Re: Control Dependencies vs C Compilers

Paul E. McKenney
2020-10-06T16:31:44Z

On Tue, Oct 06, 2020 at 04:22:10PM +0000, David Laight wrote:
> From: Willy Tarreau
> > Sent: 06 October 2020 17:11
> >
> > On Tue, Oct 06, 2020 at 08:50:52AM -0700, Paul E. McKenney wrote:
> > > Comparing 25+ assembly languages to but two compilers most definitely
> > > motivates looking hard at doing something with the compilers.
> >
> > +1, especially since the kernel is not special; anyone working with
> > threads faces the same issues in userland, which are often hidden
> > behind the implicit whole-memory clobbers of certain operations or
> > the call to mutex manipulation functions, but which become a reality
> > again as soon as you go slightly away from these and try to use
> > lockless mechanisms.
>
> AFAICT most windows and android apps completely ignore the problem
> of thread locking - which is why the crash and lock up all the time :-)
>
> I've spent most of the day looking at some library traces from a
> customer bug.
> I almost suspect a bug in the pthread mutex code on their system.
> They are using a nice, modern, 3.10.0-957.el7.x86_64 kernel.

It would be good if the compiler were more helpful! Failing that, if
-something- could be more helpful!!!

Thanx, Paul