4 * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
5 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; only
10 * version 2.1 of the License.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this library; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 #include <sys/types.h>
24 #include <sys/socket.h>
27 #include <sys/types.h>
33 #include <semaphore.h>
37 #include <urcu/uatomic.h>
38 #include <urcu/futex.h>
39 #include <urcu/compiler.h>
41 #include <lttng/ust-events.h>
42 #include <lttng/ust-abi.h>
43 #include <lttng/ust.h>
45 #include <usterr-signal-safe.h>
46 #include "tracepoint-internal.h"
47 #include "ltt-tracer-core.h"
49 #include "../libringbuffer/tlsfixup.h"
52 * Has lttng ust comm constructor been called ?
54 static int initialized
;
57 * The ust_lock/ust_unlock lock is used as a communication thread mutex.
58 * Held when handling a command, also held by fork() to deal with
59 * removal of threads, and by exit path.
62 /* Should the ust comm thread quit ? */
63 static int lttng_ust_comm_should_quit
;
66 * Wait for either of these before continuing to the main
68 * - the register_done message from sessiond daemon
69 * (will let the sessiond daemon enable sessions before main
71 * - sessiond daemon is not reachable.
72 * - timeout (ensuring applications are resilient to session
75 static sem_t constructor_wait
;
77 * Doing this for both the global and local sessiond.
79 static int sem_count
= { 2 };
82 * Counting nesting within lttng-ust. Used to ensure that calling fork()
83 * from liblttng-ust does not execute the pre/post fork handlers.
85 static int __thread lttng_ust_nest_count
;
88 * Info about socket and associated listener thread.
92 pthread_t ust_listener
; /* listener thread */
94 int constructor_sem_posted
;
98 char sock_path
[PATH_MAX
];
101 char wait_shm_path
[PATH_MAX
];
105 /* Socket from app (connect) to session daemon (listen) for communication */
106 struct sock_info global_apps
= {
113 .sock_path
= DEFAULT_GLOBAL_APPS_UNIX_SOCK
,
116 .wait_shm_path
= DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH
,
119 /* TODO: allow global_apps_sock_path override */
121 struct sock_info local_apps
= {
125 .allowed
= 0, /* Check setuid bit first */
130 static int wait_poll_fallback
;
132 extern void ltt_ring_buffer_client_overwrite_init(void);
133 extern void ltt_ring_buffer_client_discard_init(void);
134 extern void ltt_ring_buffer_metadata_client_init(void);
135 extern void ltt_ring_buffer_client_overwrite_exit(void);
136 extern void ltt_ring_buffer_client_discard_exit(void);
137 extern void ltt_ring_buffer_metadata_client_exit(void);
140 * Force a read (imply TLS fixup for dlopen) of TLS variables.
143 void lttng_fixup_nest_count_tls(void)
145 asm volatile ("" : : "m" (lttng_ust_nest_count
));
149 int setup_local_apps(void)
151 const char *home_dir
;
156 * Disallow per-user tracing for setuid binaries.
158 if (uid
!= geteuid()) {
159 assert(local_apps
.allowed
== 0);
162 home_dir
= (const char *) getenv("HOME");
164 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
165 assert(local_apps
.allowed
== 0);
168 local_apps
.allowed
= 1;
169 snprintf(local_apps
.sock_path
, PATH_MAX
,
170 DEFAULT_HOME_APPS_UNIX_SOCK
, home_dir
);
171 snprintf(local_apps
.wait_shm_path
, PATH_MAX
,
172 DEFAULT_HOME_APPS_WAIT_SHM_PATH
, uid
);
177 int register_app_to_sessiond(int socket
)
187 uint32_t bits_per_long
;
188 char name
[16]; /* process name */
191 reg_msg
.major
= LTTNG_UST_COMM_VERSION_MAJOR
;
192 reg_msg
.minor
= LTTNG_UST_COMM_VERSION_MINOR
;
193 reg_msg
.pid
= getpid();
194 reg_msg
.ppid
= getppid();
195 reg_msg
.uid
= getuid();
196 reg_msg
.gid
= getgid();
197 reg_msg
.bits_per_long
= CAA_BITS_PER_LONG
;
198 lttng_ust_getprocname(reg_msg
.name
);
200 ret
= ustcomm_send_unix_sock(socket
, ®_msg
, sizeof(reg_msg
));
201 if (ret
>= 0 && ret
!= sizeof(reg_msg
))
207 int send_reply(int sock
, struct ustcomm_ust_reply
*lur
)
211 len
