Eric Sandeen <sandeen@xxxxxxxxxxx> writes:
> 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?
I think that looks ok. I think we probably should also set 'done = 1' if
setup_tracer_devpaths() fails as well.
-Jeff
>
> 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())
>
>
