From 51920067af7b1049413c1b8c30ee254afbd4e448 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 9 Feb 2012 18:55:44 -0500 Subject: [PATCH] Fix tracepoint.h multiple .o within module/core exec linkage bug We need all symbols looked up with dlopen to share the same linkage property as the __tracepoint_registered variable (shared across .o in a module/executable), otherwise only the first .o which runs its constructor will have those defined. Caused some tracepoints not to be traced in non-_LGPL_SOURCE applications, due to the check: if (!TP_RCU_LINK_TEST()) \ return; Signed-off-by: Mathieu Desnoyers --- include/lttng/tracepoint-rcu.h | 14 ++++---- include/lttng/tracepoint.h | 66 +++++++++++++++++++++------------- 2 files changed, 48 insertions(+), 32 deletions(-) diff --git a/include/lttng/tracepoint-rcu.h b/include/lttng/tracepoint-rcu.h index 852cfe48..23dab7d6 100644 --- a/include/lttng/tracepoint-rcu.h +++ b/include/lttng/tracepoint-rcu.h @@ -23,27 +23,25 @@ #include -#define TP_RCU_LINK_TEST() 1 #define tp_rcu_read_lock_bp rcu_read_lock_bp #define tp_rcu_read_unlock_bp rcu_read_unlock_bp #define tp_rcu_dereference_bp rcu_dereference_bp +#define TP_RCU_LINK_TEST() 1 #else /* _LGPL_SOURCE */ -#define TP_RCU_LINK_TEST() tp_rcu_read_lock_bp - -/* Symbols looked up with dlsym */ -static void (*tp_rcu_read_lock_bp)(void) __attribute__((unused)); -static void (*tp_rcu_read_unlock_bp)(void) __attribute__((unused)); -static void *(*tp_rcu_dereference_sym_bp)(void *p) __attribute__((unused)); +#define tp_rcu_read_lock_bp tracepoint_dlopen.rcu_read_lock_sym_bp +#define tp_rcu_read_unlock_bp tracepoint_dlopen.rcu_read_unlock_sym_bp #define tp_rcu_dereference_bp(p) \ ({ \ typeof(p) _________p1 = URCU_FORCE_CAST(typeof(p), \ - tp_rcu_dereference_sym_bp(URCU_FORCE_CAST(void *, p))); \ + tracepoint_dlopen.rcu_dereference_sym_bp(URCU_FORCE_CAST(void *, p))); \ (_________p1); \ }) +#define TP_RCU_LINK_TEST() tp_rcu_read_lock_bp + #endif /* _LGPL_SOURCE */ #endif /* _LTTNG_TRACEPOINT_RCU_H */ diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h index fe18c5b7..e4941b5a 100644 --- a/include/lttng/tracepoint.h +++ b/include/lttng/tracepoint.h @@ -18,6 +18,7 @@ #include #include #include /* for dlopen */ +#include /* for memset */ #include #ifdef __cplusplus @@ -150,6 +151,25 @@ static inline void __tracepoint_unregister_##_provider##___##_name(char *name, extern int __tracepoint_probe_register(const char *name, void *func, void *data); extern int __tracepoint_probe_unregister(const char *name, void *func, void *data); +/* + * tracepoint dynamic linkage handling (callbacks). Hidden visibility: + * shared across objects in a module/main executable. + */ +struct tracepoint_dlopen { + void *liblttngust_handle; + + int (*tracepoint_register_lib)(struct tracepoint * const *tracepoints_start, + int tracepoints_count); + int (*tracepoint_unregister_lib)(struct tracepoint * const *tracepoints_start); +#ifndef _LGPL_SOURCE + void (*rcu_read_lock_sym_bp)(void); + void (*rcu_read_unlock_sym_bp)(void); + void *(*rcu_dereference_sym_bp)(void *p); +#endif +}; + +extern struct tracepoint_dlopen tracepoint_dlopen; + #ifdef TRACEPOINT_DEFINE /* @@ -185,11 +205,6 @@ extern int __tracepoint_probe_unregister(const