1/* Copyright (C) 2002-2019 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 <ctype.h>
20#include <errno.h>
21#include <stdbool.h>
22#include <stdlib.h>
23#include <string.h>
24#include <stdint.h>
25#include "pthreadP.h"
26#include <hp-timing.h>
27#include <ldsodefs.h>
28#include <atomic.h>
29#include <libc-internal.h>
30#include <resolv.h>
31#include <kernel-features.h>
32#include <exit-thread.h>
33#include <default-sched.h>
34#include <futex-internal.h>
35#include <tls-setup.h>
36#include "libioP.h"
37
38#include <shlib-compat.h>
39
40#include <stap-probe.h>
41
42
43/* Nozero if debugging mode is enabled. */
44int __pthread_debug;
45
46/* Globally enabled events. */
47static td_thr_events_t __nptl_threads_events __attribute_used__;
48
49/* Pointer to descriptor with the last event. */
50static struct pthread *__nptl_last_event __attribute_used__;
51
52/* Number of threads running. */
53unsigned int __nptl_nthreads = 1;
54
55
56/* Code to allocate and deallocate a stack. */
57#include "allocatestack.c"
58
59/* CONCURRENCY NOTES:
60
61 Understanding who is the owner of the 'struct pthread' or 'PD'
62 (refers to the value of the 'struct pthread *pd' function argument)
63 is critically important in determining exactly which operations are
64 allowed and which are not and when, particularly when it comes to the
65 implementation of pthread_create, pthread_join, pthread_detach, and
66 other functions which all operate on PD.
67
68 The owner of PD is responsible for freeing the final resources
69 associated with PD, and may examine the memory underlying PD at any
70 point in time until it frees it back to the OS or to reuse by the
71 runtime.
72
73 The thread which calls pthread_create is called the creating thread.
74 The creating thread begins as the owner of PD.
75
76 During startup the new thread may examine PD in coordination with the
77 owner thread (which may be itself).
78
79 The four cases of ownership transfer are:
80
81 (1) Ownership of PD is released to the process (all threads may use it)
82 after the new thread starts in a joinable state
83 i.e. pthread_create returns a usable pthread_t.
84
85 (2) Ownership of PD is released to the new thread starting in a detached
86 state.
87
88 (3) Ownership of PD is dynamically released to a running thread via
89 pthread_detach.
90
91 (4) Ownership of PD is acquired by the thread which calls pthread_join.
92
93 Implementation notes:
94
95 The PD->stopped_start and thread_ran variables are used to determine
96 exactly which of the four ownership states we are in and therefore
97 what actions can be taken. For example after (2) we cannot read or
98 write from PD anymore since the thread may no longer exist and the
99 memory may be unmapped.
100
101 It is important to point out that PD->lock is being used both
102 similar to a one-shot semaphore and subsequently as a mutex. The
103 lock is taken in the parent to force the child to wait, and then the
104 child releases the lock. However, this semaphore-like effect is used
105 only for synchronizing the parent and child. After startup the lock
106 is used like a mutex to create a critical section during which a
107 single owner modifies the thread parameters.
108
109 The most complicated cases happen during thread startup:
110
111 (a) If the created thread is in a detached (PTHREAD_CREATE_DETACHED),
112 or joinable (default PTHREAD_CREATE_JOINABLE) state and
113 STOPPED_START is true, then the creating thread has ownership of
114 PD until the PD->lock is released by pthread_create. If any
115 errors occur we are in states (c), (d), or (e) below.
116
117 (b) If the created thread is in a detached state
118 (PTHREAD_CREATED_DETACHED), and STOPPED_START is false, then the
119 creating thread has ownership of PD until it invokes the OS
120 kernel's thread creation routine. If this routine returns
121 without error, then the created thread owns PD; otherwise, see
122 (c) and (e) below.
123
124 (c) If the detached thread setup failed and THREAD_RAN is true, then
125 the creating thread releases ownership to the new thread by
126 sending a cancellation signal. All threads set THREAD_RAN to
127 true as quickly as possible after returning from the OS kernel's
128 thread creation routine.