= ustcomm_send_unix_sock(sock
, lur
, sizeof(*lur
));
214 DBG("message successfully sent");
217 if (errno
== ECONNRESET
) {
218 printf("remote end closed connection\n");
223 printf("incorrect message size: %zd\n", len
);
229 int handle_register_done(struct sock_info
*sock_info
)
233 if (sock_info
->constructor_sem_posted
)
235 sock_info
->constructor_sem_posted
= 1;
236 if (uatomic_read(&sem_count
) <= 0) {
239 ret
= uatomic_add_return(&sem_count
, -1);
241 ret
= sem_post(&constructor_wait
);
248 int handle_message(struct sock_info
*sock_info
,
249 int sock
, struct ustcomm_ust_msg
*lum
)
252 const struct lttng_ust_objd_ops
*ops
;
253 struct ustcomm_ust_reply lur
;
259 memset(&lur
, 0, sizeof(lur
));
261 if (lttng_ust_comm_should_quit
) {
266 ops
= objd_ops(lum
->handle
);
273 case LTTNG_UST_REGISTER_DONE
:
274 if (lum
->handle
== LTTNG_UST_ROOT_HANDLE
)
275 ret
= handle_register_done(sock_info
);
279 case LTTNG_UST_RELEASE
:
280 if (lum
->handle
== LTTNG_UST_ROOT_HANDLE
)
283 ret
= lttng_ust_objd_unref(lum
->handle
);
287 ret
= ops
->cmd(lum
->handle
, lum
->cmd
,
288 (unsigned long) &lum
->u
,
296 lur
.handle
= lum
->handle
;
300 lur
.ret_code
= USTCOMM_OK
;
302 //lur.ret_code = USTCOMM_SESSION_FAIL;
307 case LTTNG_UST_STREAM
:
309 * Special-case reply to send stream info.
312 lur
.u
.stream
.memory_map_size
= *args
.stream
.memory_map_size
;
313 shm_fd
= *args
.stream
.shm_fd
;
314 wait_fd
= *args
.stream
.wait_fd
;
316 case LTTNG_UST_METADATA
:
317 case LTTNG_UST_CHANNEL
:
318 lur
.u
.channel
.memory_map_size
= *args
.channel
.memory_map_size
;
319 shm_fd
= *args
.channel
.shm_fd
;
320 wait_fd
= *args
.channel
.wait_fd
;
322 case LTTNG_UST_TRACER_VERSION
:
323 lur
.u
.version
= lum
->u
.version
;
325 case LTTNG_UST_TRACEPOINT_LIST_GET
:
326 memcpy(&lur
.u
.tracepoint
, &lum
->u
.tracepoint
, sizeof(lur
.u
.tracepoint
));
330 ret
= send_reply(sock
, &lur
);
332 perror("error sending reply");
336 if ((lum
->cmd
== LTTNG_UST_STREAM
337 || lum
->cmd
== LTTNG_UST_CHANNEL
338 || lum
->cmd
== LTTNG_UST_METADATA
)
339 && lur
.ret_code
== USTCOMM_OK
) {
342 /* we also need to send the file descriptors. */
343 ret
= ustcomm_send_fds_unix_sock(sock
,
347 perror("send shm_fd");
351 * The sessiond expects 2 file descriptors, even upon
354 ret
= ustcomm_send_fds_unix_sock(sock
,
358 perror("send wait_fd");
367 * We still have the memory map reference, and the fds have been
368 * sent to the sessiond. We can therefore close those fds. Note
369 * that we keep the write side of the wait_fd open, but close
372 if (lur
.ret_code
== USTCOMM_OK
) {
374 case LTTNG_UST_STREAM
:
378 PERROR("Error closing stream shm_fd");
380 *args
.stream
.shm_fd
= -1;
383 ret
= close(wait_fd
);
385 PERROR("Error closing stream wait_fd");
387 *args
.stream
.wait_fd
= -1;
390 case LTTNG_UST_METADATA
:
391 case LTTNG_UST_CHANNEL
:
395 PERROR("Error closing channel shm_fd");
397 *args
.channel
.shm_fd
= -1;
400 ret
= close(wait_fd
);
402 PERROR("Error closing channel wait_fd");
404 *args
.channel
.wait_fd
= -1;
416 void cleanup_sock_info(struct sock_info
*sock_info
, int exiting
)
420 if (sock_info
->socket
!= -1) {
421 ret
= ustcomm_close_unix_sock(sock_info
->socket
);
423 ERR("Error closing apps socket");
425 sock_info
->socket
= -1;
427 if (sock_info
->root_handle
!= -1) {
428 ret
= lttng_ust_objd_unref(sock_info
->root_handle
);
430 ERR("Error unref root handle");
432 sock_info
->root_handle
= -1;
434 sock_info
->constructor_sem_posted
= 0;
436 * wait_shm_mmap is used by listener threads outside of the
437 * ust lock, so we cannot tear it down ourselves, because we
438 * cannot join on these threads. Leave this task to the OS
441 if (!exiting
&& sock_info
->wait_shm_mmap
) {
442 ret
= munmap(sock_info
->wait_shm_mmap
, sysconf(_SC_PAGE_SIZE
));
444 ERR("Error unmapping wait shm");
446 sock_info
->wait_shm_mmap
= NULL
;
451 * Using fork to set umask in the child process (not multi-thread safe).
