Change in libosmocore[master]: select: Make file descriptor lists per-thread

Harald Welte gerrit-no-reply at
Sat Apr 6 16:18:38 UTC 2019

Harald Welte has uploaded this change for review. (

Change subject: select: Make file descriptor lists per-thread

select: Make file descriptor lists per-thread

In a multi-threaded environemnt, it's likely that each thread will have
its own, distinct set of file descriptors that it wants to watch.

Hence, let's make the osmo_fd_* functions configure not one global
list of file descriptors, but a thread-local list of file descriptors.

Change-Id: I5082ed3e500ad1a7516e1785bc57e008da2fac9a
M include/osmocom/core/select.h
M src/select.c
2 files changed, 18 insertions(+), 3 deletions(-)

  git pull ssh:// refs/changes/37/13537/1

diff --git a/include/osmocom/core/select.h b/include/osmocom/core/select.h
index a200b6f..92904e2 100644
--- a/include/osmocom/core/select.h
+++ b/include/osmocom/core/select.h
@@ -52,6 +52,7 @@
 void osmo_fd_close(struct osmo_fd *fd);
 int osmo_select_main(int polling);
 int osmo_select_main_ctx(int polling);
+void osmo_select_init(void);
 struct osmo_fd *osmo_fd_get_by_fd(int fd);
diff --git a/src/select.c b/src/select.c
index d7679e9..f96a548 100644
--- a/src/select.c
+++ b/src/select.c
@@ -50,9 +50,11 @@
  * \file select.c */
-static int maxfd = 0;
-static LLIST_HEAD(osmo_fds);
-static int unregistered_count;
+/* keep a set of file descriptors per-thread, so that each thread can have its own
+ * distinct set of file descriptors to interact with */
+static __thread int maxfd = 0;
+static __thread struct llist_head osmo_fds; /* TLS cannot use LLIST_HEAD() */
+static __thread int unregistered_count;
 /*! Set up an osmo-fd. Will not register it.
  *  \param[inout] ofd Osmo FD to be set-up
@@ -308,6 +310,18 @@
 	return NULL;
+/*! initialize the osmocom select abstraction for the current thread */
+void osmo_select_init(void)
+	INIT_LLIST_HEAD(&osmo_fds);
+/* ensure main thread always has pre-initialized osmo_fds */
+static __attribute__((constructor)) void on_dso_load_select(void)
+	osmo_select_init();
 #include <sys/timerfd.h>

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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I5082ed3e500ad1a7516e1785bc57e008da2fac9a
Gerrit-Change-Number: 13537
Gerrit-PatchSet: 1
Gerrit-Owner: Harald Welte <laforge at>
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