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[glibc.git] / nptl / sysdeps / pthread / createthread.c
blob66fafe805051740a7a95fc0cfb9da678102be20f
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.
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.
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.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18 02111-1307 USA. */
20 #include <sched.h>
21 #include <setjmp.h>
22 #include <signal.h>
23 #include <stdlib.h>
24 #include <atomic.h>
25 #include <ldsodefs.h>
26 #include <tls.h>
28 #include "kernel-features.h"
31 #define CLONE_SIGNAL (CLONE_SIGHAND | CLONE_THREAD)
33 /* Unless otherwise specified, the thread "register" is going to be
34 initialized with a pointer to the TCB. */
35 #ifndef TLS_VALUE
36 # define TLS_VALUE pd
37 #endif
39 #ifndef ARCH_CLONE
40 # define ARCH_CLONE __clone
41 #endif
44 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
45 /* Pointer to the corresponding variable in libc. */
46 int *__libc_multiple_threads_ptr attribute_hidden;
47 #endif
50 static int
51 do_clone (struct pthread *pd, const struct pthread_attr *attr,
52 int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
53 int stopped)
55 #ifdef PREPARE_CREATE
56 PREPARE_CREATE;
57 #endif
59 if (__builtin_expect (stopped != 0, 0))
60 /* We make sure the thread does not run far by forcing it to get a
61 lock. We lock it here too so that the new thread cannot continue
62 until we tell it to. */
63 lll_lock (pd->lock, LLL_PRIVATE);
65 /* One more thread. We cannot have the thread do this itself, since it
66 might exist but not have been scheduled yet by the time we've returned
67 and need to check the value to behave correctly. We must do it before
68 creating the thread, in case it does get scheduled first and then
69 might mistakenly think it was the only thread. In the failure case,
70 we momentarily store a false value; this doesn't matter because there
71 is no kosher thing a signal handler interrupting us right here can do
72 that cares whether the thread count is correct. */
73 atomic_increment (&__nptl_nthreads);
75 if (ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
76 pd, &pd->tid, TLS_VALUE, &pd->tid) == -1)
78 atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second. */
80 /* Failed. If the thread is detached, remove the TCB here since
81 the caller cannot do this. The caller remembered the thread
82 as detached and cannot reverify that it is not since it must
83 not access the thread descriptor again. */
84 if (IS_DETACHED (pd))
85 __deallocate_stack (pd);
87 /* We have to translate error codes. */
88 return errno == ENOMEM ? EAGAIN : errno;
91 /* Now we have the possibility to set scheduling parameters etc. */
92 if (__builtin_expect (stopped != 0, 0))
94 INTERNAL_SYSCALL_DECL (err);
95 int res = 0;
97 /* Set the affinity mask if necessary. */
98 if (attr->cpuset != NULL)
100 res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
101 attr->cpusetsize, attr->cpuset);
103 if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
105 /* The operation failed. We have to kill the thread. First
106 send it the cancellation signal. */
107 INTERNAL_SYSCALL_DECL (err2);
108 err_out:
109 #if __ASSUME_TGKILL
110 (void) INTERNAL_SYSCALL (tgkill, err2, 3,
111 THREAD_GETMEM (THREAD_SELF, pid),
112 pd->tid, SIGCANCEL);
113 #else
114 (void) INTERNAL_SYSCALL (tkill, err2, 2, pd->tid, SIGCANCEL);
115 #endif
117 return (INTERNAL_SYSCALL_ERROR_P (res, err)
118 ? INTERNAL_SYSCALL_ERRNO (res, err)
119 : 0);
123 /* Set the scheduling parameters. */
124 if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
126 res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
127 pd->schedpolicy, &pd->schedparam);
129 if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
130 goto err_out;
134 /* We now have for sure more than one thread. The main thread might
135 not yet have the flag set. No need to set the global variable
136 again if this is what we use. */
137 THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
139 return 0;
143 static int
144 create_thread (struct pthread *pd, const struct pthread_attr *attr,
145 STACK_VARIABLES_PARMS)
147 #ifdef TLS_TCB_AT_TP
148 assert (pd->header.tcb != NULL);
149 #endif
151 /* We rely heavily on various flags the CLONE function understands:
153 CLONE_VM, CLONE_FS, CLONE_FILES
154 These flags select semantics with shared address space and
155 file descriptors according to what POSIX requires.
157 CLONE_SIGNAL
158 This flag selects the POSIX signal semantics.
160 CLONE_SETTLS
161 The sixth parameter to CLONE determines the TLS area for the
162 new thread.
164 CLONE_PARENT_SETTID
165 The kernels writes the thread ID of the newly created thread
166 into the location pointed to by the fifth parameters to CLONE.
168 Note that it would be semantically equivalent to use
169 CLONE_CHILD_SETTID but it is be more expensive in the kernel.
171 CLONE_CHILD_CLEARTID
172 The kernels clears the thread ID of a thread that has called
173 sys_exit() in the location pointed to by the seventh parameter
174 to CLONE.
176 CLONE_DETACHED
177 No signal is generated if the thread exists and it is
178 automatically reaped.
180 The termination signal is chosen to be zero which means no signal
181 is sent. */
182 int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
183 | CLONE_SETTLS | CLONE_PARENT_SETTID
184 | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
185 #if __ASSUME_NO_CLONE_DETACHED == 0
186 | CLONE_DETACHED
187 #endif
188 | 0);
190 if (__builtin_expect (THREAD_GETMEM (THREAD_SELF, report_events), 0))
192 /* The parent thread is supposed to report events. Check whether
193 the TD_CREATE event is needed, too. */
194 const int _idx = __td_eventword (TD_CREATE);
195 const uint32_t _mask = __td_eventmask (TD_CREATE);
197 if ((_mask & (__nptl_threads_events.event_bits[_idx]
198 | pd->eventbuf.eventmask.event_bits[_idx])) != 0)
200 /* We always must have the thread start stopped. */
201 pd->stopped_start = true;
203 /* Create the thread. We always create the thread stopped
204 so that it does not get far before we tell the debugger. */
205 int res = do_clone (pd, attr, clone_flags, start_thread,
206 STACK_VARIABLES_ARGS, 1);
207 if (res == 0)
209 /* Now fill in the information about the new thread in
210 the newly created thread's data structure. We cannot let
211 the new thread do this since we don't know whether it was
212 already scheduled when we send the event. */
213 pd->eventbuf.eventnum = TD_CREATE;
214 pd->eventbuf.eventdata = pd;
216 /* Enqueue the descriptor. */
218 pd->nextevent = __nptl_last_event;
219 while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
220 pd, pd->nextevent)
221 != 0);
223 /* Now call the function which signals the event. */
224 __nptl_create_event ();
226 /* And finally restart the new thread. */
227 lll_unlock (pd->lock, LLL_PRIVATE);
230 return res;
234 #ifdef NEED_DL_SYSINFO
235 assert (THREAD_SELF_SYSINFO == THREAD_SYSINFO (pd));
236 #endif
238 /* Determine whether the newly created threads has to be started
239 stopped since we have to set the scheduling parameters or set the
240 affinity. */
241 bool stopped = false;
242 if (attr != NULL && (attr->cpuset != NULL
243 || (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
244 stopped = true;
245 pd->stopped_start = stopped;
246 pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
248 /* Actually create the thread. */
249 int res = do_clone (pd, attr, clone_flags, start_thread,
250 STACK_VARIABLES_ARGS, stopped);
252 if (res == 0 && stopped)
253 /* And finally restart the new thread. */
254 lll_unlock (pd->lock, LLL_PRIVATE);
256 return res;