The select(2) system call is an ancient ABI limited to processes
containing at most FD_SETSIZE file descriptors overall (typically
1024).
This select call will fail if the target file descriptor is above
FD_SETSIZE in a session daemon containing many file descriptors.
This is unlikely to happen in normal use given than
sessiond_init_thread_quit_pipe() is called early by main(). Odd
scenarios could trigger this, for instance if the parent process leaves
a large number of file descriptors open, or if a library which
allocates file descriptors is LD_PRELOADed with the sessiond.
Never use select, use the lttng epoll/poll wrapper instead.
This patch depends on "Change lttng_poll_wait behaviour of compat-poll
to match compat-epoll" posted by Yannick Lamarre.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
CC: Yannick Lamarre <ylama...@efficios.com>
---
src/bin/lttng-sessiond/lttng-sessiond.h | 2 +-
src/bin/lttng-sessiond/main.c | 2 +-
src/bin/lttng-sessiond/thread-utils.c | 39 ++++++++++++++-------------------
3 files changed, 19 insertions(+), 24 deletions(-)
diff --git a/src/bin/lttng-sessiond/lttng-sessiond.h
b/src/bin/lttng-sessiond/lttng-sessiond.h
index d321fced..6810e896 100644
--- a/src/bin/lttng-sessiond/lttng-sessiond.h
+++ b/src/bin/lttng-sessiond/lttng-sessiond.h
@@ -161,7 +161,7 @@ extern struct consumer_data kconsumer_data;
int sessiond_init_thread_quit_pipe(void);
int sessiond_check_thread_quit_pipe(int fd, uint32_t events);
-int sessiond_wait_for_quit_pipe(unsigned int timeout_us);
+int sessiond_wait_for_quit_pipe(int timeout_ms);
int sessiond_notify_quit_pipe(void);
void sessiond_close_quit_pipe(void);
diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index 57324820..a6719a4d 100644
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -1833,7 +1833,7 @@ int main(int argc, char **argv)
*/
/* Initiate teardown once activity occurs on the quit pipe. */
- sessiond_wait_for_quit_pipe(-1U);
+ sessiond_wait_for_quit_pipe(-1);
stop_threads:
/*
diff --git a/src/bin/lttng-sessiond/thread-utils.c
b/src/bin/lttng-sessiond/thread-utils.c
index 16ae9d69..e1c02290 100644
--- a/src/bin/lttng-sessiond/thread-utils.c
+++ b/src/bin/lttng-sessiond/thread-utils.c
@@ -73,41 +73,36 @@ int sessiond_check_thread_quit_pipe(int fd, uint32_t events)
* Returns 1 if the caller should quit, 0 if the timeout was reached, and
* -1 if an error was encountered.
*/
-int sessiond_wait_for_quit_pipe(unsigned int timeout_us)
+int sessiond_wait_for_quit_pipe(int timeout_ms)
{
int ret;
- fd_set read_fds;
- struct timeval timeout;
-
- FD_ZERO(&read_fds);
- FD_SET(thread_quit_pipe[0], &read_fds);
- memset(&timeout, 0, sizeof(timeout));
- timeout.tv_sec = timeout_us / USEC_PER_SEC;
- timeout.tv_usec = timeout_us % USEC_PER_SEC;
-
- while (true) {
- ret = select(thread_quit_pipe[0] + 1, &read_fds, NULL, NULL,
- timeout_us != -1U ? &timeout : NULL);
- if (ret < 0 && errno == EINTR) {
- /* Retry on interrupt. */
- continue;
- } else {
- break;
- }
- }
+ struct lttng_poll_event events;
+ ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
+ if (ret < 0) {
+ PERROR("Failure in lttng_poll_create");
+ return -1;
+ }
+ ret = lttng_poll_add(&events, thread_quit_pipe[0], LPOLLIN | LPOLLERR);
+ if (ret < 0) {
+ PERROR("Failure in lttng_poll_add");
+ ret = -1;
+ goto end;
+ }
+ ret = lttng_poll_wait(&events, timeout_ms);
if (ret > 0) {
/* Should quit. */
ret = 1;
} else if (ret < 0 && errno != EINTR) {
/* Unknown error. */
- PERROR("Failed to select() thread quit pipe");
+ PERROR("Failed to epoll()/poll() thread quit pipe");
ret = -1;
} else {
/* Timeout reached. */
ret = 0;
}
-
+end:
+ lttng_poll_clean(&events);
return ret;
}
--
2.11.0
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