trace2: add trace2_child_ready() to report on background children

Create "child_ready" event to capture the state of a child process
created in the background.

When a child command is started a "child_start" event is generated in
the Trace2 log.  For normal synchronous children, a "child_exit" event
is later generated when the child exits or is terminated.  The two events
include information, such as the "child_id" and "pid", to allow post
analysis to match-up the command line and exit status.

When a child is started in the background (and may outlive the parent
process), it is not possible for the parent to emit a "child_exit"
event.  Create a new "child_ready" event to indicate whether the
child was successfully started.  Also include the "child_id" and "pid"
to allow similar post processing.

This will be used in a later commit with the new "start_bg_command()".

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/trace2/tr2_tgt.h b/trace2/tr2_tgt.h
index 1f66fd6573..65f94e1574 100644
--- a/trace2/tr2_tgt.h
+++ b/trace2/tr2_tgt.h
@@ -45,6 +45,10 @@ typedef void(tr2_tgt_evt_child_exit_fl_t)(const char *file, int line,
 					  uint64_t us_elapsed_absolute, int cid,
 					  int pid, int code,
 					  uint64_t us_elapsed_child);
+typedef void(tr2_tgt_evt_child_ready_fl_t)(const char *file, int line,
+					   uint64_t us_elapsed_absolute,
+					   int cid, int pid, const char *ready,
+					   uint64_t us_elapsed_child);
 
 typedef void(tr2_tgt_evt_thread_start_fl_t)(const char *file, int line,
 					    uint64_t us_elapsed_absolute);
@@ -116,6 +120,7 @@ struct tr2_tgt {
 	tr2_tgt_evt_alias_fl_t                  *pfn_alias_fl;
 	tr2_tgt_evt_child_start_fl_t            *pfn_child_start_fl;
 	tr2_tgt_evt_child_exit_fl_t             *pfn_child_exit_fl;
+	tr2_tgt_evt_child_ready_fl_t            *pfn_child_ready_fl;
 	tr2_tgt_evt_thread_start_fl_t           *pfn_thread_start_fl;
 	tr2_tgt_evt_thread_exit_fl_t            *pfn_thread_exit_fl;
 	tr2_tgt_evt_exec_fl_t                   *pfn_exec_fl;