduan <jon.alduan@gmail.com>]

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Hello Peter,

I can say so far, your patch solved the issue! Great thanks for that!

Regarding the libc version:
From my WSL2 Ubuntu 21.04 x86_64:
$ ls -l /lib32/libc*
-rwxr-xr-x 1 root root 2042632 Mar 31  2021 /lib32/libc-2.33.so

My gcc version 10 does use the same libc version.
As already mentioned, I can also reproduce this on a VM with Ubuntu 20.04
and libc-2.31.
In addition, originally, this issue was first reproduced with an own
buildroot RootFS and containing libc-2.28.

As you see, the libcs are not that old. What about the virtual environment?
I could not check this hypothesis, but I hope to do so soon.

Thank you again and best regards
Jon

El lun, 25 jul 2022 a las 14:45, Peter Maydell (<peter.maydell@linaro.org>)
escribió:

> On Mon, 25 Jul 2022 at 12:13, Daniel P. Berrangé <berrange@redhat.com>
> wrote:
> >
> > On Mon, Jul 25, 2022 at 12:00:35PM +0100, Peter Maydell wrote:
> > > For handling guest POSIX timers, we currently use an array
> > > g_posix_timers[], whose entries are a host timer_t value, or 0 for
> > > "this slot is unused".  When the guest calls the timer_create syscall
> > > we look through the array for a slot containing 0, and use that for
> > > the new timer.
> > >
> > > This scheme assumes that host timer_t values can never be zero.  This
> > > is unfortunately not a valid assumption -- for some host libc
> > > versions, timer_t values are simply indexes starting at 0.  When
> > > using this kind of host libc, the effect is that the first and second
> > > timers end up sharing a slot, and so when the guest tries to operate
> > > on the first timer it changes the second timer instead.
> >
> > For sake of historical record, could you mention here which specific
> > libc impl / version highlights the problem.
>
> Jon, which host libc are you seeing this with?
>
> thanks
> -- PMM
>


-- 
j.A

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