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[[!meta copyright="Copyright © 2011, 2012, 2013 Free Software Foundation,
Inc."]]
[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
id="license" text="Permission is granted to copy, distribute and/or modify this
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any later version published by the Free Software Foundation; with no Invariant
Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
is included in the section entitled [[GNU Free Documentation
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[[!tag open_issue_glibc open_issue_libpthread]]
This basically means to get rid of `sysdeps/mach/hurd/bits/libc-tsd.h` (and
thus the `_HURD_THREADVAR_*`/`_hurd_threadvar_location` interface), and
directly use `__thread` instead.
[[!toc]]
# IRC, freenode, #hurd, 2011-10-23
<tschwinge> youpi: If we want to replace threadvars with TLS, there is one
problem: the threadvars interface is publically exported:
/usr/include/hurd/threadvar.h.
<tschwinge> youpi: But I am somewhat inclined to say that the only user of
this is libthreads/libpthread. Do you think differently?
<youpi> tschwinge: that's very probable
<youpi> so I think we can just drop it
<youpi> (people should use TLS anyway)
[[libpthread_set_stack_size]].
After this has been done, probably the whole `__libc_tsd_*` stuff can be
dropped altogether, and `__thread` directly be used in glibc.
# IRC, freenode, #hurd, 2012-08-07
<tschwinge> r5219: Update libpthread patch to replace threadvar with tls
for pthread_self
<tschwinge> r5224: revert r5219 too, it's not ready either
<youpi> as the changelog says, the __thread revertal is because it posed
problems
<youpi> and I just didn't have any time to check them while the freeze was
so close
<tschwinge> OK. What kind of problems? Should it be reverted upstream,
too?
<youpi> I don't remember exactly
<youpi> it should just be fixed
<youpi> we can revert it upstream, but it'd be good that we manage to
progress, at some point...
<tschwinge> Of course -- however as long as we don't know what kind of
problem, it is a bit difficult. ;-)
<youpi> since I didn't left a note, it was most probably a mere glibc run,
or boot with the patched libpthread
<youpi> *testsuite run
<tschwinge> OK.
<tschwinge> The libpthread testsuite doesn't show any issues with that
patch applied, though. But I didn'T test anything else.
<tschwinge> youpi: Also, you have probably seen my glibc __thread errno
email -- rmcgrath wanted to find some time this week to comment/help, and
I take it you don't have any immediate comments to that issue?
<youpi> I saw the mails, but didn't investigate at all
[[!message-id "878vdyqht3.fsf@kepler.schwinge.homeip.net"]].
# `getcontext`/`setcontext`
Needed for [[gccgo]].
Instead of adding support for `getcontext`/`setcontext` within the Hurd
threadvar context, which might become a bit ugly, the idea is to get rid of
Hurd threadvars and replace them with TLS (as we want to, anyway).
## IRC, freenode, #hurd, 2012-04-19
<gnu_srs> How much work/knowledge is needed to implement
getcontext/setcontext?
<gnu_srs> Any already implemented alternatives available?
<youpi> x86 registers knowledge, as well as unix signal masks
<youpi> there's the linux implementation that can be taken as an
exxample, but the signal part has to be rewritten
<gnu_srs> Well, it's a pity they are not implemented. That's the
remaining hurdle to get gccgo working :-(
<youpi> uh :/
<gnu_srs> Everything builds, but the testsuite fails due to these
missing functions.
<gnu_srs> Regarding getcontext/setcontext they seem to be written
in assembly for linux but the code is not very long.
<gnu_srs> How much effort would it be to write something similar
for Hurd? Anybody fluent in asm?
<gnu_srs> And registers and signals.
<tschwinge> gnu_srs: Signals is the key thing -- everything else we
can probably just copy. I have never/not yet looked at it,
though.
<gnu_srs> For kfreebsd it is written in C: kern_context.c, 3/4 in
one file: getcontext, setcontext, swapcontext, not makecontext.
<gnu_srs> Dunno how much assembly calls used though.
<gnu_srs> Hi, any preferences about implementing get/setcontext in
C or Asm?
<tschwinge> gnu_srs: I think these will have to be implemented in
assembly. Based on the Linux x86 variants.
### IRC, freenode, #hurd, 2012-04-20
<tschwinge> youpi: Your understanding of that is better than mine
-- the *context stuff can't be very useful at the moment, because
when the user changes uc_stack.ss_sp (which the glibc tests are
doing), we're losing access to the _hurd_threadvars. Correct?
<tschwinge> At least the getcontext test works, the other get a
SIGILL.
<tschwinge> others
<tschwinge> _hurd_threadvars issue is just guessing.
<youpi> tschwinge: yes, threadvars are on the stack
<youpi> threadvars is not much code, it should just work, but care
has to be taken on the libpthread/libthread side, which does some
initialization
<tschwinge> OK, that at least matches my understanding.
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