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>
25 #include <sys/prctl.h>
28 #include <sys/types.h>
34 #include <semaphore.h>
38 #include <urcu/uatomic.h>
39 #include <urcu/futex.h>
40 #include <urcu/compiler.h>
42 #include <lttng/ust-events.h>
43 #include <lttng/ust-abi.h>
44 #include <lttng/ust.h>
46 #include <usterr-signal-safe.h>
47 #include "tracepoint-internal.h"
48 #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
)
188 uint32_t bits_per_long
;
189 char name
[16]; /* process name */
192 reg_msg
.major
= LTTNG_UST_COMM_VERSION_MAJOR
;
193 reg_msg
.minor
= LTTNG_UST_COMM_VERSION_MINOR
;
194 reg_msg
.pid
= getpid();
195 reg_msg
.ppid
= getppid();
196 reg_msg
.uid
= getuid();
197 reg_msg
.gid
= getgid();
198 reg_msg
.bits_per_long
= CAA_BITS_PER_LONG
;
199 prctl_ret
= prctl(PR_GET_NAME
, (unsigned long) reg_msg
.name
, 0, 0, 0);
201 ERR("Error executing prctl");
205 ret
= ustcomm_send_unix_sock(socket
, ®_msg
, sizeof(reg_msg
));
206 if (ret
>= 0 && ret
!= sizeof(reg_msg
))
212 int send_reply(int sock
, struct ustcomm_ust_reply
*lur
)
216 len
= ustcomm_send_unix_sock(sock
, lur
, sizeof(*lur
));
219 DBG("message successfully sent");
222 if (errno
== ECONNRESET
) {
223 printf("remote end closed connection\n");
228 printf("incorrect message size: %zd\n", len
);
234 int handle_register_done(struct sock_info
*sock_info
)
238 if (sock_info
->constructor_sem_posted
)
240 sock_info
->constructor_sem_posted
= 1;
241 if (uatomic_read(&sem_count
) <= 0) {
244 ret
= uatomic_add_return(&sem_count
, -1);
246 ret
= sem_post(&constructor_wait
);
253 int handle_message(struct sock_info
*sock_info
,
254 int sock
, struct ustcomm_ust_msg
*lum
)
257 const struct lttng_ust_objd_ops
*ops
;
258 struct ustcomm_ust_reply lur
;
264 memset(&lur
, 0, sizeof(lur
));
266 if (lttng_ust_comm_should_quit
) {
271 ops
= objd_ops(lum
->handle
);
278 case LTTNG_UST_REGISTER_DONE
:
279 if (lum
->handle
== LTTNG_UST_ROOT_HANDLE
)
280 ret
= handle_register_done(sock_info
);
284 case LTTNG_UST_RELEASE
:
285 if (lum
->handle
== LTTNG_UST_ROOT_HANDLE
)
288 ret
= lttng_ust_objd_unref(lum
->handle
);
292 ret
= ops
->cmd(lum
->handle
, lum
->cmd
,
293 (unsigned long) &lum
->u
,
301 lur
.handle
= lum
->handle
;
305 lur
.ret_code
= USTCOMM_OK
;
307 //lur.ret_code = USTCOMM_SESSION_FAIL;
312 case LTTNG_UST_STREAM
:
314 * Special-case reply to send stream info.
