Re: [Qemu-devel] [PATCH 1/3] qemu-io: Let -c abort raise any signal

[Markus Armbruster <armbru@redhat.com>]

Max Reitz <mreitz@redhat.com> writes:

> abort() has the sometimes undesirable side-effect of generating a core
> dump. If that is not needed, SIGKILL has the same effect of abruptly
> crash qemu; without a core dump.
>
> Therefore, this patch allows to use the qemu-io abort command to raise
> any signal.
>
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  qemu-io-cmds.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 56 insertions(+), 3 deletions(-)
>
> diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
> index d94fb1e..5d39cf4 100644
> --- a/qemu-io-cmds.c
> +++ b/qemu-io-cmds.c
> @@ -2036,18 +2036,71 @@ static const cmdinfo_t wait_break_cmd = {
>         .oneline        = "waits for the suspension of a request",
>  };
>  
> -static int abort_f(BlockDriverState *bs, int argc, char **argv)
> +
> +static void abort_help(void)
>  {
> -    abort();
> +    printf(
> +"\n"
> +" simulates a program crash\n"
> +"\n"
> +" Invokes abort(), or raise(signal) if a signal number is specified.\n"
> +" -S, -- number of the signal to raise()\n"
> +"\n");
>  }
>  
> +static int abort_f(BlockDriverState *bs, int argc, char **argv);
> +
>  static const cmdinfo_t abort_cmd = {
>         .name           = "abort",
>         .cfunc          = abort_f,
> +       .argmin         = 0,
> +       .argmax         = 2,
>         .flags          = CMD_NOFILE_OK,
> -       .oneline        = "simulate a program crash using abort(3)",
> +       .args           = "[-S signal]",
> +       .oneline        = "simulate a program crash",
> +       .help           = abort_help,
>  };

This overloads the abort command with a kill command.

Do we really need a way to send arbitrary signals?  If yes, shouldn't we
call it "kill" rather than "abort"?

I suspect fooling around with signals isn't necessary, and a simple
exit(1) would do.

>  
> +static int abort_f(BlockDriverState *bs, int argc, char **argv)
> +{
> +    int c;
> +    int sig = -1;
> +
> +    while ((c = getopt(argc, argv, "S:")) != EOF) {
> +        switch (c) {
> +            case 'S':
> +                sig = cvtnum(optarg);
> +                if (sig < 0) {
> +                    printf("non-numeric signal number argument -- %s\n", optarg);
> +                    return 0;
> +                }
> +                break;
> +
> +            default:
> +                return qemuio_command_usage(&abort_cmd);
> +        }
> +    }
> +
> +    if (optind != argc) {
> +        return qemuio_command_usage(&abort_cmd);
> +    }
> +
> +    if (sig < 0) {
> +        abort();
> +    } else {
> +        /* While abort() does flush all open streams, using raise() to kill this
> +         * process does not necessarily. At least stdout and stderr (although
> +         * the latter should be non-buffered anyway) should be flushed, though.
> +         */
> +        fflush(stdout);
> +        fflush(stderr);

Without -S, we flush all streams.  With -S, we flush only stdout and
stderr.  The inconsistency is ugly.  Could be avoided with fcloseall(),
except it's a GNU extension.  Or drop the non-signal path entirely, and
raise(SIGABRT) instead of abort().

> +
> +        raise(sig);
> +        /* raise() may return */
> +        return 0;
> +    }
> +}
> +
>  static void sleep_cb(void *opaque)
>  {
>      bool *expired = opaque;