1 /* Copyright (C) 2002-2007, 2008 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19 #include <sched.h>
20 #include <setjmp.h>
21 #include <signal.h>
22 #include <stdlib.h>
23 #include <atomic.h>
24 #include <ldsodefs.h>
25 #include <tls.h>
26
27 #include <bits/kernel-features.h>
28
29
30 #define CLONE_SIGNAL (CLONE_SIGHAND | CLONE_THREAD)
31
32 /* Unless otherwise specified, the thread "register" is going to be
33 initialized with a pointer to the TCB. */
34 #ifndef TLS_VALUE
35 # define TLS_VALUE pd
36 #endif
37
38 #ifndef ARCH_CLONE
39 # define ARCH_CLONE __clone
40 #endif
41
42
43 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
44 /* Pointer to the corresponding variable in libc. */
45 int *__libc_multiple_threads_ptr attribute_hidden;
46 #endif
47
48
49 static int
do_clone(struct pthread * pd,const struct pthread_attr * attr,int clone_flags,int (* fct)(void *),STACK_VARIABLES_PARMS,int stopped)50 do_clone (struct pthread *pd, const struct pthread_attr *attr,
51 int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
52 int stopped)
53 {
54 #ifdef PREPARE_CREATE
55 PREPARE_CREATE;
56 #endif
57
58 if (__builtin_expect (stopped != 0, 0))
59 /* We make sure the thread does not run far by forcing it to get a
60 lock. We lock it here too so that the new thread cannot continue
61 until we tell it to. */
62 lll_lock (pd->lock, LLL_PRIVATE);
63
64 /* One more thread. We cannot have the thread do this itself, since it
65 might exist but not have been scheduled yet by the time we've returned
66 and need to check the value to behave correctly. We must do it before
67 creating the thread, in case it does get scheduled first and then
68 might mistakenly think it was the only thread. In the failure case,
69 we momentarily store a false value; this doesn't matter because there
70 is no kosher thing a signal handler interrupting us right here can do
71 that cares whether the thread count is correct. */
72 atomic_increment (&__nptl_nthreads);
73
74 if (ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
75 pd, &pd->tid, TLS_VALUE, &pd->tid) == -1)
76 {
77 atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second. */
78
79 /* Failed. If the thread is detached, remove the TCB here since
80 the caller cannot do this. The caller remembered the thread
81 as detached and cannot reverify that it is not since it must
82 not access the thread descriptor again. */
83 if (IS_DETACHED (pd))
84 __deallocate_stack (pd);
85
86 /* We have to translate error codes. */
87 return errno == ENOMEM ? EAGAIN : errno;
88 }
89
90 /* Now we have the possibility to set scheduling parameters etc. */
91 if (__builtin_expect (stopped != 0, 0))
92 {
93 INTERNAL_SYSCALL_DECL (err);
94 int res = 0;
95
96 /* Set the affinity mask if necessary. */
97 if (attr->cpuset != NULL)
98 {
99 res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
100 attr->cpusetsize, attr->cpuset);
101
102 if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
103 {
104 /* The operation failed. We have to kill the thread. First
105 send it the cancellation signal. */
106 INTERNAL_SYSCALL_DECL (err2);
107 err_out:
108 #if defined (__ASSUME_TGKILL) && __ASSUME_TGKILL
109 (void) INTERNAL_SYSCALL (tgkill, err2, 3,
110 THREAD_GETMEM (THREAD_SELF, pid),
111 pd->tid, SIGCANCEL);
112 #else
113 (void) INTERNAL_SYSCALL (tkill, err2, 2, pd->tid, SIGCANCEL);
114 #endif
115
116 return (INTERNAL_SYSCALL_ERROR_P (res, err)
117 ? INTERNAL_SYSCALL_ERRNO (res, err)
118 : 0);
119 }
120 }
121
122 /* Set the scheduling parameters. */
123 if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
124 {
125 res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
126 pd->schedpolicy, &pd->schedparam);
127
128 if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
129 goto err_out;
130 }
131 }
132
133 /* We now have for sure more than one thread. The main thread might
134 not yet have the flag set. No need to set the global variable
135 again if this is what we use. */
136 THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
137
138 return 0;
139 }
140
141
142 static int
create_thread(struct pthread * pd,const struct pthread_attr * attr,STACK_VARIABLES_PARMS)143 create_thread (struct pthread *pd, const struct pthread_attr *attr,
144 STACK_VARIABLES_PARMS)
145 {
146 #ifdef TLS_TCB_AT_TP
147 assert (pd->header.tcb != NULL);
148 #endif
149
150 /* We rely heavily on various flags the CLONE function understands:
151
152 CLONE_VM, CLONE_FS, CLONE_FILES
153 These flags select semantics with shared address space and
154 file descriptors according to what POSIX requires.
