From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 1 Mar 2012 17:09:40 +0000 (-0500)
Subject: Fix: fixup ringbuffer tls at constructor by forcing read
X-Git-Tag: v2.0.0-rc2~13
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=f645cfa794fc481dff6cb30ea56e93f825b3d423;p=lttng-ust.git

Fix: fixup ringbuffer tls at constructor by forcing read

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

Conflicts:

	liblttng-ust/lttng-ust-comm.c
	libringbuffer/ring_buffer_frontend.c
---

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index fa184ad7..b90df861 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -46,6 +46,7 @@
 #include <usterr-signal-safe.h>
 #include "tracepoint-internal.h"
 #include "ltt-tracer-core.h"
+#include "../libringbuffer/tlsfixup.h"
 
 /*
  * Has lttng ust comm constructor been called ?
@@ -838,6 +839,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
 	 * the ust lock.
 	 */
 	lttng_fixup_event_tls();
+	lttng_fixup_ringbuffer_tls();
 
 	/*
 	 * We want precise control over the order in which we construct
diff --git a/libringbuffer/Makefile.am b/libringbuffer/Makefile.am
index 9bd85868..b5b0ebd1 100644
--- a/libringbuffer/Makefile.am
+++ b/libringbuffer/Makefile.am
@@ -11,7 +11,7 @@ libringbuffer_la_SOURCES = \
 	api.h \
 	backend.h backend_internal.h backend_types.h \
 	frontend_api.h frontend.h frontend_internal.h frontend_types.h \
-	nohz.h vatomic.h
+	nohz.h vatomic.h tlsfixup.h
 	
 libringbuffer_la_LIBADD = \
 	-lpthread \
diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index 0996ecef..970fde90 100644
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -53,6 +53,7 @@
 #include "backend.h"
 #include "frontend.h"
 #include "shm.h"
+#include "tlsfixup.h"
 
 #ifndef max
 #define max(a, b)	((a) > (b) ? (a) : (b))
@@ -1507,3 +1508,11 @@ int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx)
 	ctx->buf_offset = offsets.begin + offsets.pre_header_padding;
 	return 0;
 }
+
+/*
+ * Force a read (imply TLS fixup for dlopen) of TLS variables.
+ */
+void lttng_fixup_ringbuffer_tls(void)
+{
+	asm volatile ("" : : "m" (lib_ring_buffer_nesting));
+}
diff --git a/libringbuffer/tlsfixup.h b/libringbuffer/tlsfixup.h
new file mode 100644
index 00000000..84ba889e
--- /dev/null
+++ b/libringbuffer/tlsfixup.h
@@ -0,0 +1,14 @@
+#ifndef _LTTNG_UST_LIB_RINGBUFFER_TLS_FIXUP_H
+#define _LTTNG_UST_LIB_RINGBUFFER_TLS_FIXUP_H
+
+/*
+ * libringbuffer/tlsfixup.h
+ *
+ * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+void lttng_fixup_ringbuffer_tls(void);
+
+#endif /* _LTTNG_UST_LIB_RINGBUFFER_TLS_FIXUP_H */