317 lur
.u
.stream
.memory_map_size
= *args
.stream
.memory_map_size
;
318 shm_fd
= *args
.stream
.shm_fd
;
319 wait_fd
= *args
.stream
.wait_fd
;
321 case LTTNG_UST_METADATA
:
322 case LTTNG_UST_CHANNEL
:
323 lur
.u
.channel
.memory_map_size
= *args
.channel
.memory_map_size
;
324 shm_fd
= *args
.channel
.shm_fd
;
325 wait_fd
= *args
.channel
.wait_fd
;
327 case LTTNG_UST_TRACER_VERSION
:
328 lur
.u
.version
= lum
->u
.version
;
330 case LTTNG_UST_TRACEPOINT_LIST_GET
:
331 memcpy(&lur
.u
.tracepoint
, &lum
->u
.tracepoint
, sizeof(lur
.u
.tracepoint
));
335 ret
= send_reply(sock
, &lur
);
337 perror("error sending reply");
341 if ((lum
->cmd
== LTTNG_UST_STREAM
342 || lum
->cmd
== LTTNG_UST_CHANNEL
343 || lum
->cmd
== LTTNG_UST_METADATA
)
344 && lur
.ret_code
== USTCOMM_OK
) {
347 /* we also need to send the file descriptors. */
348 ret
= ustcomm_send_fds_unix_sock(sock
,
352 perror("send shm_fd");
356 * The sessiond expects 2 file descriptors, even upon
359 ret
= ustcomm_send_fds_unix_sock(sock
,
363 perror("send wait_fd");
372 * We still have the memory map reference, and the fds have been
373 * sent to the sessiond. We can therefore close those fds. Note
374 * that we keep the write side of the wait_fd open, but close
377 if (lur
.ret_code
== USTCOMM_OK
) {
379 case LTTNG_UST_STREAM
:
383 PERROR("Error closing stream shm_fd");
385 *args
.stream
.shm_fd
= -1;
388 ret
= close(wait_fd
);
390 PERROR("Error closing stream wait_fd");
392 *args
.stream
.wait_fd
= -1;
395 case LTTNG_UST_METADATA
:
396 case LTTNG_UST_CHANNEL
:
400 PERROR("Error closing channel shm_fd");
402 *args
.channel
.shm_fd
= -1;
405 ret
= close(wait_fd
);
407 PERROR("Error closing channel wait_fd");
409 *args
.channel
.wait_fd
= -1;
421 void cleanup_sock_info(struct sock_info
*sock_info
, int exiting
)
425 if (sock_info
->socket
!= -1) {
426 ret
= ustcomm_close_unix_sock(sock_info
->socket
);
428 ERR("Error closing apps socket");
430 sock_info
->socket
= -1;
432 if (sock_info
->root_handle
!= -1) {
433 ret
= lttng_ust_objd_unref(sock_info
->root_handle
);
435 ERR("Error unref root handle");
437 sock_info
->root_handle
= -1;
439 sock_info
->constructor_sem_posted
= 0;
441 * wait_shm_mmap is used by listener threads outside of the
442 * ust lock, so we cannot tear it down ourselves, because we
443 * cannot join on these threads. Leave this task to the OS
446 if (!exiting
&& sock_info
->wait_shm_mmap
) {
447 ret
= munmap(sock_info
->wait_shm_mmap
, sysconf(_SC_PAGE_SIZE
));
449 ERR("Error unmapping wait shm");
451 sock_info
->wait_shm_mmap
= NULL
;
456 * Using fork to set umask in the child process (not multi-thread safe).
457 * We deal with the shm_open vs ftruncate race (happening when the
458 * sessiond owns the shm and does not let everybody modify it, to ensure
459 * safety against shm_unlink) by simply letting the mmap fail and
460 * retrying after a few seconds.
461 * For global shm, everybody has rw access to it until the sessiond
465 int get_wait_shm(struct sock_info
*sock_info
, size_t mmap_size
)
467 int wait_shm_fd
, ret
;
471 * Try to open read-only.
473 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
, O_RDONLY
, 0);
474 if (wait_shm_fd
>= 0) {
476 } else if (wait_shm_fd
< 0 && errno
!= ENOENT
) {
478 * Real-only open did not work, and it's not because the
479 * entry was not present. It's a failure that prohibits
482 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
486 * If the open failed because the file did not exist, try
487 * creating it ourself.
489 lttng_ust_nest_count
++;
491 lttng_ust_nest_count
--;
496 * Parent: wait for child to return, in which case the
497 * shared memory map will have been created.
500 if (pid
< 0 || !WIFEXITED(status
) || WEXITSTATUS(status
) != 0) {
505 * Try to open read-only again after creation.
507 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
, O_RDONLY
, 0);
508 if (wait_shm_fd
< 0) {
510 * Real-only open did not work. It's a failure
511 * that prohibits using shm.
513 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
517 } else if (pid
== 0) {
521 create_mode
= S_IRUSR
| S_IWUSR
| S_IRGRP
;
522 if (sock_info
->global
)
523 create_mode
|= S_IROTH
| S_IWGRP
| S_IWOTH
;
525 * We're alone in a child process, so we can modify the
526 * process-wide umask.
530 * Try creating shm (or get rw access).
531 * We don't do an exclusive open, because we allow other
532 * processes to create+ftruncate it concurrently.
534 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
,
535 O_RDWR
| O_CREAT
, create_mode
);
536 if (wait_shm_fd
>= 0) {
537 ret
= ftruncate(wait_shm_fd
, mmap_size
);
545 * For local shm, we need to have rw access to accept
546 * opening it: this means the local sessiond will be
547 * able to wake us up. For global shm, we open it even
548 * if rw access is not granted, because the root.root
549 * sessiond will be able to override all rights and wake
552 if (!sock_info
->global
&& errno
!= EACCES
) {
553 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
557 * The shm exists, but we cannot open it RW. Report
565 if (wait_shm_fd
>= 0 && !sock_info
->global
) {
569 * Ensure that our user is the owner of the shm file for
570 * local shm. If we do not own the file, it means our
571 * sessiond will not have access to wake us up (there is
572 * probably a rogue process trying to fake our
573 * sessiond). Fallback to polling method in this case.
