X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=src%2Fcommon%2Fkernel-consumer%2Fkernel-consumer.c;h=2878355a563623eefad9dc0fb56af89d86cbebc7;hb=7775df526447e504735983ee359dcb902fa6dd1e;hp=ca9755278046a2cb9174730b77fff177c274585b;hpb=bb09693bc5b9d3123e8dd5a5ac9729597b9ec3c7;p=lttng-tools.git

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index ca9755278..2878355a5 100644
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -17,6 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include <stdint.h>
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <poll.h>
@@ -123,6 +124,25 @@ int lttng_kconsumer_get_consumed_snapshot(struct lttng_consumer_stream *stream,
 	return ret;
 }
 
+static
+int get_current_subbuf_addr(struct lttng_consumer_stream *stream,
+		const char **addr)
+{
+	int ret;
+	unsigned long mmap_offset;
+	const char *mmap_base = stream->mmap_base;
+
+	ret = kernctl_get_mmap_read_offset(stream->wait_fd, &mmap_offset);
+	if (ret < 0) {
+		PERROR("Failed to get mmap read offset");
+		goto error;
+	}
+
+	*addr = mmap_base + mmap_offset;
+error:
+	return ret;
+}
+
 /*
  * Take a snapshot of all the stream of a channel
  * RCU read-side lock must be held across this function to ensure existence of
@@ -238,6 +258,7 @@ static int lttng_kconsumer_snapshot_channel(
 		while ((long) (consumed_pos - produced_pos) < 0) {
 			ssize_t read_len;
 			unsigned long len, padded_len;
+			const char *subbuf_addr;
 
 			health_code_update();
 
@@ -267,7 +288,13 @@ static int lttng_kconsumer_snapshot_channel(
 				goto error_put_subbuf;
 			}
 
-			read_len = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len,
+			ret = get_current_subbuf_addr(stream, &subbuf_addr);
+			if (ret) {
+				goto error_put_subbuf;
+			}
+
+			read_len = lttng_consumer_on_read_subbuffer_mmap(ctx,
+					stream, subbuf_addr, len,
 					padded_len - len, NULL);
 			/*
 			 * We write the padded len in local tracefiles but the data len
@@ -1684,6 +1711,9 @@ ssize_t lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 		}
 		break;
 	case CONSUMER_CHANNEL_MMAP:
+	{
+		const char *subbuf_addr;
+
 		/* Get subbuffer size without padding */
 		err = kernctl_get_subbuf_size(infd, &subbuf_size);
 		if (err != 0) {
@@ -1703,13 +1733,20 @@ ssize_t lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 			goto error;
 		}
 
+		ret = get_current_subbuf_addr(stream, &subbuf_addr);
+		if (ret) {
+			goto error_put_subbuf;
+		}
+
 		/* Make sure the tracer is not gone mad on us! */
 		assert(len >= subbuf_size);
 
 		padding = len - subbuf_size;
 
 		/* write the subbuffer to the tracefile */
-		ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, subbuf_size,
+		ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream,
+				subbuf_addr,
+				subbuf_size,
 				padding, &index);
 		/*
 		 * The mmap operation should write subbuf_size amount of data when
@@ -1729,11 +1766,12 @@ ssize_t lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 			write_index = 0;
 		}
 		break;
+	}
 	default:
 		ERR("Unknown output method");
 		ret = -EPERM;
 	}
-
+error_put_subbuf:
 	err = kernctl_put_next_subbuf(infd);
 	if (err != 0) {
 		if (err == -EFAULT) {