452 * We deal with the shm_open vs ftruncate race (happening when the
453 * sessiond owns the shm and does not let everybody modify it, to ensure
454 * safety against shm_unlink) by simply letting the mmap fail and
455 * retrying after a few seconds.
456 * For global shm, everybody has rw access to it until the sessiond
460 int get_wait_shm(struct sock_info
*sock_info
, size_t mmap_size
)
462 int wait_shm_fd
, ret
;
466 * Try to open read-only.
468 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
, O_RDONLY
, 0);
469 if (wait_shm_fd
>= 0) {
471 } else if (wait_shm_fd
< 0 && errno
!= ENOENT
) {
473 * Real-only open did not work, and it's not because the
474 * entry was not present. It's a failure that prohibits
477 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
481 * If the open failed because the file did not exist, try
482 * creating it ourself.
484 lttng_ust_nest_count
++;
486 lttng_ust_nest_count
--;
491 * Parent: wait for child to return, in which case the
492 * shared memory map will have been created.
495 if (pid
< 0 || !WIFEXITED(status
) || WEXITSTATUS(status
) != 0) {
500 * Try to open read-only again after creation.
502 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
, O_RDONLY
, 0);
503 if (wait_shm_fd
< 0) {
505 * Real-only open did not work. It's a failure
506 * that prohibits using shm.
508 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
512 } else if (pid
== 0) {
516 create_mode
= S_IRUSR
| S_IWUSR
| S_IRGRP
;
517 if (sock_info
->global
)
518 create_mode
|= S_IROTH
| S_IWGRP
| S_IWOTH
;
520 * We're alone in a child process, so we can modify the
521 * process-wide umask.
525 * Try creating shm (or get rw access).
526 * We don't do an exclusive open, because we allow other
527 * processes to create+ftruncate it concurrently.
529 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
,
530 O_RDWR
| O_CREAT
, create_mode
);
531 if (wait_shm_fd
>= 0) {
532 ret
= ftruncate(wait_shm_fd
, mmap_size
);
540 * For local shm, we need to have rw access to accept
541 * opening it: this means the local sessiond will be
542 * able to wake us up. For global shm, we open it even
543 * if rw access is not granted, because the root.root
544 * sessiond will be able to override all rights and wake
547 if (!sock_info
->global
&& errno
!= EACCES
) {
548 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
552 * The shm exists, but we cannot open it RW. Report
560 if (wait_shm_fd
>= 0 && !sock_info
->global
) {
564 * Ensure that our user is the owner of the shm file for
565 * local shm. If we do not own the file, it means our
566 * sessiond will not have access to wake us up (there is
567 * probably a rogue process trying to fake our
568 * sessiond). Fallback to polling method in this case.
