From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Fri, 1 Nov 2013 13:42:23 +0000 (-0400)
Subject: Fix: tls-compat multi-lib conflict
X-Git-Tag: v0.9.0~131
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=ae62f05acabbf4cbb2877331befd57ee168a5587;p=userspace-rcu.git

Fix: tls-compat multi-lib conflict

When configured with the TLS pthread key fallback either:

- explicitly with ./configure --disable-compiler-tls,
- or if compiler TLS is not usable,

(this can be confirmed by looking at the configure output:
Thread Local Storage (TLS): pthread_getspecific().)

There is an issue when using multiple flavors of RCU within the same
program. Unit tests concerned:

tests/unit/test_urcu_multiflavor
tests/unit/test_urcu_multiflavor_dynlink

Vladimir Nikulichev noticed crashes when using this setup. The problem
can be pinpointed to a missing macro expansion in urcu/tls-compat.h:

looking at the output of

nm tests/unit/.libs/test_urcu_multiflavor :

                 U __tls_access_rcu_reader

this seems to be the issue. We're missing macro expansion in
tls-compat.h. With this commit, it becomes:

                 U __tls_access_rcu_reader_bp
                 U __tls_access_rcu_reader_mb
                 U __tls_access_rcu_reader_memb
                 U __tls_access_rcu_reader_sig

Please note that this affects an unusual configuration of userspace RCU
(with TLS pthread key fallback), needed for some BSD that don't support
compiler TLS. Strictly speaking, this requires bumping the URCU library
soname version major number, because it breaks the ABI presented to
applications on those unusual configurations.

A following commit will handle the ABI migration: for stable releases
(stable-0.7 and stable-0.8 branches), the ABI is kept compatible, and
bogus usage are detected. For the upcoming stable-0.9, the soname will
simply be bumped.

Reported-by: Vladimir Nikulichev <nvs@tbricks.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/urcu/tls-compat.h b/urcu/tls-compat.h
index a44b88d..8ac1ea0 100644
--- a/urcu/tls-compat.h
+++ b/urcu/tls-compat.h
@@ -74,6 +74,10 @@ extern "C" {
 
 #else /* #ifndef CONFIG_RCU_TLS */
 
+/*
+ * The *_1() macros ensure macro parameters are expanded.
+ */
+
 # include <pthread.h>
 
 struct urcu_tls {
@@ -82,14 +86,16 @@ struct urcu_tls {
 	int init_done;
 };
 
-# define DECLARE_URCU_TLS(type, name)				\
+# define DECLARE_URCU_TLS_1(type, name)				\
 	type *__tls_access_ ## name(void)
+# define DECLARE_URCU_TLS(type, name)				\
+	DECLARE_URCU_TLS_1(type, name)
 
 /*
  * Note: we don't free memory at process exit, since it will be dealt
  * with by the OS.
  */
-# define DEFINE_URCU_TLS(type, name)				\
+# define DEFINE_URCU_TLS_1(type, name)				\
 	type *__tls_access_ ## name(void)			\
 	{							\
 		static struct urcu_tls __tls_ ## name = {	\
@@ -118,7 +124,12 @@ struct urcu_tls {
 		return __tls_p;					\
 	}
 
-# define URCU_TLS(name)		(*__tls_access_ ## name())
+# define DEFINE_URCU_TLS(type, name)				\
+	DEFINE_URCU_TLS_1(type, name)
+
+# define URCU_TLS_1(name)	(*__tls_access_ ## name())
+
+# define URCU_TLS(name)		URCU_TLS_1(name)
 
 #endif	/* #else #ifndef CONFIG_RCU_TLS */