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Re: disabling tls in glibc-2.3.2


On Tue, 21 Mar 2006, Daniel Jacobowitz stipulated:
> On Tue, Mar 21, 2006 at 09:04:27PM +0000, Nix wrote:
>> >                2nd question, if I want to disable tls libraries
>> > globally, how can I change the order of ld cache using ldconfig?  I
>> > only came up with a brute chmod 0 /lib/tls, but there have to be a
>> > better way.
>> 
>> For *every* other hwcap, there is. For TLS, I can't see one.
> 
> Generally you control this using LD_ASSUME_KERNEL.  Things built for
> 2.6.0 or higher will use TLS and otherwise not.  This is just a
> convention among distributors.

Yeah, I remembered that about two seconds after sending the email :/

This has always struck me as relying on a side-effect, though; there are
liable to be other newer things that are disabled by LD_ASSUME_KERNEL,
especially now that glibc-2.4 has acquired the *at() syscalls and so
on. (Admittedly, this is unlikely to be harmful; the occasions on which
one needs to disable TLS searching are dropping by the day --- my last
one just vanished with Blaisorblade's patches to make user-mode-linux
set_thread_area()-capable --- and the *at() functions are mostly useful
in threaded apps. Plus of course, if someone cares about threaded
performance in some app they're not going to be disabling TLS! This
is probably why nobody's added this feature: glibc is feature-laden
enough as it is...)

-- 
`Come now, you should know that whenever you plan the duration of your
 unplanned downtime, you should add in padding for random management
 freakouts.'


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