129
130 (d) If the joinable thread setup failed and THREAD_RAN is true, then
131 then the creating thread retains ownership of PD and must cleanup
132 state. Ownership cannot be released to the process via the
133 return of pthread_create since a non-zero result entails PD is
134 undefined and therefore cannot be joined to free the resources.
135 We privately call pthread_join on the thread to finish handling
136 the resource shutdown (Or at least we should, see bug 19511).
137
138 (e) If the thread creation failed and THREAD_RAN is false, then the
139 creating thread retains ownership of PD and must cleanup state.
140 No waiting for the new thread is required because it never
141 started.
142
143 The nptl_db interface:
144
145 The interface with nptl_db requires that we enqueue PD into a linked
146 list and then call a function which the debugger will trap. The PD
147 will then be dequeued and control returned to the thread. The caller
148 at the time must have ownership of PD and such ownership remains
149 after control returns to thread. The enqueued PD is removed from the
150 linked list by the nptl_db callback td_thr_event_getmsg. The debugger
151 must ensure that the thread does not resume execution, otherwise
152 ownership of PD may be lost and examining PD will not be possible.
153
154 Note that the GNU Debugger as of (December 10th 2015) commit
155 c2c2a31fdb228d41ce3db62b268efea04bd39c18 no longer uses
156 td_thr_event_getmsg and several other related nptl_db interfaces. The
157 principal reason for this is that nptl_db does not support non-stop
158 mode where other threads can run concurrently and modify runtime
159 structures currently in use by the debugger and the nptl_db
160 interface.
161
162 Axioms:
163
164 * The create_thread function can never set stopped_start to false.
165 * The created thread can read stopped_start but never write to it.
166 * The variable thread_ran is set some time after the OS thread
167 creation routine returns, how much time after the thread is created
168 is unspecified, but it should be as quickly as possible.
169
170*/
171
172/* CREATE THREAD NOTES:
173
174 createthread.c defines the create_thread function, and two macros:
175 START_THREAD_DEFN and START_THREAD_SELF (see below).
176
177 create_thread must initialize PD->stopped_start. It should be true
178 if the STOPPED_START parameter is true, or if create_thread needs the
179 new thread to synchronize at startup for some other implementation
180 reason. If STOPPED_START will be true, then create_thread is obliged
181 to lock PD->lock before starting the thread. Then pthread_create
182 unlocks PD->lock which synchronizes-with START_THREAD_DEFN in the
183 child thread which does an acquire/release of PD->lock as the last
184 action before calling the user entry point. The goal of all of this
185 is to ensure that the required initial thread attributes are applied
186 (by the creating thread) before the new thread runs user code. Note
187 that the the functions pthread_getschedparam, pthread_setschedparam,
188 pthread_setschedprio, __pthread_tpp_change_priority, and
189 __pthread_current_priority reuse the same lock, PD->lock, for a
190 similar purpose e.g. synchronizing the setting of similar thread
191 attributes. These functions are never called before the thread is
192 created, so don't participate in startup syncronization, but given
193 that the lock is present already and in the unlocked state, reusing
194 it saves space.
