From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 13 Nov 2014 19:58:22 +0000 (-0500)
Subject: Print error rather than abort
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=8a325ad789d5a2c5e079dd210c2c6c40a1703195;p=userspace-rcu.git

Print error rather than abort

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

diff --git a/Makefile.am b/Makefile.am
index 7ead5f0..8fbf11d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -59,6 +59,7 @@ lib_LTLIBRARIES = liburcu-common.la \
 #
 liburcu_common_la_SOURCES = wfqueue.c wfcqueue.c wfstack.c $(COMPAT) \
 		urcu-checker.c
+liburcu_common_la_LDFLAGS = -ldl
 
 liburcu_la_SOURCES = urcu.c urcu-pointer.c $(COMPAT)
 liburcu_la_LIBADD = liburcu-common.la
diff --git a/tests/benchmark/Makefile.am b/tests/benchmark/Makefile.am
index b8cf35d..17c1fe0 100644
--- a/tests/benchmark/Makefile.am
+++ b/tests/benchmark/Makefile.am
@@ -1,7 +1,7 @@
 if !LIBC_INCLUDES_PTHREAD
 AM_LDFLAGS=-lpthread
 endif
-AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir) -I$(top_srcdir)/tests/common -g
+AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir) -I$(top_srcdir)/tests/common -g -ldl
 
 noinst_PROGRAMS = test_urcu test_urcu_dynamic_link test_urcu_timing \
 	test_urcu_signal test_urcu_signal_dynamic_link test_urcu_signal_timing \
diff --git a/tests/regression/Makefile.am b/tests/regression/Makefile.am
index 354ad1a..8701e9b 100644
--- a/tests/regression/Makefile.am
+++ b/tests/regression/Makefile.am
@@ -1,7 +1,7 @@
 if !LIBC_INCLUDES_PTHREAD
 AM_LDFLAGS=-lpthread
 endif
-AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir) -I$(top_srcdir)/tests/common -g
+AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir) -I$(top_srcdir)/tests/common -g -ldl
 
 noinst_PROGRAMS = test_urcu_fork \
 	rcutorture_urcu \
diff --git a/tests/unit/Makefile.am b/tests/unit/Makefile.am
index cd40b39..97275a6 100644
--- a/tests/unit/Makefile.am
+++ b/tests/unit/Makefile.am
@@ -1,7 +1,7 @@
 if !LIBC_INCLUDES_PTHREAD
 AM_LDFLAGS=-lpthread
 endif
-AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir) -I$(top_srcdir)/tests/common -g
+AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir) -I$(top_srcdir)/tests/common -g -ldl
 
 noinst_PROGRAMS = test_uatomic \
 	test_urcu_multiflavor \
diff --git a/urcu-checker.c b/urcu-checker.c
index 234bd9b..cd4721d 100644
--- a/urcu-checker.c
+++ b/urcu-checker.c
@@ -20,14 +20,51 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/*
+ * NOTE: build application with -rdynamic -ldl -lurcu-common.
+ */
+
+#define _GNU_SOURCE
 #include <string.h>
 #include <assert.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <execinfo.h>
+#include <dlfcn.h>
+#include <sys/types.h>
 #include <urcu/urcu-checker.h>
 #include <urcu/tls-compat.h>
 
-#define URCU_DEBUG_STACK_LEN	10
+#define URCU_DEBUG_STACK_LEN		10
+#define DEFAULT_PRINT_BACKTRACE_LEN	5
+#define BACKTRACE_LEN			16
+
+#ifdef __linux__
+#include <syscall.h>
+#endif
+
+#if defined(_syscall0)
+_syscall0(pid_t, gettid)
+#elif defined(__NR_gettid)
+#include <unistd.h>
+static inline pid_t gettid(void)
+{
+	return syscall(__NR_gettid);
+}
+#else
+#include <sys/types.h>
+#include <unistd.h>
+
+/* Fall-back on getpid for tid if not available. */
+static inline pid_t gettid(void)
+{
+	return getpid();
+}
+#endif
+
+#define err_printf(fmt, args...) \
+	fprintf(stderr, "[urcu-checker %ld/%ld] "  fmt, \
+		(long) getpid(), (long) gettid(), ## args)
 
 struct urcu_debug_entry {
 	void *ip;
@@ -39,8 +76,72 @@ struct urcu_debug_stack {
 	int stackend;
 };
 
+struct backtrace {
+	void *ptrs[BACKTRACE_LEN];
+	char **symbols;
+};
+
 static DEFINE_URCU_TLS(struct urcu_debug_stack, rcu_debug_stack);
 
+static volatile int print_backtrace_len = DEFAULT_PRINT_BACKTRACE_LEN;
+
+/*
+ * Allocates a string, or NULL.
+ */
+static
+char *get_symbol(const void *caller)
+{
+	Dl_info info;
+	char *caller_symbol;
+
+	if (caller && dladdr(caller, &info) && info.dli_sname) {
+		caller_symbol = strdup(info.dli_sname);
+	} else {
+		caller_symbol = NULL;
+	}
+	return caller_symbol;
+}
+
+static inline __attribute__((always_inline))
+void save_backtrace(struct backtrace *bt)
+{
+	memset(bt, 0, sizeof(*bt));
+	(void) backtrace(bt->ptrs, BACKTRACE_LEN);
+	bt->symbols = backtrace_symbols(bt->ptrs, BACKTRACE_LEN);
+}
+
+static
+void free_backtrace(struct backtrace *bt)
+{
+	free(bt->symbols);
+}
+
+static
+void print_bt(struct backtrace *bt)
+{
+	int j;
+	unsigned int empty = 1;
+
+	for (j = 0; j < BACKTRACE_LEN; j++) {
+		if (bt->ptrs[j]) {
+			empty = 0;
+			break;
+		}
+	}
+	if (empty)
+		return;
+
+	err_printf("[backtrace]\n");
+	for (j = 0; j < BACKTRACE_LEN && j < print_backtrace_len; j++) {
+		if (!bt->ptrs[j])
+			continue;
+		if (bt->symbols)
+			err_printf(" %p <%s>\n", bt->ptrs[j], bt->symbols[j]);
+		else
+			err_printf(" %p\n", bt->ptrs[j]);
+	}
+}
+
 void rcu_read_lock_debug(void)
 {
 	struct urcu_debug_stack *r = &URCU_TLS(rcu_debug_stack);
@@ -61,8 +162,13 @@ void rcu_read_ongoing_check_debug(const char *func)
 	struct urcu_debug_stack *r = &URCU_TLS(rcu_debug_stack);
 
 	if (r->stackend == 0) {
-		fprintf(stderr, "URCU LOCKED CHECK failure: %p\n",
-			__builtin_return_address(0));
-		abort();
+		struct backtrace bt;
+
+		err_printf("rcu_dereference() used outside of critical section at %p <%s>\n",
+			__builtin_return_address(0),
+			get_symbol(__builtin_return_address(0)));
+		save_backtrace(&bt);
+		print_bt(&bt);
+		free_backtrace(&bt);
 	}
 }