[Intel-gfx] [PATCH igt] lib: Always enable ftrace-dump-on-oops

[Petri Latvala]

On Wed, Nov 08, 2017 at 12:18:40PM +0000, Chris Wilson wrote:
> Some debugging information is too voluminous to enable by default, yet
> may be invaluable when it comes to post-mortem debugging. trace_printk()
> provides the facility for the trace ringbuffer to be dumped on oops,
> this way we can cheaply spam the debug log and only present it in case
> of emergency.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  lib/igt_core.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/lib/igt_core.c b/lib/igt_core.c
> index 538a4472..ba4622d6 100644
> --- a/lib/igt_core.c
> +++ b/lib/igt_core.c
> @@ -561,6 +561,28 @@ static void low_mem_killer_disable(bool disable)
>  	chmod(adj_fname, buf.st_mode);
>  }
>  
> +/*
> + * If the test takes out the machine, in addition to the usual dmesg
> + * spam, the kernel may also emit a "death rattle" -- extra debug
> + * information that is overkill for normal successful tests, but
> + * vital for post-mortem analysis.
> + */
> +static void ftrace_dump_on_oops(bool enable)
> +{
> +	int fd;
> +
> +	fd = open("/proc/sys/kernel/ftrace_dump_on_oops", O_WRONLY);
> +	if (fd < 0)
> +		return;
> +
> +	/*
> +	 * If we fail, we do not get the death rattle we wish, but we
> +	 * still want to run the tests anyway.
> +	 */
> +	igt_ignore_warn(write(fd, enable ? "1\n" : "0\n", 2));
> +	close(fd);
> +}
> +
>  bool igt_exit_called;
>  static void common_exit_handler(int sig)
>  {
> @@ -858,6 +880,7 @@ out:
>  		sync();
>  		oom_adjust_for_doom();
>  		low_mem_killer_disable(true);
> +		ftrace_dump_on_oops(true);


Is there a call to disable it too? Or rather, restore the value that
was there before executing a test.


--
Petri Latvala