From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Sat, 1 Oct 2016 22:59:17 +0000 (-0400)
Subject: Fix: perform TLS fixup in all UST entry points from each thread
X-Git-Tag: v2.8.2~6
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=a3b964ebc0510bacc9af2d729f1a68c2e3ccc95d

Fix: perform TLS fixup in all UST entry points from each thread

Each entry point into lttng-ust that end up taking the ust lock need to
perform a TLS fixup for each thread. Add a TLS fixup in both listener
threads, in fork and base address dump helper libs, and in app context
and tracepoint probe registration/unregistration functions, which can be
called from application threads.

Those ensure we don't take the libc dl lock within the ust lock when
performing the TLS lazy fixup.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/liblttng-ust/lttng-context-provider.c b/liblttng-ust/lttng-context-provider.c
index 6c067e2f..e6749bee 100644
--- a/liblttng-ust/lttng-context-provider.c
+++ b/liblttng-ust/lttng-context-provider.c
@@ -67,6 +67,8 @@ int lttng_ust_context_provider_register(struct lttng_ust_context_provider *provi
 	uint32_t hash;
 	int ret = 0;
 
+	lttng_ust_fixup_tls();
+
 	/* Provider name starts with "$app.". */
 	if (strncmp("$app.", provider->name, strlen("$app.") != 0))
 		return -EINVAL;
@@ -94,6 +96,8 @@ end:
 
 void lttng_ust_context_provider_unregister(struct lttng_ust_context_provider *provider)
 {
+	lttng_ust_fixup_tls();
+
 	if (ust_lock())
 		goto end;
 	lttng_ust_context_set_session_provider(provider->name,
diff --git a/liblttng-ust/lttng-probes.c b/liblttng-ust/lttng-probes.c
index bba5cd34..4b525923 100644
--- a/liblttng-ust/lttng-probes.c
+++ b/liblttng-ust/lttng-probes.c
@@ -194,6 +194,8 @@ int lttng_probe_register(struct lttng_probe_desc *desc)
 {
 	int ret = 0;
 
+	lttng_ust_fixup_tls();
+
 	/*
 	 * If version mismatch, don't register, but don't trigger assert
 	 * on caller. The version check just prints an error.
@@ -234,6 +236,8 @@ int ltt_probe_register(struct lttng_probe_desc *desc)
 
 void lttng_probe_unregister(struct lttng_probe_desc *desc)
 {
+	lttng_ust_fixup_tls();
+
 	if (!check_provider_version(desc))
 		return;
 
diff --git a/liblttng-ust/lttng-tracer-core.h b/liblttng-ust/lttng-tracer-core.h
index 44aca749..ba232f32 100644
--- a/liblttng-ust/lttng-tracer-core.h
+++ b/liblttng-ust/lttng-tracer-core.h
@@ -62,5 +62,6 @@ void lttng_ust_dummy_record(struct lttng_ctx_field *field,
 void lttng_ust_dummy_get_value(struct lttng_ctx_field *field,
 		struct lttng_ctx_value *value);
 int lttng_context_is_app(const char *name);
+void lttng_ust_fixup_tls(void);
 
 #endif /* _LTTNG_TRACER_CORE_H */
diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 6c6eeda5..07c1be09 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -388,6 +388,16 @@ void lttng_fixup_urcu_bp_tls(void)
 	rcu_read_unlock();
 }
 
+void lttng_ust_fixup_tls(void)
+{
+	lttng_fixup_urcu_bp_tls();
+	lttng_fixup_ringbuffer_tls();
+	lttng_fixup_vtid_tls();
+	lttng_fixup_nest_count_tls();
+	lttng_fixup_procname_tls();
+	lttng_fixup_ust_mutex_nest_tls();
+}
+
 int lttng_get_notify_socket(void *owner)
 {
 	struct sock_info *info = owner;
@@ -1295,6 +1305,8 @@ void *ust_listener_thread(void *arg)
 	int sock, ret, prev_connect_failed = 0, has_waited = 0;
 	long timeout;
 
+	lttng_ust_fixup_tls();
+
 	/* Restart trying to connect to the session daemon */
 restart:
 	if (prev_connect_failed) {
@@ -1558,12 +1570,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
 	 * to be the dynamic linker mutex) and ust_lock, taken within
 	 * the ust lock.
 	 */
-	lttng_fixup_urcu_bp_tls();
-	lttng_fixup_ringbuffer_tls();
-	lttng_fixup_vtid_tls();
-	lttng_fixup_nest_count_tls();
-	lttng_fixup_procname_tls();
-	lttng_fixup_ust_mutex_nest_tls();
+	lttng_ust_fixup_tls();
 
 	/*
 	 * We want precise control over the order in which we construct
@@ -1792,6 +1799,9 @@ void ust_before_fork(sigset_t *save_sigset)
 	sigset_t all_sigs;
 	int ret;
 
+	/* Fixup lttng-ust TLS. */
+	lttng_ust_fixup_tls();
+
 	if (URCU_TLS(lttng_ust_nest_count))
 		return;
 	/* Disable signals */
diff --git a/liblttng-ust/lttng-ust-statedump.c b/liblttng-ust/lttng-ust-statedump.c
index 4242579f..e1fbe053 100644
--- a/liblttng-ust/lttng-ust-statedump.c
+++ b/liblttng-ust/lttng-ust-statedump.c
@@ -315,6 +315,12 @@ int do_baddr_statedump(void *owner)
 	if (getenv("LTTNG_UST_WITHOUT_BADDR_STATEDUMP"))
 		return 0;
 
+	/*
+	 * Fixup lttng-ust TLS when called from dlopen/dlclose
+	 * instrumentation.
+	 */
+	lttng_ust_fixup_tls();
+
 	data.owner = owner;
 	data.exec_found = 0;
 	/*