575 ret
= fstat(wait_shm_fd
, &statbuf
);
580 if (statbuf
.st_uid
!= getuid())
586 ret
= close(wait_shm_fd
);
588 PERROR("Error closing fd");
594 char *get_map_shm(struct sock_info
*sock_info
)
596 size_t mmap_size
= sysconf(_SC_PAGE_SIZE
);
597 int wait_shm_fd
, ret
;
600 wait_shm_fd
= get_wait_shm(sock_info
, mmap_size
);
601 if (wait_shm_fd
< 0) {
604 wait_shm_mmap
= mmap(NULL
, mmap_size
, PROT_READ
,
605 MAP_SHARED
, wait_shm_fd
, 0);
606 /* close shm fd immediately after taking the mmap reference */
607 ret
= close(wait_shm_fd
);
609 PERROR("Error closing fd");
611 if (wait_shm_mmap
== MAP_FAILED
) {
612 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
615 return wait_shm_mmap
;
622 void wait_for_sessiond(struct sock_info
*sock_info
)
627 if (lttng_ust_comm_should_quit
) {
630 if (wait_poll_fallback
) {
633 if (!sock_info
->wait_shm_mmap
) {
634 sock_info
->wait_shm_mmap
= get_map_shm(sock_info
);
635 if (!sock_info
->wait_shm_mmap
)
640 DBG("Waiting for %s apps sessiond", sock_info
->name
);
641 /* Wait for futex wakeup */
642 if (uatomic_read((int32_t *) sock_info
->wait_shm_mmap
) == 0) {
643 ret
= futex_async((int32_t *) sock_info
->wait_shm_mmap
,
644 FUTEX_WAIT
, 0, NULL
, NULL
, 0);
646 if (errno
== EFAULT
) {
647 wait_poll_fallback
= 1;
649 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
650 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
651 "Please upgrade your kernel "
652 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
653 "mainline). LTTng-UST will use polling mode fallback.");
671 * This thread does not allocate any resource, except within
672 * handle_message, within mutex protection. This mutex protects against
674 * The other moment it allocates resources is at socket connexion, which
675 * is also protected by the mutex.
678 void *ust_listener_thread(void *arg
)
680 struct sock_info
*sock_info
= arg
;
681 int sock
, ret
, prev_connect_failed
= 0, has_waited
= 0;
683 /* Restart trying to connect to the session daemon */
685 if (prev_connect_failed
) {
686 /* Wait for sessiond availability with pipe */
687 wait_for_sessiond(sock_info
);
691 * Sleep for 5 seconds before retrying after a
692 * sequence of failure / wait / failure. This
693 * deals with a killed or broken session daemon.
698 prev_connect_failed
= 0;
702 if (lttng_ust_comm_should_quit
) {
707 if (sock_info
->socket
!= -1) {
708 ret
= ustcomm_close_unix_sock(sock_info
->socket
);
710 ERR("Error closing %s apps socket", sock_info
->name
);
712 sock_info
->socket
= -1;
716 ret
= ustcomm_connect_unix_sock(sock_info
->sock_path
);
718 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info
->name
);
719 prev_connect_failed
= 1;
721 * If we cannot find the sessiond daemon, don't delay
722 * constructor execution.
724 ret
= handle_register_done(sock_info
);
730 sock_info
->socket
= sock
= ret
;
733 * Create only one root handle per listener thread for the whole
736 if (sock_info
->root_handle
== -1) {
737 ret
= lttng_abi_create_root_handle();
739 ERR("Error creating root handle");
743 sock_info
->root_handle
= ret
;
746 ret
= register_app_to_sessiond(sock
);
748 ERR("Error registering to %s apps socket", sock_info
->name
);
749 prev_connect_failed
= 1;
751 * If we cannot register to the sessiond daemon, don't
752 * delay constructor execution.
754 ret
= handle_register_done(sock_info
);
763 struct ustcomm_ust_msg lum
;
765 len
= ustcomm_recv_unix_sock(sock
, &lum
, sizeof(lum
));
767 case 0: /* orderly shutdown */
768 DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info
->name
);
771 * Either sessiond has shutdown or refused us by closing the socket.
772 * In either case, we don't want to delay construction execution,
773 * and we need to wait before retry.
775 prev_connect_failed
= 1;
777 * If we cannot register to the sessiond daemon, don't
778 * delay constructor execution.
