Re: [PATCH V1 12/32] vl: pause option

[Alex Bennée]

Steve Sistare <steven.sistare@oracle.com> writes:

> Provide the -pause command-line parameter and the QEMU_PAUSE environment
> variable to briefly pause QEMU in main and allow a developer to attach gdb.
> Useful when the developer does not invoke QEMU directly, such as when using
> libvirt.

How does this differ from -S?

>
> Usage:
>   qemu -pause <seconds>
>   or
>   export QEMU_PAUSE=<seconds>
>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>  qemu-options.hx |  9 +++++++++
>  softmmu/vl.c    | 15 ++++++++++++++-
>  2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 708583b..8505cf2 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3668,6 +3668,15 @@ SRST
>      option is experimental.
>  ERST
>  
> +DEF("pause", HAS_ARG, QEMU_OPTION_pause, \
> +    "-pause secs    Pause for secs seconds on entry to main.\n", 
> QEMU_ARCH_ALL)
> +
> +SRST
> +``--pause secs``
> +    Pause for a number of seconds on entry to main.  Useful for attaching
> +    a debugger after QEMU has been launched by some other entity.
> +ERST
> +

It seems like having an option to race with the debugger is just asking
for trouble.

>  DEF("S", 0, QEMU_OPTION_S, \
>      "-S              freeze CPU at startup (use 'c' to start execution)\n",
>      QEMU_ARCH_ALL)
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index 8478778..951994f 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2844,7 +2844,7 @@ static void create_default_memdev(MachineState *ms, 
> const char *path)
>  
>  void qemu_init(int argc, char **argv, char **envp)
>  {
> -    int i;
> +    int i, seconds;
>      int snapshot, linux_boot;
>      const char *initrd_filename;
>      const char *kernel_filename, *kernel_cmdline;
> @@ -2882,6 +2882,13 @@ void qemu_init(int argc, char **argv, char **envp)
>      QemuPluginList plugin_list = QTAILQ_HEAD_INITIALIZER(plugin_list);
>      int mem_prealloc = 0; /* force preallocation of physical target memory */
>  
> +    if (getenv("QEMU_PAUSE")) {
> +        seconds = atoi(getenv("QEMU_PAUSE"));
> +        printf("Pausing %d seconds for debugger. QEMU PID is %d\n",
> +               seconds, getpid());
> +        sleep(seconds);
> +    }
> +
>      os_set_line_buffering();
>  
>      error_init(argv[0]);
> @@ -3204,6 +3211,12 @@ void qemu_init(int argc, char **argv, char **envp)
>              case QEMU_OPTION_gdb:
>                  add_device_config(DEV_GDB, optarg);
>                  break;
> +            case QEMU_OPTION_pause:
> +                seconds = atoi(optarg);
> +                printf("Pausing %d seconds for debugger. QEMU PID is %d\n",
> +                            seconds, getpid());
> +                sleep(seconds);
> +                break;
>              case QEMU_OPTION_L:
>                  if (is_help_option(optarg)) {
>                      list_data_dirs = true;


-- 
Alex Bennée