[CinCV TNG] lock problems with suse/leap, which can cause segvs in 5.1

Good Guy good1.2guy at gmail.com
Mon Nov 7 01:38:59 CET 2016


This is from lists.cinelerra

https://mail.google.com/mail/u/0/?tab=wm#search/elision/1557edb707ade7f3

There were mods added which prevent unlocking unlocked a mutex at the time
it was discovered.

If you ever do find direct evidence that there is a problem in cinelerra
mutex use, Please report it.

gg


On Sun, Nov 6, 2016 at 3:58 PM, Petter Reinholdtsen <pere at hungry.com> wrote:

> [Good Guy]
> > As it turns out, intel's lock elision code was causing SEGVs when
> > attempting to unlock a locked mutex.  Since intel seems to be now
> > disavowing TSX locks in the microcode updates,
>
> I believe this is a misunderstanding.  Intel have disabled TSX locks on
> some CPU models where it was broken, but the feature is enabled and used
> on other and more recent CPU models.  Where the feature is disabled,
> using TSX style locks causes SIGILL instead of SIGSEGV.
>
> I've been told that on s390, s390x, Hurd and kFreeBSD, unlocking an
> non-locked mutex will also cause a crash.
>
> > I am not sure that this is not a really issue, unless you have real
> > evidence that there is a problem.
>
> I have not tested if the issue exist in cinelerra.  I know incorrect
> handling of mutexes exist elsewhere, which will cause a segfault on CPUs
> with working TSX.
>
> > Have you run 'valgrind --tool=helgrind' and actually seen problems??
>
> Only with ogg123 so far, which is one of the packages I maintain in
> Debian and which caused the start of the thread on debian-devel that I
> pointed to in my previous message.
>
> --
> Happy hacking
> Petter Reinholdtsen
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