155
156 CLONE_SIGNAL
157 This flag selects the POSIX signal semantics.
158
159 CLONE_SETTLS
160 The sixth parameter to CLONE determines the TLS area for the
161 new thread.
162
163 CLONE_PARENT_SETTID
164 The kernels writes the thread ID of the newly created thread
165 into the location pointed to by the fifth parameters to CLONE.
166
167 Note that it would be semantically equivalent to use
168 CLONE_CHILD_SETTID but it is be more expensive in the kernel.
169
170 CLONE_CHILD_CLEARTID
171 The kernels clears the thread ID of a thread that has called
172 sys_exit() in the location pointed to by the seventh parameter
173 to CLONE.
174
175 CLONE_DETACHED
176 No signal is generated if the thread exists and it is
177 automatically reaped.
178
179 The termination signal is chosen to be zero which means no signal
180 is sent. */
181 int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
182 | CLONE_SETTLS | CLONE_PARENT_SETTID
183 | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
184 #if __ASSUME_NO_CLONE_DETACHED == 0
185 | CLONE_DETACHED
186 #endif
187 | 0);
188
189 if (__builtin_expect (THREAD_GETMEM (THREAD_SELF, report_events), 0))
190 {
191 /* The parent thread is supposed to report events. Check whether
192 the TD_CREATE event is needed, too. */
193 const int _idx = __td_eventword (TD_CREATE);
194 const uint32_t _mask = __td_eventmask (TD_CREATE);
195
196 if ((_mask & (__nptl_threads_events.event_bits[_idx]
197 | pd->eventbuf.eventmask.event_bits[_idx])) != 0)
198 {
199 /* We always must have the thread start stopped. */
200 pd->stopped_start = true;
201
202 /* Create the thread. We always create the thread stopped
203 so that it does not get far before we tell the debugger. */
204 int res = do_clone (pd, attr, clone_flags, start_thread,
205 STACK_VARIABLES_ARGS, 1);
206 if (res == 0)
207 {
208 /* Now fill in the information about the new thread in
209 the newly created thread's data structure. We cannot let
210 the new thread do this since we don't know whether it was
211 already scheduled when we send the event. */
212 pd->eventbuf.eventnum = TD_CREATE;
213 pd->eventbuf.eventdata = pd;
214
215 /* Enqueue the descriptor. */
216 do
217 pd->nextevent = __nptl_last_event;
218 while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
219 pd, pd->nextevent)
220 != 0);
221
222 /* Now call the function which signals the event. */
223 __nptl_create_event ();
224
225 /* And finally restart the new thread. */
226 lll_unlock (pd->lock, LLL_PRIVATE);
227 }
228
229 return res;
230 }
231 }
232
233 #ifdef NEED_DL_SYSINFO
234 assert (THREAD_SELF_SYSINFO == THREAD_SYSINFO (pd));
235 #endif
236
237 /* Determine whether the newly created threads has to be started
238 stopped since we have to set the scheduling parameters or set the
239 affinity. */
240 bool stopped = false;
241 if (attr != NULL && (attr->cpuset != NULL
242 || (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
243 stopped = true;
244 pd->stopped_start = stopped;
245 pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
246
247 /* Actually create the thread. */
248 int res = do_clone (pd, attr, clone_flags, start_thread,
249 STACK_VARIABLES_ARGS, stopped);
250
251 if (res == 0 && stopped)
252 /* And finally restart the new thread. */
253 lll_unlock (pd->lock, LLL_PRIVATE);
254
255 return res;
256 }
257