195
196 The return value is zero for success or an errno code for failure.
197 If the return value is ENOMEM, that will be translated to EAGAIN,
198 so create_thread need not do that. On failure, *THREAD_RAN should
199 be set to true iff the thread actually started up and then got
200 canceled before calling user code (*PD->start_routine). */
201static int create_thread (struct pthread *pd, const struct pthread_attr *attr,
202 bool *stopped_start, STACK_VARIABLES_PARMS,
203 bool *thread_ran);
204
205#include <createthread.c>
206
207
208struct pthread *
209__find_in_stack_list (struct pthread *pd)
210{
211 list_t *entry;
212 struct pthread *result = NULL;
213
214 lll_lock (stack_cache_lock, LLL_PRIVATE);
215
216 list_for_each (entry, &stack_used)
217 {
218 struct pthread *curp;
219
220 curp = list_entry (entry, struct pthread, list);
221 if (curp == pd)
222 {
223 result = curp;
224 break;
225 }
226 }
227
228 if (result == NULL)
229 list_for_each (entry, &__stack_user)
230 {
231 struct pthread *curp;
232
233 curp = list_entry (entry, struct pthread, list);
234 if (curp == pd)
235 {
236 result = curp;
237 break;
238 }
239 }
240
241 lll_unlock (stack_cache_lock, LLL_PRIVATE);
242
243 return result;
244}
245
246
247/* Deallocate POSIX thread-local-storage. */
248void
249attribute_hidden
250__nptl_deallocate_tsd (void)
251{
252 struct pthread *self = THREAD_SELF;
253
254 /* Maybe no data was ever allocated. This happens often so we have
255 a flag for this. */
256 if (THREAD_GETMEM (self, specific_used))
257 {
258 size_t round;
259 size_t cnt;
260
261 round = 0;
262 do
263 {
264 size_t idx;
265
266 /* So far no new nonzero data entry. */
267 THREAD_SETMEM (self, specific_used, false);
268
269 for (cnt = idx = 0; cnt < PTHREAD_KEY_1STLEVEL_SIZE; ++cnt)
270 {
271 struct pthread_key_data *level2;
272
273 level2 = THREAD_GETMEM_NC (self, specific, cnt);
274
275 if (level2 != NULL)
276 {
277 size_t inner;
278
279 for (inner = 0; inner < PTHREAD_KEY_2NDLEVEL_SIZE;
280 ++inner, ++idx)
281 {
282 void *data = level2[inner].data;
283
284 if (data != NULL)
285 {
286 /* Always clear the data. */
287 level2[inner].data = NULL;
288
289 /* Make sure the data corresponds to a valid
290 key. This test fails if the key was
291 deallocated and also if it was
292 re-allocated. It is the user's
293 responsibility to free the memory in this
294 case. */
295 if (level2[inner].seq
296 == __pthread_keys[idx].seq
297 /* It is not necessary to register a destructor
298 function. */
299 && __pthread_keys[idx].destr != NULL)
300 /* Call the user-provided destructor. */
301 __pthread_keys[idx].destr (data);
302 }
303 }
304 }
305 else
306 idx += PTHREAD_KEY_1STLEVEL_SIZE;
307 }
308
309 if (THREAD_GETMEM (self, specific_used) == 0)
310 /* No data has been modified. */
311 goto just_free;
312 }
313 /* We only repeat the process a fixed number of times. */
314 while (__builtin_expect (++round < PTHREAD_DESTRUCTOR_ITERATIONS, 0));
315
316 /* Just clear the memory of the first block for reuse. */
317 memset (&THREAD_SELF->specific_1stblock, '\0',
318 sizeof (self->specific_1stblock));
319
320 just_free:
321 /* Free the memory for the other blocks. */
322 for (cnt = 1; cnt < PTHREAD_KEY_1STLEVEL_SIZE; ++cnt)
323 {
324 struct pthread_key_data *level2;
325
326 level2 = THREAD_GETMEM_NC (self, specific, cnt);
327 if (level2 != NULL)
328 {
329 /* The first block is allocated as part of the thread
330 descriptor. */
331 free (level2);
332 THREAD_SETMEM_NC (self, specific, cnt, NULL);
333 }
334 }
335
336 THREAD_SETMEM (self, specific_used, false);
337 }
338}
339
340
341/* Deallocate a thread's stack after optionally making sure the thread
342 descriptor is still valid. */
343void
344__free_tcb (struct pthread *pd)
345{
346 /* The thread is exiting now. */
347 if (__builtin_expect (atomic_bit_test_set (&pd->cancelhandling,
348 TERMINATED_BIT) == 0, 1))
349 {
350 /* Remove the descriptor from the list. */
351 if (DEBUGGING_P && __find_in_stack_list (pd) == NULL)
352 /* Something is really wrong. The descriptor for a still
353 running thread is gone. */
354 abort ();
355
356 /* Free TPP data. */
357 if (__glibc_unlikely (pd->tpp != NULL))
358 {
359 struct priority_protection_data *tpp = pd->tpp;
360
361 pd->tpp = NULL;
362 free (tpp);
363 }
364
365 /* Queue the stack memory block for reuse and exit the process. The
366 kernel will signal via writing to the address returned by
367 QUEUE-STACK when the stack is available. */
368 __deallocate_stack (pd);
369 }
370}
371
372
373/* Local function to start thread and handle cleanup.