780 ret
= handle_register_done(sock_info
);
785 DBG("message received\n");
786 ret
= handle_message(sock_info
, sock
, &lum
);
788 ERR("Error handling message for %s socket", sock_info
->name
);
792 DBG("Receive failed from lttng-sessiond with errno %d", errno
);
793 if (errno
== ECONNRESET
) {
794 ERR("%s remote end closed connection\n", sock_info
->name
);
799 ERR("incorrect message size (%s socket): %zd\n", sock_info
->name
, len
);
805 goto restart
; /* try to reconnect */
811 * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
814 int get_timeout(struct timespec
*constructor_timeout
)
816 long constructor_delay_ms
= LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS
;
820 str_delay
= getenv("LTTNG_UST_REGISTER_TIMEOUT");
822 constructor_delay_ms
= strtol(str_delay
, NULL
, 10);
825 switch (constructor_delay_ms
) {
826 case -1:/* fall-through */
828 return constructor_delay_ms
;
834 * If we are unable to find the current time, don't wait.
836 ret
= clock_gettime(CLOCK_REALTIME
, constructor_timeout
);
840 constructor_timeout
->tv_sec
+= constructor_delay_ms
/ 1000UL;
841 constructor_timeout
->tv_nsec
+=
842 (constructor_delay_ms
% 1000UL) * 1000000UL;
843 if (constructor_timeout
->tv_nsec
>= 1000000000UL) {
844 constructor_timeout
->tv_sec
++;
845 constructor_timeout
->tv_nsec
-= 1000000000UL;
851 * sessiond monitoring thread: monitor presence of global and per-user
852 * sessiond by polling the application common named pipe.
856 void __attribute__((constructor
)) lttng_ust_init(void)
858 struct timespec constructor_timeout
;
859 sigset_t sig_all_blocked
, orig_parent_mask
;
860 pthread_attr_t thread_attr
;
864 if (uatomic_xchg(&initialized
, 1) == 1)
868 * Fixup interdependency between TLS fixup mutex (which happens
869 * to be the dynamic linker mutex) and ust_lock, taken within
872 lttng_fixup_event_tls();
873 lttng_fixup_ringbuffer_tls();
874 lttng_fixup_vtid_tls();
875 lttng_fixup_nest_count_tls();
878 * We want precise control over the order in which we construct
879 * our sub-libraries vs starting to receive commands from
880 * sessiond (otherwise leading to errors when trying to create
881 * sessiond before the init functions are completed).
885 ltt_ring_buffer_metadata_client_init();
886 ltt_ring_buffer_client_overwrite_init();
887 ltt_ring_buffer_client_discard_init();
889 timeout_mode
= get_timeout(&constructor_timeout
);
891 ret
= sem_init(&constructor_wait
, 0, 0);
894 ret
= setup_local_apps();
896 DBG("local apps setup returned %d", ret
);
899 /* A new thread created by pthread_create inherits the signal mask
900 * from the parent. To avoid any signal being received by the
901 * listener thread, we block all signals temporarily in the parent,
902 * while we create the listener thread.
904 sigfillset(&sig_all_blocked
);
905 ret
= pthread_sigmask(SIG_SETMASK
, &sig_all_blocked
, &orig_parent_mask
);
907 ERR("pthread_sigmask: %s", strerror(ret
));
910 ret
= pthread_attr_init(&thread_attr
);
912 ERR("pthread_attr_init: %s", strerror(ret
));
914 ret
= pthread_attr_setdetachstate(&thread_attr
, PTHREAD_CREATE_DETACHED
);
916 ERR("pthread_attr_setdetachstate: %s", strerror(ret
));
919 ret
= pthread_create(&global_apps
.ust_listener
, &thread_attr
,
920 ust_listener_thread
, &global_apps
);
922 ERR("pthread_create global: %s", strerror(ret
));
924 if (local_apps
.allowed
) {
925 ret
= pthread_create(&local_apps
.ust_listener
, &thread_attr
,
926 ust_listener_thread
, &local_apps
);
928 ERR("pthread_create local: %s", strerror(ret
));
931 handle_register_done(&local_apps
);
933 ret
= pthread_attr_destroy(&thread_attr
);
935 ERR("pthread_attr_destroy: %s", strerror(ret
));
938 /* Restore original signal mask in parent */
939 ret
= pthread_sigmask(SIG_SETMASK
, &orig_parent_mask
, NULL
);
941 ERR("pthread_sigmask: %s", strerror(ret
));
944 switch (timeout_mode
) {
945 case 1: /* timeout wait */
947 ret
= sem_timedwait(&constructor_wait
,
948 &constructor_timeout
);
949 } while (ret
< 0 && errno
== EINTR
);
950 if (ret
< 0 && errno
== ETIMEDOUT
) {
951 ERR("Timed out waiting for ltt-sessiond");
956 case -1:/* wait forever */
958 ret
= sem_wait(&constructor_wait
);
959 } while (ret
< 0 && errno
== EINTR
);
962 case 0: /* no timeout */
968 void lttng_ust_cleanup(int exiting
)
970 cleanup_sock_info(&global_apps
, exiting
);
971 if (local_apps
.allowed
) {
972 cleanup_sock_info(&local_apps
, exiting
);
975 * The teardown in this function all affect data structures
976 * accessed under the UST lock by the listener thread. This
977 * lock, along with the lttng_ust_comm_should_quit flag, ensure
978 * that none of these threads are accessing this data at this
981 lttng_ust_abi_exit();
982 lttng_ust_events_exit();
983 ltt_ring_buffer_client_discard_exit();
984 ltt_ring_buffer_client_overwrite_exit();
985 ltt_ring_buffer_metadata_client_exit();
988 /* Reinitialize values for fork */
990 lttng_ust_comm_should_quit
= 0;
995 void __attribute__((destructor
)) lttng_ust_exit(void)
1000 * Using pthread_cancel here because:
1001 * A) we don't want to hang application teardown.
