From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 10 Mar 2016 00:37:56 +0000 (-0500)
Subject: Fix: application context header size
X-Git-Tag: v2.8.0-rc1~7
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=ba1c40c6095cdcb25c9c3be8bd72b09755f1f116;p=lttng-ust.git

Fix: application context header size

We need to use the RCU-dereferenced pointer when calculating the context
header size, else it may race with application context
register/unregister.

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

diff --git a/liblttng-ust/lttng-ring-buffer-client.h b/liblttng-ust/lttng-ring-buffer-client.h
index 97e1f440..1ebb14e4 100644
--- a/liblttng-ust/lttng-ring-buffer-client.h
+++ b/liblttng-ust/lttng-ring-buffer-client.h
@@ -118,7 +118,7 @@ size_t record_header_size(const struct lttng_ust_lib_ring_buffer_config *config,
 				 struct lttng_ust_lib_ring_buffer_ctx *ctx)
 {
 	struct lttng_channel *lttng_chan = channel_get_private(chan);
-	struct lttng_event *event = ctx->priv;
+	struct lttng_stack_ctx *lttng_ctx = ctx->priv2;
 	size_t orig_offset = offset;
 	size_t padding;
 
@@ -157,8 +157,8 @@ size_t record_header_size(const struct lttng_ust_lib_ring_buffer_config *config,
 		padding = 0;
 		WARN_ON_ONCE(1);
 	}
-	offset += ctx_get_size(offset, lttng_chan->ctx);
-	offset += ctx_get_size(offset, event->ctx);
+	offset += ctx_get_size(offset, lttng_ctx->chan_ctx);
+	offset += ctx_get_size(offset, lttng_ctx->event_ctx);
 
 	*pre_header_padding = padding;
 	return offset - orig_offset;