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
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
|
[[!meta copyright="Copyright © 2010 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]]."]]"""]]
Here's what's to be done for maintaining Boehm GC.
This one does need Hurd-specific configuration.
It is, for example, used by [[/GCC]] (which has its own fork), so any changes
committed upstream should very like also be made there.
# [[General information|/boehm_gc]]
# [[Sources|source_repositories/boehm_gc]]
# Configuration
[[tschwinge]] reviewed its GNU/Hurd port's configuration on 2010-12-08, based
on CVS HEAD sources from 2010-12-02, converted to [[Git, correspondingly
1c2455988a8f59a5f83b986b9156f03be395b3b6|source_repositories/boehm_gc]].
* `configure.ac`
* `PARALLEL_MARK` is not enabled; doesn't make sense so far.
* `*-*-kfreebsd*-gnu` defines `USE_COMPILER_TLS`. What's this, and
why does not other config?
* TODO
[ if test "$enable_gc_debug" = "yes"; then
AC_MSG_WARN("Should define GC_DEBUG and use debug alloc. in clients.")
AC_DEFINE([KEEP_BACK_PTRS], 1,
[Define to save back-pointers in debugging headers.])
keep_back_ptrs=true
AC_DEFINE([DBG_HDRS_ALL], 1,
[Define to force debug headers on all objects.])
case $host in
x86-*-linux* | i586-*-linux* | i686-*-linux* | x86_64-*-linux* )
AC_DEFINE(MAKE_BACK_GRAPH)
AC_MSG_WARN("Client must not use -fomit-frame-pointer.")
AC_DEFINE(SAVE_CALL_COUNT, 8)
;;
AM_CONDITIONAL([KEEP_BACK_PTRS], [test x"$keep_back_ptrs" = xtrue])
* `configure.host`
Nothing.
* `Makefile.am`, `include/include.am`, `cord/cord.am`, `doc/doc.am`,
`tests/tests.am`
Nothing.
* `include/gc_config_macros.h`
Should be OK.
* `include/private/gcconfig.h`
Hairy. But should be OK. Search for *HURD*, compare to *LINUX*,
*I386* case.
See `doc/porting.html` and `doc/README.macros` (and others) for
documentation.
*LINUX* has:
* `#define LINUX_STACKBOTTOM`
Defined instead of `STACKBOTTOM` to have the value read from `/proc/`.
* `#define HEAP_START (ptr_t)0x1000`
May want to define it for us, too?
* `#ifdef USE_I686_PREFETCH`, `USE_3DNOW_PREFETCH` --- [...]
Apparently these are optimization that we also could use. Have a
look at *LINUX* for *X86_64*, which uses `__builtin_prefetch`
(which Linux x86 could use, too?).
* TODO
#if defined(LINUX) && defined(USE_MMAP)
/* The kernel may do a somewhat better job merging mappings etc. */
/* with anonymous mappings. */
# define USE_MMAP_ANON
#endif
* TODO
#if defined(GC_LINUX_THREADS) && defined(REDIRECT_MALLOC)
/* Nptl allocates thread stacks with mmap, which is fine. But it */
/* keeps a cache of thread stacks. Thread stacks contain the */
/* thread control blocks. These in turn contain a pointer to */
/* (sizeof (void *) from the beginning of) the dtv for thread-local */
/* storage, which is calloc allocated. If we don't scan the cached */
/* thread stacks, we appear to lose the dtv. This tends to */
/* result in something that looks like a bogus dtv count, which */
/* tends to result in a memset call on a block that is way too */
/* large. Sometimes we're lucky and the process just dies ... */
/* There seems to be a similar issue with some other memory */
/* allocated by the dynamic loader. */
/* This should be avoidable by either: */
/* - Defining USE_PROC_FOR_LIBRARIES here. */
/* That performs very poorly, precisely because we end up */
/* scanning cached stacks. */
/* - Have calloc look at its callers. */
/* In spite of the fact that it is gross and disgusting. */
/* In fact neither seems to suffice, probably in part because */
/* even with USE_PROC_FOR_LIBRARIES, we don't scan parts of stack */
/* segments that appear to be out of bounds. Thus we actually */
/* do both, which seems to yield the best results. */
# define USE_PROC_FOR_LIBRARIES
#endif
* TODO
# if defined(GC_LINUX_THREADS) && defined(REDIRECT_MALLOC) \
&& !defined(INCLUDE_LINUX_THREAD_DESCR)
/* Will not work, since libc and the dynamic loader use thread */
/* locals, sometimes as the only reference. */
# define INCLUDE_LINUX_THREAD_DESCR
# endif
* TODO
# if defined(UNIX_LIKE) && defined(THREADS) && !defined(NO_CANCEL_SAFE) \
&& !defined(PLATFORM_ANDROID)
/* Make the code cancellation-safe. This basically means that we */
/* ensure that cancellation requests are ignored while we are in */
/* the collector. This applies only to Posix deferred cancellation;*/
/* we don't handle Posix asynchronous cancellation. */
/* Note that this only works if pthread_setcancelstate is */
/* async-signal-safe, at least in the absence of asynchronous */
/* cancellation. This appears to be true for the glibc version, */
/* though it is not documented. Without that assumption, there */
/* seems to be no way to safely wait in a signal handler, which */
/* we need to do for thread suspension. */
/* Also note that little other code appears to be cancellation-safe.*/
/* Hence it may make sense to turn this off for performance. */
# define CANCEL_SAFE
# endif
* `CAN_SAVE_CALL_ARGS` vs. -fomit-frame-pointer now being on by
default for Linux x86 IIRC? (Which is an [[!taglink
open_issue_gcc]] for not including us.)
