X-Git-Url: http://git.liburcu.org/?p=lttng-modules.git;a=blobdiff_plain;f=lttng-context-callstack.c;h=0876b12269ecc26a90c73b948d8c0dc9bb954f6e;hp=fd730bbc164090bdaf9ef708a4265894de2154a7;hb=80bb26003945e96a8ade9c8788dab9b2e08cbc08;hpb=3685cc8094c0fdf561f1ef6379f0e451d14d149e

diff --git a/lttng-context-callstack.c b/lttng-context-callstack.c
index fd730bbc..0876b122 100644
--- a/lttng-context-callstack.c
+++ b/lttng-context-callstack.c
@@ -1,4 +1,5 @@
-/*
+/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
+ *
  * lttng-context-callstack.c
  *
  * LTTng callstack event context.
@@ -6,20 +7,6 @@
  * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.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
- *
  * The callstack context can be added to any kernel event. It records
  * either the kernel or the userspace callstack, up to a max depth. The
  * context is a CTF sequence, such that it uses only the space required
@@ -120,14 +107,26 @@ int init_type(enum lttng_cs_ctx_modes mode)
 	return 0;
 }
 
+/* Keep track of nesting inside userspace callstack context code */
+DEFINE_PER_CPU(int, callstack_user_nesting);
+
 static
 struct stack_trace *stack_trace_context(struct lttng_ctx_field *field,
 					struct lib_ring_buffer_ctx *ctx)
 {
-	int nesting;
+	int buffer_nesting, cs_user_nesting;
 	struct lttng_cs *cs;
 	struct field_data *fdata = field->priv;
 
+	/*
+	 * Do not gather the userspace callstack context when the event was
+	 * triggered by the userspace callstack context saving mechanism.
+	 */
+	cs_user_nesting = per_cpu(callstack_user_nesting, ctx->cpu);
+
+	if (fdata->mode == CALLSTACK_USER && cs_user_nesting >= 1)
+		return NULL;
+
 	/*
 	 * get_cpu() is not required, preemption is already
 	 * disabled while event is written.
@@ -136,11 +135,11 @@ struct stack_trace *stack_trace_context(struct lttng_ctx_field *field,
 	 * Check it again as a safety net.
 	 */
 	cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
-	nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
-	if (nesting >= RING_BUFFER_MAX_NESTING) {
+	buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
+	if (buffer_nesting >= RING_BUFFER_MAX_NESTING)
 		return NULL;
-	}
-	return &cs->dispatch[nesting].stack_trace;
+
+	return &cs->dispatch[buffer_nesting].stack_trace;
 }
 
 /*
@@ -168,8 +167,15 @@ size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field,
 	/* reset stack trace, no need to clear memory */
 	trace->nr_entries = 0;
 
+	if (fdata->mode == CALLSTACK_USER)
+		++per_cpu(callstack_user_nesting, ctx->cpu);
+
 	/* do the real work and reserve space */
 	cs_types[fdata->mode].save_func(trace);
+
+	if (fdata->mode == CALLSTACK_USER)
+		per_cpu(callstack_user_nesting, ctx->cpu)--;
+
 	/*
 	 * Remove final ULONG_MAX delimiter. If we cannot find it, add
 	 * our own marker to show that the stack is incomplete. This is
@@ -348,14 +354,12 @@ int lttng_add_callstack_to_ctx(struct lttng_ctx **ctx, int type)
 	switch (type) {
 	case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL:
 		return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL);
+#ifdef CONFIG_X86
 	case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER:
 		return __lttng_add_callstack_generic(ctx, CALLSTACK_USER);
+#endif
 	default:
 		return -EINVAL;
 	}
 }
 EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx);
-
-MODULE_LICENSE("GPL and additional rights");
-MODULE_AUTHOR("Francis Giraldeau");
-MODULE_DESCRIPTION("Linux Trace Toolkit Callstack Support");