summaryrefslogtreecommitdiff
path: root/open_issues/libpthread_addon.mdwn
blob: 3a10cbdea287333acc2fb914b603a3efc6ed40b1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
[[!meta copyright="Copyright © 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
document under the terms of the GNU Free Documentation License, Version 1.2 or
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
License|/fdl]]."]]"""]]

[[!meta title="libpthread as glibc addon"]]

[[!tag open_issue_glibc open_issue_libpthread]]

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: [[hurd/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.