374 createthread.c defines the macro START_THREAD_DEFN to the
375 declaration that its create_thread function will refer to, and
376 START_THREAD_SELF to the expression to optimally deliver the new
377 thread's THREAD_SELF value. */
378START_THREAD_DEFN
379{
380 struct pthread *pd = START_THREAD_SELF;
381
382 /* Initialize resolver state pointer. */
383 __resp = &pd->res;
384
385 /* Initialize pointers to locale data. */
386 __ctype_init ();
387
388 /* Allow setxid from now onwards. */
389 if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0) == -2))
390 futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
391
392#ifdef __NR_set_robust_list
393# ifndef __ASSUME_SET_ROBUST_LIST
394 if (__set_robust_list_avail >= 0)
395# endif
396 {
397 INTERNAL_SYSCALL_DECL (err);
398 /* This call should never fail because the initial call in init.c
399 succeeded. */
400 INTERNAL_SYSCALL (set_robust_list, err, 2, &pd->robust_head,
401 sizeof (struct robust_list_head));
402 }
403#endif
404
405#ifdef SIGCANCEL
406 /* If the parent was running cancellation handlers while creating
407 the thread the new thread inherited the signal mask. Reset the
408 cancellation signal mask. */
409 if (__glibc_unlikely (pd->parent_cancelhandling & CANCELING_BITMASK))
410 {
411 INTERNAL_SYSCALL_DECL (err);
412 sigset_t mask;
413 __sigemptyset (&mask);
414 __sigaddset (&mask, SIGCANCEL);
415 (void) INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_UNBLOCK, &mask,
416 NULL, _NSIG / 8);
417 }
418#endif
419
420 /* This is where the try/finally block should be created. For
421 compilers without that support we do use setjmp. */
422 struct pthread_unwind_buf unwind_buf;
423
424 int not_first_call;
425 not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
426
427 /* No previous handlers. NB: This must be done after setjmp since the
428 private space in the unwind jump buffer may overlap space used by
429 setjmp to store extra architecture-specific information which is
430 never used by the cancellation-specific __libc_unwind_longjmp.
431
432 The private space is allowed to overlap because the unwinder never
433 has to return through any of the jumped-to call frames, and thus
434 only a minimum amount of saved data need be stored, and for example,
435 need not include the process signal mask information. This is all
436 an optimization to reduce stack usage when pushing cancellation
437 handlers. */
438 unwind_buf.priv.data.prev = NULL;
439 unwind_buf.priv.data.cleanup = NULL;
440
441 if (__glibc_likely (! not_first_call))
442 {
443 /* Store the new cleanup handler info. */
444 THREAD_SETMEM (pd, cleanup_jmp_buf, &unwind_buf);
445
446 /* We are either in (a) or (b), and in either case we either own
447 PD already (2) or are about to own PD (1), and so our only
448 restriction would be that we can't free PD until we know we
449 have ownership (see CONCURRENCY NOTES above). */
450 if (__glibc_unlikely (pd->stopped_start))
451 {
452 int oldtype = CANCEL_ASYNC ();
453
454 /* Get the lock the parent locked to force synchronization. */
455 lll_lock (pd->lock, LLL_PRIVATE);
456
457 /* We have ownership of PD now. */
458
459 /* And give it up right away. */
460 lll_unlock (pd->lock, LLL_PRIVATE);
461
462 CANCEL_RESET (oldtype);
463 }
464
465 LIBC_PROBE (pthread_start, 3, (pthread_t) pd, pd->start_routine, pd->arg);
466
467 /* Run the code the user provided. */
468 void *ret;
469 if (pd->c11)
470 {
471 /* The function pointer of the c11 thread start is cast to an incorrect
472 type on __pthread_create_2_1 call, however it is casted back to correct
473 one so the call behavior is well-defined (it is assumed that pointers
474 to void are able to represent all values of int. */
475 int (*start)(void*) = (int (*) (void*)) pd->start_routine;
476 ret = (void*) (uintptr_t) start (pd->arg);
477 }
478 else
479 ret = pd->start_routine (pd->arg);
480 THREAD_SETMEM (pd, result, ret);
