I tried to sort through this, but got a bit lost. Possible solution at the
end of the email.
tl;dr:
# blktrace -o - /dev/sda /dev/sdb /dev/sdc
has to be SIGKILLed if BLKTRACESETUP fails for any or all of the devices
listed. (I simulated this by just catching one of the devices in
setup_buts(), skipping the ioctl, and doing ret++).
This seems to be because with "-o -" on the command line, use_tracer_devpaths()
sees piped_output set, so we call process_trace_bufs which ends up waiting on
(!done) and "done" is never set. i.e.
atexit(exit_tracing)
wait_tracers
if (use_tracer_devpaths()) // true because "-o -"
process_trace_bufs
while (wait_empty_entries())
wait_empty_entries
while (!done ... )
<loop forever>
I think this can be avoided by just setting "done = 1" before returning
when setup_buts() fails in run_tracers(), but I'm not sure if that's the
right approach. Thoughts?
Thanks,
-Eric
diff --git a/blktrace.c b/blktrace.c
index 3444fbb..038b2cb 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -2684,8 +2684,10 @@ static int run_tracers(void)
if (net_mode == Net_client)
printf("blktrace: connecting to %s\n", hostname);
- if (setup_buts())
+ if (setup_buts()) {
+ done = 1;
return 1;
+ }
if (use_tracer_devpaths()) {
if (setup_tracer_devpaths())
