Move to kernel style SPDX license identifiers

[lttng-ust.git] / liblttng-ust / lttng-context-procname.c

diff --git a/liblttng-ust/lttng-context-procname.c b/liblttng-ust/lttng-context-procname.c
index b9bae82eba91be79fdd2ca1749fe2e5f2066b570..9622d31c61d4082f533bc4d5698936af53239903 100644 (file)
--- a/liblttng-ust/lttng-context-procname.c
+++ b/liblttng-ust/lttng-context-procname.c
@@ -1,66 +1,94 @@
 /*
- * (C) Copyright       2009-2011 -
- *             Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
- * LTTng UST procname context.
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
- * Dual LGPL v2.1/GPL v2 license.
+ * LTTng UST procname context.
  */
 
-#include <sys/prctl.h>
+#define _LGPL_SOURCE
+#include <stddef.h>
 #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_pthread_getname_np(URCU_TLS(cached_procname)[nesting], LTTNG_UST_ABI_PROCNAME_LEN);
+               URCU_TLS(cached_procname)[nesting][LTTNG_UST_ABI_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_ABI_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_ABI_PROCNAME_LEN);
 }
 
+static
+void procname_get_value(struct lttng_ctx_field *field,
+               struct lttng_ctx_value *value)
+{
+       value->u.str = wrapper_getprocname();
+}
+
+static const struct lttng_type procname_array_elem_type =
+       __type_integer(char, BYTE_ORDER, 10, UTF8);
+
 int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
 {
        struct lttng_ctx_field *field;
@@ -73,16 +101,21 @@ int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
                return -EEXIST;
        }
        field->event_field.name = "procname";
-       field->event_field.type.atype = atype_array;
-       field->event_field.type.u.array.elem_type.atype = atype_integer;
-       field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT;
-       field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT;
-       field->event_field.type.u.array.elem_type.u.basic.integer.signedness = lttng_is_signed_type(char);
-       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.atype = atype_array_nestable;
+       field->event_field.type.u.array_nestable.elem_type =
+               &procname_array_elem_type;
+       field->event_field.type.u.array_nestable.length = LTTNG_UST_ABI_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]));
+}