481 }
482
483 /* Call destructors for the thread_local TLS variables. */
484#ifndef SHARED
485 if (&__call_tls_dtors != NULL)
486#endif
487 __call_tls_dtors ();
488
489 /* Run the destructor for the thread-local data. */
490 __nptl_deallocate_tsd ();
491
492 /* Clean up any state libc stored in thread-local variables. */
493 __libc_thread_freeres ();
494
495 /* If this is the last thread we terminate the process now. We
496 do not notify the debugger, it might just irritate it if there
497 is no thread left. */
498 if (__glibc_unlikely (atomic_decrement_and_test (&__nptl_nthreads)))
499 /* This was the last thread. */
500 exit (0);
501
502 /* Report the death of the thread if this is wanted. */
503 if (__glibc_unlikely (pd->report_events))
504 {
505 /* See whether TD_DEATH is in any of the mask. */
506 const int idx = __td_eventword (TD_DEATH);
507 const uint32_t mask = __td_eventmask (TD_DEATH);
508
509 if ((mask & (__nptl_threads_events.event_bits[idx]
510 | pd->eventbuf.eventmask.event_bits[idx])) != 0)
511 {
512 /* Yep, we have to signal the death. Add the descriptor to
513 the list but only if it is not already on it. */
514 if (pd->nextevent == NULL)
515 {
516 pd->eventbuf.eventnum = TD_DEATH;
517 pd->eventbuf.eventdata = pd;
518
519 do
520 pd->nextevent = __nptl_last_event;
521 while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
522 pd, pd->nextevent));
523 }
524
525 /* Now call the function which signals the event. See
526 CONCURRENCY NOTES for the nptl_db interface comments. */
527 __nptl_death_event ();
528 }
529 }
530
531 /* The thread is exiting now. Don't set this bit until after we've hit
532 the event-reporting breakpoint, so that td_thr_get_info on us while at
533 the breakpoint reports TD_THR_RUN state rather than TD_THR_ZOMBIE. */
534 atomic_bit_set (&pd->cancelhandling, EXITING_BIT);
535
536#ifndef __ASSUME_SET_ROBUST_LIST
537 /* If this thread has any robust mutexes locked, handle them now. */
538# if __PTHREAD_MUTEX_HAVE_PREV
539 void *robust = pd->robust_head.list;
540# else
541 __pthread_slist_t *robust = pd->robust_list.__next;
542# endif
543 /* We let the kernel do the notification if it is able to do so.
544 If we have to do it here there for sure are no PI mutexes involved
545 since the kernel support for them is even more recent. */
546 if (__set_robust_list_avail < 0
547 && __builtin_expect (robust != (void *) &pd->robust_head, 0))
548 {
549 do
550 {
551 struct __pthread_mutex_s *this = (struct __pthread_mutex_s *)
552 ((char *) robust - offsetof (struct __pthread_mutex_s,
553 __list.__next));
554 robust = *((void **) robust);
555
556# if __PTHREAD_MUTEX_HAVE_PREV
557 this->__list.__prev = NULL;
558# endif
559 this->__list.__next = NULL;
560
561 atomic_or (&this->__lock, FUTEX_OWNER_DIED);
562 futex_wake ((unsigned int *) &this->__lock, 1,
563 /* XYZ */ FUTEX_SHARED);
564 }
565 while (robust != (void *) &pd->robust_head);
566 }
567#endif
568
569 advise_stack_range (pd->stackblock, pd->stackblock_size, (uintptr_t) pd,
570 pd->guardsize);
571
572 /* If the thread is detached free the TCB. */
573 if (IS_DETACHED (pd))
574 /* Free the TCB. */
575 __free_tcb (pd);
576 else if (__glibc_unlikely (pd->cancelhandling & SETXID_BITMASK))
577 {
578 /* Some other thread might call any of the setXid functions and expect
579 us to reply. In this case wait until we did that. */
580 do
581 /* XXX This differs from the typical futex_wait_simple pattern in that
582 the futex_wait condition (setxid_futex) is different from the
583 condition used in the surrounding loop (cancelhandling). We need
584 to check and document why this is correct. */
585 futex_wait_simple (&pd->setxid_futex, 0, FUTEX_PRIVATE);
586 while (pd->cancelhandling & SETXID_BITMASK);
587
588 /* Reset the value so that the stack can be reused. */
589 pd->setxid_futex = 0;
590 }
591
592 /* We cannot call '_exit' here. '_exit' will terminate the process.
