Re: [PATCH 18/20] Fix elf/tst-dlmopen-twice to support enough link namespaces

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 10/27/2022 18:24, Florian Weimer wrote:
> * Szabolcs Nagy via Libc-alpha:
> 
> > The test dlmopens 10 namespaces recursively, which requires a glibc
> > tunable setting, otherwise it may run out of static TLS.
> > ---
> >  elf/Makefile            | 1 +
> >  elf/tst-dlmopen-twice.c | 2 +-
> >  2 files changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/elf/Makefile b/elf/Makefile
> > index 7b50ccc07a..ace15dc11b 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -2969,6 +2969,7 @@ tst-audit-tlsdesc-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc.so
> >  $(objpfx)tst-audit-tlsdesc-dlopen.out: $(objpfx)tst-auditmod-tlsdesc.so
> >  tst-audit-tlsdesc-dlopen-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc.so
> >  
> > +tst-dlmopen-twice-ENV = GLIBC_TUNABLES=glibc.rtld.nns=10
> >  $(objpfx)tst-dlmopen-twice.out: \
> >    $(objpfx)tst-dlmopen-twice-mod1.so \
> >    $(objpfx)tst-dlmopen-twice-mod2.so
> > diff --git a/elf/tst-dlmopen-twice.c b/elf/tst-dlmopen-twice.c
> > index 70c71fe19c..dfa58b1505 100644
> > --- a/elf/tst-dlmopen-twice.c
> > +++ b/elf/tst-dlmopen-twice.c
> > @@ -46,7 +46,7 @@ do_test (void)
> >    recurse (1);
> >  
> >    /* Then with nesting.  The constant needs to be less than the
> > -     internal DL_NNS namespace constant.  */
> > +     glibc.rtld.nns tunable (which is between 1 and DL_NNS).  */
> >    recurse (10);
> >    return 0;
> >  }
> 
> This doesn't work if configured with --disable-tunables.
> 
> I suspect this is merely a symptom.  The static TLS sizing defaults
> should allow creating DL_NNS namespaces?

the tunable defaults to 4, DL_NNS is 16 and that's the max value
of the tunable (since that's the static namespace array size)