Blackfin Buildroot toolchain issue

Dear Gustavo Zacarias,

On Tue, 17 Mar 2015 12:08:16 -0300, Gustavo Zacarias wrote:

> There's this as well:
> https://bugs.busybox.net/show_bug.cgi?id=7921
> Which basically boils down to uclibc NPTL requiring TLS.
> I'll check for space savings to see if it makes sense for it to even be
> an option.

I think it might make sense to keep it a blind option so that we don't
do --enable-tls on architectures that don't have TLS support at all (if
that even exists).

I have something like that in one of my branches:

commit 2ea50f3887747d6b72d6b133806d8b3ff995fe4a
Author: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Date:   Wed Mar 11 23:05:00 2015 +0100

    gcc: make TLS option a blind option
    
    The current BR2_GCC_ENABLE_TLS option can lead users to create a
    non-working configuration: if they choose uClibc with NPTL and disable
    TLS support. This is bug #7921.
    
    Since TLS support is really an internal thing, it doesn't make a lot
    of sense to have a visible option for this. Therefore, this commit
    turns it to a blind option: TLS support is enabled in the compiler if
    glibc, eglibc or uClibc NPTL are used, and is disabled otherwise.
    
    Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>



Thomas

On 03/17/2015 12:13 PM, Thomas Petazzoni wrote:

> Dear Gustavo Zacarias,
> 
> On Tue, 17 Mar 2015 12:08:16 -0300, Gustavo Zacarias wrote:
> 
>> There's this as well:
>> https://bugs.busybox.net/show_bug.cgi?id=7921
>> Which basically boils down to uclibc NPTL requiring TLS.
>> I'll check for space savings to see if it makes sense for it to even be
>> an option.
> 
> I think it might make sense to keep it a blind option so that we don't
> do --enable-tls on architectures that don't have TLS support at all (if
> that even exists).

If blackfin supports it, everyone does ;)

>  config BR2_GCC_ENABLE_TLS
> -       bool "Enable compiler tls support" if BR2_TOOLCHAIN_BUILDROOT_UCLIBC
> +       bool
>         default y
>         depends on BR2_PTHREADS_NATIVE || BR2_TOOLCHAIN_BUILDROOT_EGLIBC || BR2_TOOLCHAIN_BUILDROOT_GLIBC
> -       help
> -         Enable the compiler to generate code for accessing
> -         thread local storage variables

Makes sense, the previous conditions were flawed as blackfin showed us,
no nptl but tls was there just fine.
Regards.

Hi,
Gustavo Zacarias wrote,

> On 03/17/2015 12:13 PM, Thomas Petazzoni wrote:
> 
> > Dear Gustavo Zacarias,
> > 
> > On Tue, 17 Mar 2015 12:08:16 -0300, Gustavo Zacarias wrote:
> > 
> >> There's this as well:
> >> https://bugs.busybox.net/show_bug.cgi?id=7921
> >> Which basically boils down to uclibc NPTL requiring TLS.
> >> I'll check for space savings to see if it makes sense for it to even be
> >> an option.
> > 
> > I think it might make sense to keep it a blind option so that we don't
> > do --enable-tls on architectures that don't have TLS support at all (if
> > that even exists).
> 
> If blackfin supports it, everyone does ;)

My opinion on this is, that there are systems supporting threads
with uClibc, which do not have TLS support. Linuxthreads.old does
not make use of TLS. When you build for coldfire or ARM noMMU, tls 
is not available and it should be disabled while configuring gcc.

I am wondering why Blackfin enables TLS without any NPTL support.

best regards
 Waldemar

Dear Waldemar Brodkorb,

On Tue, 17 Mar 2015 22:34:03 +0100, Waldemar Brodkorb wrote:

> My opinion on this is, that there are systems supporting threads
> with uClibc, which do not have TLS support. Linuxthreads.old does
> not make use of TLS. When you build for coldfire or ARM noMMU, tls 
> is not available and it should be disabled while configuring gcc.

Sure, but we don't have to make this an option. The plan is to enable
TLS only when available.

Best regards,

Thomas

Hi,
Thomas Petazzoni wrote,

> Dear Waldemar Brodkorb,
> 
> On Tue, 17 Mar 2015 22:34:03 +0100, Waldemar Brodkorb wrote:
> 
> > My opinion on this is, that there are systems supporting threads
> > with uClibc, which do not have TLS support. Linuxthreads.old does
> > not make use of TLS. When you build for coldfire or ARM noMMU, tls 
> > is not available and it should be disabled while configuring gcc.
> 
> Sure, but we don't have to make this an option. The plan is to enable
> TLS only when available.

Yeah, that would be very good.

best regards
 Waldemar