Signal-based file switching support for relay/ring buffer.

* runtime/staprun/relay.c (switch_outfile): New function for file switching.
  (reader_thread): Don't assign empty_handler to SIGUSR2, and switch output
  file when receiving signal(SIGUSR2) on ppoll.
  (switchfile_handler): Send SIGUSR2 signal to reader threads for file
  switching.
  (init_relayfs): Assign switchfile_handler to SIGUSR2.
* staprun.1.in: Add FILE SWITCHING BY SIGNAL section.

1 files changed, 33 insertions, 0 deletions

diff --git a/staprun.8.in b/staprun.8.in
index 5fe2e7fa..5bf2ec61 100644
--- a/staprun.8.in
+++ b/staprun.8.in
@@ -138,6 +138,39 @@ To reattach to a kernel module, the
 .I staprun
 .B \-A
 option would be used.
+
+.SH FILE SWITCHING BY SIGNAL
+After the
+.I staprun
+launched the
+.I stapio
+, users can command it to switch output file to next file when it
+outputs to file(s) (running staprun with
+.B \-o
+option) by sending a
+.B SIGUSR2
+signal to the
+.I stapio
+process. When it receives SIGUSR2, it will switch output file to
+new file with suffix 
+.I .N
+where N is the sequential number.
+For example,
+.PP
+\& $ staprun \-o foo ...
+.PP
+outputs trace logs to 
+.I foo
+and if it receives
+.B SIGUSR2
+signal, it switches output to
+.I foo.1
+file. And receiving
+.B SIGUSR2
+again, it switches to 
+.I foo.2
+file.
+
 .SH SAFETY AND SECURITY
 Systemtap is an administrative tool.  It exposes kernel internal data
 structures and potentially private user information.  See the