1002 * B) the thread is not allocating any resource.
1006 * Require the communication thread to quit. Synchronize with
1007 * mutexes to ensure it is not in a mutex critical section when
1008 * pthread_cancel is later called.
1011 lttng_ust_comm_should_quit
= 1;
1014 /* cancel threads */
1015 ret
= pthread_cancel(global_apps
.ust_listener
);
1017 ERR("Error cancelling global ust listener thread: %s",
1020 if (local_apps
.allowed
) {
1021 ret
= pthread_cancel(local_apps
.ust_listener
);
1023 ERR("Error cancelling local ust listener thread: %s",
1028 * Do NOT join threads: use of sys_futex makes it impossible to
1029 * join the threads without using async-cancel, but async-cancel
1030 * is delivered by a signal, which could hit the target thread
1031 * anywhere in its code path, including while the ust_lock() is
1032 * held, causing a deadlock for the other thread. Let the OS
1033 * cleanup the threads if there are stalled in a syscall.
1035 lttng_ust_cleanup(1);
1039 * We exclude the worker threads across fork and clone (except
1040 * CLONE_VM), because these system calls only keep the forking thread
1041 * running in the child. Therefore, we don't want to call fork or clone
1042 * in the middle of an tracepoint or ust tracing state modification.
1043 * Holding this mutex protects these structures across fork and clone.
1045 void ust_before_fork(sigset_t
*save_sigset
)
1048 * Disable signals. This is to avoid that the child intervenes
1049 * before it is properly setup for tracing. It is safer to
1050 * disable all signals, because then we know we are not breaking
1051 * anything by restoring the original mask.
1056 if (lttng_ust_nest_count
)
1058 /* Disable signals */
1059 sigfillset(&all_sigs
);
1060 ret
= sigprocmask(SIG_BLOCK
, &all_sigs
, save_sigset
);
1062 PERROR("sigprocmask");
1065 rcu_bp_before_fork();
1068 static void ust_after_fork_common(sigset_t
*restore_sigset
)
1072 DBG("process %d", getpid());
1074 /* Restore signals */
1075 ret
= sigprocmask(SIG_SETMASK
, restore_sigset
, NULL
);
1077 PERROR("sigprocmask");
1081 void ust_after_fork_parent(sigset_t
*restore_sigset
)
1083 if (lttng_ust_nest_count
)
1085 DBG("process %d", getpid());
1086 rcu_bp_after_fork_parent();
1087 /* Release mutexes and reenable signals */
1088 ust_after_fork_common(restore_sigset
);
1092 * After fork, in the child, we need to cleanup all the leftover state,
1093 * except the worker thread which already magically disappeared thanks
1094 * to the weird Linux fork semantics. After tyding up, we call
1095 * lttng_ust_init() again to start over as a new PID.
1097 * This is meant for forks() that have tracing in the child between the
1098 * fork and following exec call (if there is any).
1100 void ust_after_fork_child(sigset_t
*restore_sigset
)
1102 if (lttng_ust_nest_count
)
1104 DBG("process %d", getpid());
1105 /* Release urcu mutexes */
1106 rcu_bp_after_fork_child();
1107 lttng_ust_cleanup(0);
1108 lttng_context_vtid_reset();
1109 /* Release mutexes and reenable signals */
1110 ust_after_fork_common(restore_sigset
);