X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-context-procname.c;h=c6d02cf60d3b0692dd449e5f12f08a32b08307bf;hb=6e9ac4ae894690c95df4566289422c4c05ab472a;hp=caf86a95b65a509cb650e43a8c2ce10691d31dee;hpb=e92f3e285939848f248af08f11a39a04a7fcf852;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-context-procname.c b/liblttng-ust/lttng-context-procname.c
index caf86a95..c6d02cf6 100644
--- a/liblttng-ust/lttng-context-procname.c
+++ b/liblttng-ust/lttng-context-procname.c
@@ -3,7 +3,7 @@
  *
  * LTTng UST procname context.
  *
- * Copyright (C) 2009-2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -20,58 +20,83 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#include <sys/prctl.h>
+#define _LGPL_SOURCE
 #include <lttng/ust-events.h>
 #include <lttng/ust-tracer.h>
 #include <lttng/ringbuffer-config.h>
+#include <urcu/tls-compat.h>
 #include <assert.h>
+#include "compat.h"
 
-#define PROCNAME_LEN	17	/* includes \0 */
+/* Maximum number of nesting levels for the procname cache. */
+#define PROCNAME_NESTING_MAX	2
 
 /*
  * We cache the result to ensure we don't trigger a system call for
  * each event.
  * Upon exec, procname changes, but exec takes care of throwing away
  * this cached version.
+ * The procname can also change by calling prctl(). The procname should
+ * be set for a thread before the first event is logged within this
+ * thread.
  */
-static char cached_procname[17];
+typedef char procname_array[PROCNAME_NESTING_MAX][17];
+
+static DEFINE_URCU_TLS(procname_array, cached_procname);
+
+static DEFINE_URCU_TLS(int, procname_nesting);
 
 static inline
 char *wrapper_getprocname(void)
 {
-	int ret;
+	int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting));
 
-	if (caa_unlikely(!cached_procname[0])) {
-		ret = prctl(PR_GET_NAME, (unsigned long) cached_procname,
-			0, 0, 0);
-		assert(!ret);
+	if (caa_unlikely(nesting >= PROCNAME_NESTING_MAX))
+		return "<unknown>";
+	if (caa_unlikely(!URCU_TLS(cached_procname)[nesting][0])) {
+		CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting + 1);
+		/* Increment nesting before updating cache. */
+		cmm_barrier();
+		lttng_ust_getprocname(URCU_TLS(cached_procname)[nesting]);
+		URCU_TLS(cached_procname)[nesting][LTTNG_UST_PROCNAME_LEN - 1] = '\0';
+		/* Decrement nesting after updating cache. */
+		cmm_barrier();
+		CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting);
 	}
-	return cached_procname;
+	return URCU_TLS(cached_procname)[nesting];
 }
 
+/* Reset should not be called from a signal handler. */
 void lttng_context_procname_reset(void)
 {
-	cached_procname[0] = '\0';
+	CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0');
+	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1);
+	CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0');
+	CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0);
 }
 
 static
-size_t procname_get_size(size_t offset)
+size_t procname_get_size(struct lttng_ctx_field *field, size_t offset)
 {
-	size_t size = 0;
-
-	size += PROCNAME_LEN;
-	return size;
+	return LTTNG_UST_PROCNAME_LEN;
 }
 
 static
 void procname_record(struct lttng_ctx_field *field,
 		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
-		 struct ltt_channel *chan)
+		 struct lttng_channel *chan)
 {
 	char *procname;
 
 	procname = wrapper_getprocname();
-	chan->ops->event_write(ctx, procname, PROCNAME_LEN);
+	chan->ops->event_write(ctx, procname, LTTNG_UST_PROCNAME_LEN);
+}
+
+static
+void procname_get_value(struct lttng_ctx_field *field,
+		struct lttng_ctx_value *value)
+{
+	value->u.str = wrapper_getprocname();
 }
 
 int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
@@ -94,8 +119,18 @@ int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
 	field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0;
 	field->event_field.type.u.array.elem_type.u.basic.integer.base = 10;
 	field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8;
-	field->event_field.type.u.array.length = PROCNAME_LEN;
+	field->event_field.type.u.array.length = LTTNG_UST_PROCNAME_LEN;
 	field->get_size = procname_get_size;
 	field->record = procname_record;
+	field->get_value = procname_get_value;
+	lttng_context_update(*ctx);
 	return 0;
 }
+
+/*
+ * Force a read (imply TLS fixup for dlopen) of TLS variables.
+ */
+void lttng_fixup_procname_tls(void)
+{
+	asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0]));
+}