570 ret
= fstat(wait_shm_fd
, &statbuf
);
575 if (statbuf
.st_uid
!= getuid())
581 ret
= close(wait_shm_fd
);
583 PERROR("Error closing fd");
589 char *get_map_shm(struct sock_info
*sock_info
)
591 size_t mmap_size
= sysconf(_SC_PAGE_SIZE
);
592 int wait_shm_fd
, ret
;
595 wait_shm_fd
= get_wait_shm(sock_info
, mmap_size
);
596 if (wait_shm_fd
< 0) {
599 wait_shm_mmap
= mmap(NULL
, mmap_size
, PROT_READ
,
600 MAP_SHARED
, wait_shm_fd
, 0);
601 /* close shm fd immediately after taking the mmap reference */
602 ret
= close(wait_shm_fd
);
604 PERROR("Error closing fd");
606 if (wait_shm_mmap
== MAP_FAILED
) {
607 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
610 return wait_shm_mmap
;
617 void wait_for_sessiond(struct sock_info
*sock_info
)
622 if (lttng_ust_comm_should_quit
) {
625 if (wait_poll_fallback
) {
628 if (!sock_info
->wait_shm_mmap
) {
629 sock_info
->wait_shm_mmap
= get_map_shm(sock_info
);
630 if (!sock_info
->wait_shm_mmap
)
635 DBG("Waiting for %s apps sessiond", sock_info
->name
);
636 /* Wait for futex wakeup */
637 if (uatomic_read((int32_t *) sock_info
->wait_shm_mmap
) == 0) {
638 ret
= futex_async((int32_t *) sock_info
->wait_shm_mmap
,
639 FUTEX_WAIT
, 0, NULL
, NULL
, 0);
641 if (errno
== EFAULT
) {
642 wait_poll_fallback
= 1;
644 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
645 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
646 "Please upgrade your kernel "
647 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
648 "mainline). LTTng-UST will use polling mode fallback.");
666 * This thread does not allocate any resource, except within
667 * handle_message, within mutex protection. This mutex protects against
669 * The other moment it allocates resources is at socket connexion, which
670 * is also protected by the mutex.
673 void *ust_listener_thread(void *arg
)
675 struct sock_info
*sock_info
= arg
;
676 int sock
, ret
, prev_connect_failed
= 0, has_waited
= 0;
678 /* Restart trying to connect to the session daemon */
680 if (prev_connect_failed
) {
681 /* Wait for sessiond availability with pipe */
682 wait_for_sessiond(sock_info
);
686 * Sleep for 5 seconds before retrying after a
687 * sequence of failure / wait / failure. This
688 * deals with a killed or broken session daemon.
693 prev_connect_failed
= 0;
697 if (lttng_ust_comm_should_quit
) {
702 if (sock_info
->socket
!= -1) {
703 ret
= ustcomm_close_unix_sock(sock_info
->socket
);
705 ERR("Error closing %s apps socket", sock_info
->name
);
707 sock_info
->socket
= -1;
711 ret
= ustcomm_connect_unix_sock(sock_info
->sock_path
);
713 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info
->name
);
714 prev_connect_failed
= 1;
716 * If we cannot find the sessiond daemon, don't delay
717 * constructor execution.
719 ret
= handle_register_done(sock_info
);
725 sock_info
->socket
= sock
= ret
;
728 * Create only one root handle per listener thread for the whole
731 if (sock_info
->root_handle
== -1) {
732 ret
= lttng_abi_create_root_handle();
734 ERR("Error creating root handle");
738 sock_info
->root_handle
= ret
;
741 ret
= register_app_to_sessiond(sock
);
743 ERR("Error registering to %s apps socket", sock_info
->name
);
744 prev_connect_failed
= 1;
746 * If we cannot register to the sessiond daemon, don't
747 * delay constructor execution.
749 ret
= handle_register_done(sock_info
);
758 struct ustcomm_ust_msg lum
;
760 len
= ustcomm_recv_unix_sock(sock
, &lum
, sizeof(lum
));
762 case 0: /* orderly shutdown */
763 DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info
->name
);
766 * Either sessiond has shutdown or refused us by closing the socket.
767 * In either case, we don't want to delay construction execution,
768 * and we need to wait before retry.
770 prev_connect_failed
= 1;
772 * If we cannot register to the sessiond daemon, don't
773 * delay constructor execution.
775 ret
= handle_register_done(sock_info
);
780 DBG("message received\n");
781 ret
= handle_message(sock_info
, sock
, &lum
);
783 ERR("Error handling message for %s socket", sock_info
->name
);
787 DBG("Receive failed from lttng-sessiond with errno %d", errno
);
788 if (errno
== ECONNRESET
) {
789 ERR("%s remote end closed connection\n", sock_info
->name
);
794 ERR("incorrect message size (%s socket): %zd\n", sock_info
->name
, len
);
800 goto restart
; /* try to reconnect */
806 * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
809 int get_timeout(struct timespec
*constructor_timeout
)
811 long constructor_delay_ms
= LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS
;
815 str_delay
= getenv("LTTNG_UST_REGISTER_TIMEOUT");
817 constructor_delay_ms
= strtol(str_delay
, NULL
, 10);
820 switch (constructor_delay_ms
) {
821 case -1:/* fall-through */
823 return constructor_delay_ms
;
829 * If we are unable to find the current time, don't wait.
