Re: [PATCH i-g-t] Add dmesg capture and dumping to tests and a test for it.

[Chris Wilson <chris@chris-wilson.co.uk>]

On Mon, Nov 16, 2015 at 03:22:23PM +0200, Joonas Lahtinen wrote:
> Cc: Thomas Wood <thomas.wood@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Damien Lespiau <damien.lespiau@intel.com>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
>  lib/igt_core.c         | 113 ++++++++++++++++++++++++++++++++++++++++++++++---
>  tests/Makefile.sources |   1 +
>  tests/igt_capture.c    |  93 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 200 insertions(+), 7 deletions(-)
>  create mode 100644 tests/igt_capture.c
> 
> diff --git a/lib/igt_core.c b/lib/igt_core.c
> index 04a0ab2..e73175a 100644
> --- a/lib/igt_core.c
> +++ b/lib/igt_core.c
> @@ -211,6 +211,8 @@
>   * "--help" command line option.
>   */
>  
> +#define IGT_KMSG_CAPTURE_DUMP_BUF_SIZE		4096
> +
>  static unsigned int exit_handler_count;
>  const char *igt_interactive_debug;
>  
> @@ -247,6 +249,10 @@ enum {
>  static int igt_exitcode = IGT_EXIT_SUCCESS;
>  static const char *command_str;
>  
> +static int igt_kmsg_capture_fd;
> +static char* igt_kmsg_capture_dump_buf;
> +static pthread_mutex_t kmsg_mutex = PTHREAD_MUTEX_INITIALIZER;
> +
>  static char* igt_log_domain_filter;
>  static struct {
>  	char *entries[256];
> @@ -312,6 +318,71 @@ static void _igt_log_buffer_dump(void)
>  	pthread_mutex_unlock(&log_buffer_mutex);
>  }
>  
> +static void _igt_kmsg_capture_reset(void)
> +{
> +	if (igt_kmsg_capture_fd == -1)
> +		return;
> +
> +	pthread_mutex_lock(&kmsg_mutex);
> +
> +	lseek(igt_kmsg_capture_fd, 0, SEEK_END);
> +
> +	pthread_mutex_unlock(&kmsg_mutex);
> +}

Since close() is signal-safe, you can avoid the mutex (which is not
signal-safe, but we can hope not to generate reentrancy here!) by
opening /dev/kmsg for each subtest, and close it again in
exit_subtest().

Note that we also want to detect dmesg spew during igt when the tests
report all is well. Having the full log associated with a fail,
preferrably with --debug is good, but filtering the <prio> for errors is
also useful.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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