593
594 The 'exit' implementation in the kernel will signal when the
595 process is really dead since 'clone' got passed the CLONE_CHILD_CLEARTID
596 flag. The 'tid' field in the TCB will be set to zero.
597
598 The exit code is zero since in case all threads exit by calling
599 'pthread_exit' the exit status must be 0 (zero). */
600 __exit_thread ();
601
602 /* NOTREACHED */
603}
604
605
606/* Return true iff obliged to report TD_CREATE events. */
607static bool
608report_thread_creation (struct pthread *pd)
609{
610 if (__glibc_unlikely (THREAD_GETMEM (THREAD_SELF, report_events)))
611 {
612 /* The parent thread is supposed to report events.
613 Check whether the TD_CREATE event is needed, too. */
614 const size_t idx = __td_eventword (TD_CREATE);
615 const uint32_t mask = __td_eventmask (TD_CREATE);
616
617 return ((mask & (__nptl_threads_events.event_bits[idx]
618 | pd->eventbuf.eventmask.event_bits[idx])) != 0);
619 }
620 return false;
621}
622
623
624int
625__pthread_create_2_1 (pthread_t *newthread, const pthread_attr_t *attr,
626 void *(*start_routine) (void *), void *arg)
627{
628 STACK_VARIABLES;
629
630 const struct pthread_attr *iattr = (struct pthread_attr *) attr;
631 struct pthread_attr default_attr;
632 bool free_cpuset = false;
633 bool c11 = (attr == ATTR_C11_THREAD);
634 if (iattr == NULL || c11)
635 {
636 lll_lock (__default_pthread_attr_lock, LLL_PRIVATE);
637 default_attr = __default_pthread_attr;
638 size_t cpusetsize = default_attr.cpusetsize;
639 if (cpusetsize > 0)
640 {
641 cpu_set_t *cpuset;
642 if (__glibc_likely (__libc_use_alloca (cpusetsize)))
643 cpuset = __alloca (cpusetsize);
644 else
645 {
646 cpuset = malloc (cpusetsize);
647 if (cpuset == NULL)
648 {
649 lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
650 return ENOMEM;
651 }
652 free_cpuset = true;
653 }
654 memcpy (cpuset, default_attr.cpuset, cpusetsize);
655 default_attr.cpuset = cpuset;
656 }
657 lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
658 iattr = &default_attr;
659 }
660
661 struct pthread *pd = NULL;
662 int err = ALLOCATE_STACK (iattr, &pd);
663 int retval = 0;
664
665 if (__glibc_unlikely (err != 0))
666 /* Something went wrong. Maybe a parameter of the attributes is
667 invalid or we could not allocate memory. Note we have to
668 translate error codes. */
669 {
670 retval = err == ENOMEM ? EAGAIN : err;
671 goto out;
672 }
673
674
675 /* Initialize the TCB. All initializations with zero should be
676 performed in 'get_cached_stack'. This way we avoid doing this if
677 the stack freshly allocated with 'mmap'. */
678
679#if TLS_TCB_AT_TP
680 /* Reference to the TCB itself. */
681 pd->header.self = pd;
682
683 /* Self-reference for TLS. */
684 pd->header.tcb = pd;
685#endif
686
687 /* Store the address of the start routine and the parameter. Since
688 we do not start the function directly the stillborn thread will
689 get the information from its thread descriptor. */
690 pd->start_routine = start_routine;
691 pd->arg = arg;
692 pd->c11 = c11;
693
694 /* Copy the thread attribute flags. */
695 struct pthread *self = THREAD_SELF;
696 pd->flags = ((iattr->flags & ~(ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET))
697 | (self->flags & (ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET)));
698
699 /* Initialize the field for the ID of the thread which is waiting
700 for us. This is a self-reference in case the thread is created
701 detached. */
702 pd->joinid = iattr->flags & ATTR_FLAG_DETACHSTATE ? pd : NULL;
703
704 /* The debug events are inherited from the parent. */
705 pd->eventbuf = self->eventbuf;
706
707
708 /* Copy the parent's scheduling parameters. The flags will say what
709 is valid and what is not. */
710 pd->schedpolicy = self->schedpolicy;
711 pd->schedparam = self->schedparam;
712
713 /* Copy the stack guard canary. */
