/*
- * (C) Copyright 2009-2011 -
- * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * lttng-context-procname.c
*
* LTTng UST procname context.
*
- * Dual LGPL v2.1/GPL v2 license.
+ * 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
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
+#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"
+/* 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)
{
- if (caa_unlikely(!cached_procname[0])) {
- lttng_ust_getprocname(cached_procname);
- cached_procname[LTTNG_UST_PROCNAME_LEN - 1] = '\0';
+ int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting));
+
+ 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;
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;
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)
+{
+ char *procname;
+
+ procname = wrapper_getprocname();
+ value->u.str = procname;
+}
+
int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
{
struct lttng_ctx_field *field;
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]));
+}