831 ret
= clock_gettime(CLOCK_REALTIME
, constructor_timeout
);
835 constructor_timeout
->tv_sec
+= constructor_delay_ms
/ 1000UL;
836 constructor_timeout
->tv_nsec
+=
837 (constructor_delay_ms
% 1000UL) * 1000000UL;
838 if (constructor_timeout
->tv_nsec
>= 1000000000UL) {
839 constructor_timeout
->tv_sec
++;
840 constructor_timeout
->tv_nsec
-= 1000000000UL;
846 * sessiond monitoring thread: monitor presence of global and per-user
847 * sessiond by polling the application common named pipe.
851 void __attribute__((constructor
)) lttng_ust_init(void)
853 struct timespec constructor_timeout
;
854 sigset_t sig_all_blocked
, orig_parent_mask
;
855 pthread_attr_t thread_attr
;
859 if (uatomic_xchg(&initialized
, 1) == 1)
863 * Fixup interdependency between TLS fixup mutex (which happens
864 * to be the dynamic linker mutex) and ust_lock, taken within
867 lttng_fixup_event_tls();
868 lttng_fixup_ringbuffer_tls();
869 lttng_fixup_vtid_tls();
870 lttng_fixup_nest_count_tls();
873 * We want precise control over the order in which we construct
874 * our sub-libraries vs starting to receive commands from
875 * sessiond (otherwise leading to errors when trying to create
876 * sessiond before the init functions are completed).
880 ltt_ring_buffer_metadata_client_init();
881 ltt_ring_buffer_client_overwrite_init();
882 ltt_ring_buffer_client_discard_init();
884 timeout_mode
= get_timeout(&constructor_timeout
);
886 ret
= sem_init(&constructor_wait
, 0, 0);
889 ret
= setup_local_apps();
891 DBG("local apps setup returned %d", ret
);
894 /* A new thread created by pthread_create inherits the signal mask
895 * from the parent. To avoid any signal being received by the
896 * listener thread, we block all signals temporarily in the parent,
897 * while we create the listener thread.
899 sigfillset(&sig_all_blocked
);
900 ret
= pthread_sigmask(SIG_SETMASK
, &sig_all_blocked
, &orig_parent_mask
);
902 ERR("pthread_sigmask: %s", strerror(ret
));
905 ret
= pthread_attr_init(&thread_attr
);
907 ERR("pthread_attr_init: %s", strerror(ret
));
909 ret
= pthread_attr_setdetachstate(&thread_attr
, PTHREAD_CREATE_DETACHED
);
911 ERR("pthread_attr_setdetachstate: %s", strerror(ret
));
914 ret
= pthread_create(&global_apps
.ust_listener
, &thread_attr
,
915 ust_listener_thread
, &global_apps
);
917 ERR("pthread_create global: %s", strerror(ret
));
919 if (local_apps
.allowed
) {
920 ret
= pthread_create(&local_apps
.ust_listener
, &thread_attr
,
921 ust_listener_thread
, &local_apps
);
923 ERR("pthread_create local: %s", strerror(ret
));
926 handle_register_done(&local_apps
);
928 ret
= pthread_attr_destroy(&thread_attr
);
930 ERR("pthread_attr_destroy: %s", strerror(ret
));
933 /* Restore original signal mask in parent */
934 ret
= pthread_sigmask(SIG_SETMASK
, &orig_parent_mask
, NULL
);
936 ERR("pthread_sigmask: %s", strerror(ret
));
939 switch (timeout_mode
) {
940 case 1: /* timeout wait */
942 ret
= sem_timedwait(&constructor_wait
,
943 &constructor_timeout
);
944 } while (ret
< 0 && errno
== EINTR
);
945 if (ret
< 0 && errno
== ETIMEDOUT
) {
946 ERR("Timed out waiting for ltt-sessiond");
951 case -1:/* wait forever */
953 ret
= sem_wait(&constructor_wait
);
954 } while (ret
< 0 && errno
== EINTR
);
957 case 0: /* no timeout */
963 void lttng_ust_cleanup(int exiting
)
965 cleanup_sock_info(&global_apps
, exiting
);
966 if (local_apps
.allowed
) {
967 cleanup_sock_info(&local_apps
, exiting
);
970 * The teardown in this function all affect data structures
971 * accessed under the UST lock by the listener thread. This
972 * lock, along with the lttng_ust_comm_should_quit flag, ensure
973 * that none of these threads are accessing this data at this
976 lttng_ust_abi_exit();
977 lttng_ust_events_exit();
978 ltt_ring_buffer_client_discard_exit();
979 ltt_ring_buffer_client_overwrite_exit();
980 ltt_ring_buffer_metadata_client_exit();
983 /* Reinitialize values for fork */
985 lttng_ust_comm_should_quit
= 0;
990 void __attribute__((destructor
)) lttng_ust_exit(void)
995 * Using pthread_cancel here because:
996 * A) we don't want to hang application teardown.