char *name, void *func, void *dat __attribute__((used, section("__tracepoints_ptrs"))) = \ &__tracepoint_##provider##___##name; -static int (*tracepoint_register_lib)(struct tracepoint * const *tracepoints_start, - int tracepoints_count); -static int (*tracepoint_unregister_lib)(struct tracepoint * const *tracepoints_start); -static void *liblttngust_handle; - /* * These weak symbols, the constructor, and destructor take care of * registering only _one_ instance of the tracepoints per shared-ojbect @@ -201,38 +216,41 @@ extern struct tracepoint * const __stop___tracepoints_ptrs[] __attribute__((weak, visibility("hidden"))); int __tracepoint_registered __attribute__((weak, visibility("hidden"))); +struct tracepoint_dlopen tracepoint_dlopen + __attribute__((weak, visibility("hidden"))); static void __attribute__((constructor)) __tracepoints__init(void) { if (__tracepoint_registered++) return; - liblttngust_handle = dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL); - if (!liblttngust_handle) + tracepoint_dlopen.liblttngust_handle = + dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL); + if (!tracepoint_dlopen.liblttngust_handle) return; - tracepoint_register_lib = + tracepoint_dlopen.tracepoint_register_lib = URCU_FORCE_CAST(int (*)(struct tracepoint * const *, int), - dlsym(liblttngust_handle, + dlsym(tracepoint_dlopen.liblttngust_handle, "tracepoint_register_lib")); - tracepoint_unregister_lib = + tracepoint_dlopen.tracepoint_unregister_lib = URCU_FORCE_CAST(int (*)(struct tracepoint * const *), - dlsym(liblttngust_handle, + dlsym(tracepoint_dlopen.liblttngust_handle, "tracepoint_unregister_lib")); #ifndef _LGPL_SOURCE - tp_rcu_read_lock_bp = + tracepoint_dlopen.rcu_read_lock_sym_bp = URCU_FORCE_CAST(void (*)(void), - dlsym(liblttngust_handle, + dlsym(tracepoint_dlopen.liblttngust_handle, "tp_rcu_read_lock_bp")); - tp_rcu_read_unlock_bp = + tracepoint_dlopen.rcu_read_unlock_sym_bp = URCU_FORCE_CAST(void (*)(void), - dlsym(liblttngust_handle, + dlsym(tracepoint_dlopen.liblttngust_handle, "tp_rcu_read_unlock_bp")); - tp_rcu_dereference_sym_bp = + tracepoint_dlopen.rcu_dereference_sym_bp = URCU_FORCE_CAST(void *(*)(void *p), - dlsym(liblttngust_handle, + dlsym(tracepoint_dlopen.liblttngust_handle, "tp_rcu_dereference_sym_bp")); #endif - tracepoint_register_lib(__start___tracepoints_ptrs, + tracepoint_dlopen.tracepoint_register_lib(__start___tracepoints_ptrs, __stop___tracepoints_ptrs - __start___tracepoints_ptrs); } @@ -240,15 +258,15 @@ static void __attribute__((constructor)) __tracepoints__init(void) static void __attribute__((destructor)) __tracepoints__destroy(void) { int ret; + if (--__tracepoint_registered) return; - if (tracepoint_unregister_lib) - tracepoint_unregister_lib(__start___tracepoints_ptrs); - if (liblttngust_handle) { - tracepoint_unregister_lib = NULL; - tracepoint_register_lib = NULL; - ret = dlclose(liblttngust_handle); + if (tracepoint_dlopen.tracepoint_unregister_lib) + tracepoint_dlopen.tracepoint_unregister_lib(__start___tracepoints_ptrs); + if (tracepoint_dlopen.liblttngust_handle) { + ret = dlclose(tracepoint_dlopen.liblttngust_handle); assert(!ret); + memset(&tracepoint_dlopen, 0, sizeof(tracepoint_dlopen)); } } -- 2.34.1