logwrapper: prevent logwrap from hanging when child dies

Sometimes the read on the PTY can wait indefinitely if the child
dies. By using a poll statement that monitors both the output
of the child and its state we prevent this from happening.

Change-Id: I51d5556c66f039bca673145ca72db262977e1689

1 files changed, 23 insertions, 1 deletions

diff --git a/logwrapper/include/logwrap/logwrap.h b/logwrapper/include/logwrap/logwrap.h
index a58f238..722dda2 100644
--- a/logwrapper/include/logwrap/logwrap.h
+++ b/logwrapper/include/logwrap/logwrap.h
@@ -20,7 +20,29 @@
 
 __BEGIN_DECLS
 
-int logwrap(int argc, char* argv[], int *chld_sts);
+/*
+ * Run a command while logging its stdout and stderr
+ *
+ * WARNING: while this function is running it will clear all SIGCHLD handlers
+ * if you rely on SIGCHLD in the caller there is a chance zombies will be
+ * created if you're not calling waitpid after calling this. This function will
+ * log a warning when it clears SIGCHLD for processes other than the child it
+ * created.
+ *
+ * Arguments:
+ *   argc:   the number of elements in argv
+ *   argv:   an array of strings containing the command to be executed and its
+ *           arguments as separate strings. argv does not need to be
+ *           NULL-terminated
+ *   status: the equivalent child status as populated by wait(status). This
+ *           value is only valid when logwrap successfully completes
+ *
+ * Return value:
+ *   0 when logwrap successfully run the child process and captured its status
+ *   -1 when an internal error occurred
+ *
+ */
+int logwrap(int argc, char* argv[], int *status);
 
 __END_DECLS