714#ifdef THREAD_COPY_STACK_GUARD
715 THREAD_COPY_STACK_GUARD (pd);
716#endif
717
718 /* Copy the pointer guard value. */
719#ifdef THREAD_COPY_POINTER_GUARD
720 THREAD_COPY_POINTER_GUARD (pd);
721#endif
722
723 /* Setup tcbhead. */
724 tls_setup_tcbhead (pd);
725
726 /* Verify the sysinfo bits were copied in allocate_stack if needed. */
727#ifdef NEED_DL_SYSINFO
728 CHECK_THREAD_SYSINFO (pd);
729#endif
730
731 /* Inform start_thread (above) about cancellation state that might
732 translate into inherited signal state. */
733 pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
734
735 /* Determine scheduling parameters for the thread. */
736 if (__builtin_expect ((iattr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0, 0)
737 && (iattr->flags & (ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET)) != 0)
738 {
739 /* Use the scheduling parameters the user provided. */
740 if (iattr->flags & ATTR_FLAG_POLICY_SET)
741 {
742 pd->schedpolicy = iattr->schedpolicy;
743 pd->flags |= ATTR_FLAG_POLICY_SET;
744 }
745 if (iattr->flags & ATTR_FLAG_SCHED_SET)
746 {
747 /* The values were validated in pthread_attr_setschedparam. */
748 pd->schedparam = iattr->schedparam;
749 pd->flags |= ATTR_FLAG_SCHED_SET;
750 }
751
752 if ((pd->flags & (ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET))
753 != (ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET))
754 collect_default_sched (pd);
755 }
756
757 if (__glibc_unlikely (__nptl_nthreads == 1))
758 _IO_enable_locks ();
759
760 /* Pass the descriptor to the caller. */
761 *newthread = (pthread_t) pd;
762
763 LIBC_PROBE (pthread_create, 4, newthread, attr, start_routine, arg);
764
765 /* One more thread. We cannot have the thread do this itself, since it
766 might exist but not have been scheduled yet by the time we've returned
767 and need to check the value to behave correctly. We must do it before
768 creating the thread, in case it does get scheduled first and then
769 might mistakenly think it was the only thread. In the failure case,
770 we momentarily store a false value; this doesn't matter because there
771 is no kosher thing a signal handler interrupting us right here can do
772 that cares whether the thread count is correct. */
773 atomic_increment (&__nptl_nthreads);
774
775 /* Our local value of stopped_start and thread_ran can be accessed at
776 any time. The PD->stopped_start may only be accessed if we have
777 ownership of PD (see CONCURRENCY NOTES above). */
778 bool stopped_start = false; bool thread_ran = false;
779
780 /* Start the thread. */
781 if (__glibc_unlikely (report_thread_creation (pd)))
782 {
783 stopped_start = true;
784
785 /* We always create the thread stopped at startup so we can
786 notify the debugger. */
787 retval = create_thread (pd, iattr, &stopped_start,
788 STACK_VARIABLES_ARGS, &thread_ran);
789 if (retval == 0)
790 {
791 /* We retain ownership of PD until (a) (see CONCURRENCY NOTES
792 above). */
793
794 /* Assert stopped_start is true in both our local copy and the
795 PD copy. */
796 assert (stopped_start);
797 assert (pd->stopped_start);
798
799 /* Now fill in the information about the new thread in
800 the newly created thread's data structure. We cannot let
801 the new thread do this since we don't know whether it was
802 already scheduled when we send the event. */
803 pd->eventbuf.eventnum = TD_CREATE;
804 pd->eventbuf.eventdata = pd;
805
806 /* Enqueue the descriptor. */
807 do
808 pd->nextevent = __nptl_last_event;
809 while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
810 pd, pd->nextevent)
811 != 0);
812
813 /* Now call the function which signals the event. See
814 CONCURRENCY NOTES for the nptl_db interface comments. */
815 __nptl_create_event ();
816 }
817 }
818 else
819 retval = create_thread (pd, iattr, &stopped_start,
820 STACK_VARIABLES_ARGS, &thread_ran);
