[Bug libc/29585] sched_getcpu returns invalid results

["mjbaars1977 at gmail dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29585

--- Comment #10 from Mischa Baars <mjbaars1977 at gmail dot com> ---
(In reply to Florian Weimer from comment #9)
> (In reply to Mischa Baars from comment #8)
> > (In reply to Florian Weimer from comment #7)
> > > You cannot call glibc function after creating a bare thread using clone, you
> > > need to use direct system calls. The bare thread does not have a proper
> > > thread control block set up for glibc.
> > 
> > Ok, no problem. I can use syscalls to retrieve the processor the process is
> > running on, but shouldn't glibc check for the existence of this thread
> > control block and return a -1 when it does not exist instead of a incorrect
> > processor number?
> 
> There is no efficient way to check if the TCB is safe to use from the
> current thread.
> 
> > I think that a small note in the manual page about pthreads vs fork / clone
> > would be in order. For example, if the existence of both pthread_yield and
> > sched_yield makes you think that sched_yield is not specifically intended
> > for use with pthreads, then why would sched_getcpu be?
> 
> sched_getcpu is not related to pthreads any more than the rest of glibc.

But you just told me that the TCB is not bare thread related, so it must be
pthread related. Never mind, I'll just use direct system calls to do the
scheduling.

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