From 9aed43774a511ae9b2458e474d0f2efe5bfa871e Mon Sep 17 00:00:00 2001 From: =?utf8?q?J=C3=A9r=C3=A9mie=20Galarneau?= Date: Tue, 12 Jun 2018 17:16:32 -0400 Subject: [PATCH 1/1] Document the contents of the shm_path fields of the ust session registry MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Signed-off-by: Jérémie Galarneau --- src/bin/lttng-sessiond/ust-registry.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/src/bin/lttng-sessiond/ust-registry.h b/src/bin/lttng-sessiond/ust-registry.h index 414975caf..2940ab7ac 100644 --- a/src/bin/lttng-sessiond/ust-registry.h +++ b/src/bin/lttng-sessiond/ust-registry.h @@ -71,6 +71,32 @@ struct ust_registry_session { /* Current version of the metadata. */ uint64_t metadata_version; + /* + * Those fields are only used when a session is created with + * the --shm-path option. In this case, the metadata is output + * twice: once to the consumer, as ususal, but a second time + * also in the shm path directly. This is done so that a copy + * of the metadata that is as fresh as possible is available + * on the event of a crash. + * + * root_shm_path contains the shm-path provided by the user, along with + * the session's name and timestamp: + * e.g. /tmp/my_shm/my_session-20180612-135822 + * + * shm_path contains the full path of the memory buffers: + * e.g. /tmp/my_shm/my_session-20180612-135822/ust/uid/1000/64-bit + * + * metadata_path contains the full path to the metadata file that + * is kept for the "crash buffer" extraction: + * e.g. /tmp/my_shm/my_session-20180612-135822/ust/uid/1000/64-bit/metadata + * + * Note that this is not the trace's final metadata file. It is + * only meant to be used to read the contents of the ring buffers + * in the event of a crash. + * + * metadata_fd is a file descriptor that points to the file at + * 'metadata_path'. + */ char root_shm_path[PATH_MAX]; char shm_path[PATH_MAX]; char metadata_path[PATH_MAX]; -- 2.34.1