821
822 if (__glibc_unlikely (retval != 0))
823 {
824 if (thread_ran)
825 /* State (c) or (d) and we may not have PD ownership (see
826 CONCURRENCY NOTES above). We can assert that STOPPED_START
827 must have been true because thread creation didn't fail, but
828 thread attribute setting did. */
829 /* See bug 19511 which explains why doing nothing here is a
830 resource leak for a joinable thread. */
831 assert (stopped_start);
832 else
833 {
834 /* State (e) and we have ownership of PD (see CONCURRENCY
835 NOTES above). */
836
837 /* Oops, we lied for a second. */
838 atomic_decrement (&__nptl_nthreads);
839
840 /* Perhaps a thread wants to change the IDs and is waiting for this
841 stillborn thread. */
842 if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0)
843 == -2))
844 futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
845
846 /* Free the resources. */
847 __deallocate_stack (pd);
848 }
849
850 /* We have to translate error codes. */
851 if (retval == ENOMEM)
852 retval = EAGAIN;
853 }
854 else
855 {
856 /* We don't know if we have PD ownership. Once we check the local
857 stopped_start we'll know if we're in state (a) or (b) (see
858 CONCURRENCY NOTES above). */
859 if (stopped_start)
860 /* State (a), we own PD. The thread blocked on this lock either
861 because we're doing TD_CREATE event reporting, or for some
862 other reason that create_thread chose. Now let it run
863 free. */
864 lll_unlock (pd->lock, LLL_PRIVATE);
865
866 /* We now have for sure more than one thread. The main thread might
867 not yet have the flag set. No need to set the global variable
868 again if this is what we use. */
869 THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
870 }
871
872 out:
873 if (__glibc_unlikely (free_cpuset))
874 free (default_attr.cpuset);
875
876 return retval;
877}
878versioned_symbol (libpthread, __pthread_create_2_1, pthread_create, GLIBC_2_1);
879
880
881#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_1)
882int
883__pthread_create_2_0 (pthread_t *newthread, const pthread_attr_t *attr,
884 void *(*start_routine) (void *), void *arg)
885{
886 /* The ATTR attribute is not really of type `pthread_attr_t *'. It has
887 the old size and access to the new members might crash the program.
888 We convert the struct now. */
889 struct pthread_attr new_attr;
890
891 if (attr != NULL)
892 {
893 struct pthread_attr *iattr = (struct pthread_attr *) attr;
894 size_t ps = __getpagesize ();
895
896 /* Copy values from the user-provided attributes. */
897 new_attr.schedparam = iattr->schedparam;
898 new_attr.schedpolicy = iattr->schedpolicy;
899 new_attr.flags = iattr->flags;
900
901 /* Fill in default values for the fields not present in the old
902 implementation. */
903 new_attr.guardsize = ps;
904 new_attr.stackaddr = NULL;
905 new_attr.stacksize = 0;
906 new_attr.cpuset = NULL;
907
908 /* We will pass this value on to the real implementation. */
909 attr = (pthread_attr_t *) &new_attr;
910 }
911
912 return __pthread_create_2_1 (newthread, attr, start_routine, arg);
913}
914compat_symbol (libpthread, __pthread_create_2_0, pthread_create,
915 GLIBC_2_0);
916#endif
917
918/* Information for libthread_db. */
919
920#include "../nptl_db/db_info.c"
921
922/* If pthread_create is present, libgcc_eh.a and libsupc++.a expects some other POSIX thread
923 functions to be present as well. */
924PTHREAD_STATIC_FN_REQUIRE (__pthread_mutex_lock)
925PTHREAD_STATIC_FN_REQUIRE (__pthread_mutex_trylock)
926PTHREAD_STATIC_FN_REQUIRE (__pthread_mutex_unlock)
927
928PTHREAD_STATIC_FN_REQUIRE (__pthread_once)
929PTHREAD_STATIC_FN_REQUIRE (__pthread_cancel)
930
931PTHREAD_STATIC_FN_REQUIRE (__pthread_key_create)
932PTHREAD_STATIC_FN_REQUIRE (__pthread_key_delete)
933PTHREAD_STATIC_FN_REQUIRE (__pthread_setspecific)
934PTHREAD_STATIC_FN_REQUIRE (__pthread_getspecific)
935