* TODO
# if defined(REDIRECT_MALLOC) && defined(THREADS) && !defined(LINUX)
# error "REDIRECT_MALLOC with THREADS works at most on Linux."
# endif
*HURD* has:
* `#define STACK_GROWS_DOWN`
* `#define HEURISTIC2`
Defined instead of `STACKBOTTOM` to have the value probed.
Linux also has this:
#if defined(LINUX_STACKBOTTOM) && defined(NO_PROC_STAT) \
&& !defined(USE_LIBC_PRIVATES)
/* This combination will fail, since we have no way to get */
/* the stack base. Use HEURISTIC2 instead. */
# undef LINUX_STACKBOTTOM
# define HEURISTIC2
/* This may still fail on some architectures like IA64. */
/* We tried ... */
#endif
Being on [[glibc]], we could perhaps do similar as `USE_LIBC_PRIVATES`
instead of `HEURISTIC2`. Pro: avoid `SIGSEGV` (and general fragility)
during probing at startup (if I'm understanding this correctly). Con:
rely on glibc internals. Or we instead add support to parse
[[`/proc/`|hurd/translator/procfs]] (can even use the same as Linux?),
or use some other interface. [[!tag open_issue_glibc]]
* `#define SIG_SUSPEND SIGUSR1`, `#define SIG_THR_RESTART SIGUSR2`
* We don't `#define MPROTECT_VDB` (WIP comment); but Linux neither.
* Where does our `GETPAGESIZE` come from? Should we `#include
<unistd.h>` like it is done for *LINUX*?
* `include/gc_pthread_redirects.h`
* TODO
Cancellation stuff is Linux-only. In other places, too.
* `mach_dep.c`
* `#define NO_GETCONTEXT`
[[!taglink open_issue_glibc]], but this is not a real problem here,
because we can use the following GCC internal function without much
overhead:
* `GC_with_callee_saves_pushed`
The `HAVE_BUILTIN_UNWIND_INIT` case is ours.
* `os_dep.c`
* `read`
Sure that it doesn't internally (in [[glibc]]) use `malloc`. Probably
only / mostly (?) a problem for `--enable-redirect-malloc`
configurations? Linux with threads uses `readv`.
* TODO.
* `dyn_load.c`
For `DYNAMIC_LOADING`. TODO.
* `pthread_support.c`, `pthread_stop_world.c`
TODO.
* TODO.
Other files also contain *LINUX* and other conditionals.
* `libatomic_ops/`
* `configure.ac`
Nothing.
* `Makefile`, `src/Makefile`, `src/atomic_ops/Makefile`,
`src/atomic_ops/sysdeps/Makefile`, `doc/Makefile`, `tests/Makefile`
Nothing.
* `src/atomic_ops/sysdeps/gcc/x86.h`
Nothing.
# Testsuite
There are different configurations possible, but in general, the testsuite
restults of GNU/Linux and GNU/Hurd look very similar.
It has last been run and compared on 2010-11-10, based on CVS HEAD sources from
2010-11-04, converted to [[Git, correspondingly
9abb37b2e581b415bb1f482085891a289c2c0be1|source_repositories/boehm_gc]].
## `--enable-cplusplus --enable-gc-debug`
* GNU/Hurd is missing *Call chain at allocation: [...] output*.
`os_dep.c`:`GC_print_callers`
# TODO
* Port stuff to [[/GCC]] / [[test it there|gcc/testsuite]].
* What are other applications to test Boehm GC? Also especially in
combination with [[/libpthread]] and dynamic loading of shared libraries?
* <http://www.hpl.hp.com/personal/Hans_Boehm/gc/#users>
|
