Fix: create/destroy a splice_pipe per stream

We had a per-thread splice_pipe (one for data and one for metadata), but
in case of error, we would end up filling the write side of the pipe and
never emptying it. This could lead to leaking data from one session to
the other, but also to stall the consumer trying to splice into a full
pipe.

Now we create a splice_pipe per-stream, so it is destroyed when the
session is destroyed.

Fixes: #726
Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/consumer-stream.c b/src/common/consumer-stream.c
index 8fe02e74eaa8dfe59b90ed4fbe2d6b4cf13b637b..92576aab408a193530e56f1d3739c47f43d58b35 100644 (file)
--- a/src/common/consumer-stream.c
+++ b/src/common/consumer-stream.c
@@ -28,6 +28,7 @@
 #include <common/kernel-consumer/kernel-consumer.h>
 #include <common/relayd/relayd.h>
 #include <common/ust-consumer/ust-consumer.h>
+#include <common/utils.h>
 
 #include "consumer-stream.h"
 
@@ -119,6 +120,9 @@ void consumer_stream_close(struct lttng_consumer_stream *stream)
                        }
                        stream->wait_fd = -1;
                }
+               if (stream->chan->output == CONSUMER_CHANNEL_SPLICE) {
+                       utils_close_pipe(stream->splice_pipe);
+               }
                break;
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:

diff --git a/src/common/consumer.c b/src/common/consumer.c
index 999e400059fbe763264698a75c67b3fb80d6c717..755aa5ee888a052dec4b11da43d355fa437456b2 100644 (file)
--- a/src/common/consumer.c
+++ b/src/common/consumer.c
@@ -1302,12 +1302,6 @@ struct lttng_consumer_local_data *lttng_consumer_create(
                goto error_quit_pipe;
        }
 
-       ret = pipe(ctx->consumer_thread_pipe);
-       if (ret < 0) {
-               PERROR("Error creating thread pipe");
-               goto error_thread_pipe;
-       }
-
        ret = pipe(ctx->consumer_channel_pipe);
        if (ret < 0) {
                PERROR("Error creating channel pipe");
@@ -1319,20 +1313,11 @@ struct lttng_consumer_local_data *lttng_consumer_create(
                goto error_metadata_pipe;
        }
 
-       ret = utils_create_pipe(ctx->consumer_splice_metadata_pipe);
-       if (ret < 0) {
-               goto error_splice_pipe;
-       }
-
        return ctx;
 
-error_splice_pipe:
-       lttng_pipe_destroy(ctx->consumer_metadata_pipe);
 error_metadata_pipe:
        utils_close_pipe(ctx->consumer_channel_pipe);
 error_channel_pipe:
-       utils_close_pipe(ctx->consumer_thread_pipe);
-error_thread_pipe:
        utils_close_pipe(ctx->consumer_should_quit);
 error_quit_pipe:
        lttng_pipe_destroy(ctx->consumer_wakeup_pipe);
@@ -1419,13 +1404,11 @@ void lttng_consumer_destroy(struct lttng_consumer_local_data *ctx)
        if (ret) {
                PERROR("close");
        }
-       utils_close_pipe(ctx->consumer_thread_pipe);
        utils_close_pipe(ctx->consumer_channel_pipe);
        lttng_pipe_destroy(ctx->consumer_data_pipe);
        lttng_pipe_destroy(ctx->consumer_metadata_pipe);
        lttng_pipe_destroy(ctx->consumer_wakeup_pipe);
        utils_close_pipe(ctx->consumer_should_quit);
-       utils_close_pipe(ctx->consumer_splice_metadata_pipe);
 
        unlink(ctx->consumer_command_sock_path);
        free(ctx);
@@ -1718,17 +1701,7 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
                        goto end;
                }
        }
-
-       /*
-        * Choose right pipe for splice. Metadata and trace data are handled by
-        * different threads hence the use of two pipes in order not to race or
-        * corrupt the written data.
-        */
-       if (stream->metadata_flag) {
-               splice_pipe = ctx->consumer_splice_metadata_pipe;
-       } else {
-               splice_pipe = ctx->consumer_thread_pipe;
-       }
+       splice_pipe = stream->splice_pipe;
 
        /* Write metadata stream id before payload */
        if (relayd) {
@@ -1834,7 +1807,8 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
                /* Splice data out */
                ret_splice = splice(splice_pipe[0], NULL, outfd, NULL,
                                ret_splice, SPLICE_F_MOVE | SPLICE_F_MORE);
-               DBG("Consumer splice pipe to file, ret %zd", ret_splice);
+               DBG("Consumer splice pipe to file (out_fd: %d), ret %zd",
+                               outfd, ret_splice);
                if (ret_splice < 0) {
                        ret = errno;
                        written = -ret;

diff --git a/src/common/consumer.h b/src/common/consumer.h
index 4ac823c017d03754ed545a9a1288df707b84778f..1e378f04ea631ea4387a1940c407599d19a63966 100644 (file)
--- a/src/common/consumer.h
+++ b/src/common/consumer.h
@@ -336,6 +336,11 @@ struct lttng_consumer_stream {
         */
        int index_fd;
 
+       /*
+        * Local pipe to extract data when using splice.
+        */
+       int splice_pipe[2];
+
        /*
         * Rendez-vous point between data and metadata stream in live mode.
         */
@@ -451,9 +456,7 @@ struct lttng_consumer_local_data {
        /* socket to exchange commands with sessiond */
        char *consumer_command_sock_path;
        /* communication with splice */
-       int consumer_thread_pipe[2];
        int consumer_channel_pipe[2];
-       int consumer_splice_metadata_pipe[2];
        /* Data stream poll thread pipe. To transfer data stream to the thread */
        struct lttng_pipe *consumer_data_pipe;
 

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index cbd1b5aac223962275b7be3472c7f498eb761077..6ec6acc6fa81465ea4c33a0f2de4b12ee64b42f2 100644 (file)
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -642,6 +642,10 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                switch (channel->output) {
                case CONSUMER_CHANNEL_SPLICE:
                        new_stream->output = LTTNG_EVENT_SPLICE;
+                       ret = utils_create_pipe(new_stream->splice_pipe);
+                       if (ret < 0) {
+                               goto end_nosignal;
+                       }
                        break;
                case CONSUMER_CHANNEL_MMAP:
                        new_stream->output = LTTNG_EVENT_MMAP;