GNU Hurd/ open issues/ libpthread as glibc addon

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This page lists all the notes, issues, etc, only about compiling libpthread as addon for glibc, not for general libpthread issues.

Building

To build libpthread as glibc addon, copy libpthread inside the glibc tree, and then tell glibc's configure to use it:

$ cp /path/to/libpthread libpthread
$ ./configure [...] --enable-add-ons=[...],libpthread

Currently, it is build like that in Debian since eglibc 2.13-31.

Issues and notes

bits/ headers not used

Recompiling glibc (e.g. on a Debian system) and running the check-local-headers test, check-local-headers.out shows:

*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/pthread.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/thread-attr.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/mutex-attr.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/mutex.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/condition-attr.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/condition.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/rwlock-attr.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/rwlock.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/barrier-attr.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/barrier.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/thread-specific.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/once.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/cancelation.h
*** $(common-objpfx)elf/tst-thrlock.o: uses /usr/include/i386-gnu/bits/pthread-np.h

This happens because these headers are in the bits/ subdirectory in sysdeps/generic -- a generic sysdep is used only for the top-level sysdeps directory in glibc.

Use of hurd's libihash

libpthread makes use of the ihash hurd library, as also glibc's check-local-headers test shows:

*** $(common-objpfx)libpthread/pt-alloc.o: uses /usr/include/hurd/ihash.h

Possible alternatives: libihash.

Executable stack

Running glibc's check-execstack test gives in check-execstack.out:

$BUILDDIR/libpthread/libpthread.so.phdr: *** executable stack signaled

Extra PLT references

Running glibc's check-localplt test gives in check-localplt.out:

Extra PLT reference: libpthread.so: pthread_detach
Extra PLT reference: libpthread.so: pthread_mutex_lock
Extra PLT reference: libpthread.so: pthread_mutexattr_settype
Extra PLT reference: libpthread.so: pthread_rwlock_rdlock
Extra PLT reference: libpthread.so: _pthread_spin_lock
Extra PLT reference: libpthread.so: pthread_attr_setstacksize
Extra PLT reference: libpthread.so: pthread_attr_getstacksize
Extra PLT reference: libpthread.so: pthread_attr_getstackaddr
Extra PLT reference: libpthread.so: pthread_attr_setstackaddr
Extra PLT reference: libpthread.so: pthread_exit
Extra PLT reference: libpthread.so: pthread_getspecific
Extra PLT reference: libpthread.so: __mutex_lock_solid
Extra PLT reference: libpthread.so: pthread_mutex_unlock
Extra PLT reference: libpthread.so: pthread_setcanceltype
Extra PLT reference: libpthread.so: pthread_key_create
Extra PLT reference: libpthread.so: pthread_cond_wait
Extra PLT reference: libpthread.so: pthread_rwlock_wrlock
Extra PLT reference: libpthread.so: pthread_once
Extra PLT reference: libpthread.so: pthread_cond_broadcast
Extra PLT reference: libpthread.so: pthread_setspecific
Extra PLT reference: libpthread.so: __pthread_get_cleanup_stack
Extra PLT reference: libpthread.so: pthread_rwlock_unlock
Extra PLT reference: libpthread.so: pthread_create
Extra PLT reference: libpthread.so: pthread_mutex_init
Extra PLT reference: libpthread.so: pthread_mutexattr_init
Extra PLT reference: libpthread.so: __mutex_unlock_solid
Extra PLT reference: libpthread.so: pthread_mutexattr_destroy
Extra PLT reference: libpthread.so: pthread_setcancelstate

bits/posix_opt.h

bits/posix_opt.h is the glibc header defining the various supported/unsupported _POSIX_* defines (e.g. _POSIX_THREADS, etc).

Currently, glibc's sysdeps/mach/hurd/bits/posix_opt.h is patched in Debian to add all the defines advertizing thread-related support. An idea to avoid this would be to follow what is done in NPTL, and do the following:

  • in glibc: leave sysdeps/mach/hurd/bits/posix_opt.h with no thread-related macros at all.

  • in libpthread: provide sysdeps/mach/hurd/bits/posix_opt.h which would be a copy of glibc's sysdeps/mach/hurd/bits/posix_opt.h with also the thread macros.

This approach would have the drawback that changes in the glibc header must be mirrored also in the libpthread version, but with the advantage that defines according to supported features in libpthread can be added in libpthread's own version (and glibc would pick it automatically).

Tests

The (few) existing tests are not built (thus neither run) just like other tests in glibc.

gai_misc.h

A pthread version of gai_misc.h must be provided by libpthread (just like NPTL provides one), either in sysdeps/mach/hurd or sysdeps/pthread (better).

Currently, it is provided in glibc itself in Debian.