997 * B) the thread is not allocating any resource.
1001 * Require the communication thread to quit. Synchronize with
1002 * mutexes to ensure it is not in a mutex critical section when
1003 * pthread_cancel is later called.
1006 lttng_ust_comm_should_quit
= 1;
1009 /* cancel threads */
1010 ret
= pthread_cancel(global_apps
.ust_listener
);
1012 ERR("Error cancelling global ust listener thread: %s",
1015 if (local_apps
.allowed
) {
1016 ret
= pthread_cancel(local_apps
.ust_listener
);
1018 ERR("Error cancelling local ust listener thread: %s",
1023 * Do NOT join threads: use of sys_futex makes it impossible to
1024 * join the threads without using async-cancel, but async-cancel
1025 * is delivered by a signal, which could hit the target thread
1026 * anywhere in its code path, including while the ust_lock() is
1027 * held, causing a deadlock for the other thread. Let the OS
1028 * cleanup the threads if there are stalled in a syscall.
1030 lttng_ust_cleanup(1);
1034 * We exclude the worker threads across fork and clone (except
1035 * CLONE_VM), because these system calls only keep the forking thread
1036 * running in the child. Therefore, we don't want to call fork or clone
1037 * in the middle of an tracepoint or ust tracing state modification.
1038 * Holding this mutex protects these structures across fork and clone.
1040 void ust_before_fork(sigset_t
*save_sigset
)
1043 * Disable signals. This is to avoid that the child intervenes
1044 * before it is properly setup for tracing. It is safer to
1045 * disable all signals, because then we know we are not breaking
1046 * anything by restoring the original mask.
1051 if (lttng_ust_nest_count
)
1053 /* Disable signals */
1054 sigfillset(&all_sigs
);
1055 ret
= sigprocmask(SIG_BLOCK
, &all_sigs
, save_sigset
);
1057 PERROR("sigprocmask");
1060 rcu_bp_before_fork();
1063 static void ust_after_fork_common(sigset_t
*restore_sigset
)
1067 DBG("process %d", getpid());
1069 /* Restore signals */
1070 ret
= sigprocmask(SIG_SETMASK
, restore_sigset
, NULL
);
1072 PERROR("sigprocmask");
1076 void ust_after_fork_parent(sigset_t
*restore_sigset
)
1078 if (lttng_ust_nest_count
)
1080 DBG("process %d", getpid());
1081 rcu_bp_after_fork_parent();
1082 /* Release mutexes and reenable signals */
1083 ust_after_fork_common(restore_sigset
);
1087 * After fork, in the child, we need to cleanup all the leftover state,
1088 * except the worker thread which already magically disappeared thanks
1089 * to the weird Linux fork semantics. After tyding up, we call
1090 * lttng_ust_init() again to start over as a new PID.
1092 * This is meant for forks() that have tracing in the child between the
1093 * fork and following exec call (if there is any).
1095 void ust_after_fork_child(sigset_t
*restore_sigset
)
1097 if (lttng_ust_nest_count
)
1099 DBG("process %d", getpid());
1100 /* Release urcu mutexes */
1101 rcu_bp_after_fork_child();
1102 lttng_ust_cleanup(0);
1103 lttng_context_vtid_reset();
1104 /* Release mutexes and reenable signals */
1105 ust_after_fork_common(restore_sigset
);