[Intel-gfx] [IGT PATCH 1/2] aux: Suspend signal helper for shell commands

[Daniel Vetter]

On Thu, Oct 12, 2017 at 04:22:06PM +0300, Imre Deak wrote:
> The clone() system call with a larger executable (like /bin/sh) may have
> difficulty to make progress on some platforms if interrupted frequently.
> So suspend the signal helper process for the duration of the syscall.
> This is needed to solve an actual problem by the next patch.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter at intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>

Your patch prefix is wrong, which means CI wont' pick this up. Please
resubmit with i-g-t as patch thing per our CONTRIBUTING file.

Thanks, Daniel

PS: Yes we'll soon have a separate mailing list for igt to avoid this kind
of fun.
-Daniel

> ---
>  lib/igt_aux.c  | 38 ++++++++++++++++++++++++++++++++++++++
>  lib/igt_aux.h  |  2 ++
>  lib/igt_core.c |  9 +++++++++
>  3 files changed, 49 insertions(+)
> 
> diff --git a/lib/igt_aux.c b/lib/igt_aux.c
> index fa6594c3..36dfab43 100644
> --- a/lib/igt_aux.c
> +++ b/lib/igt_aux.c
> @@ -350,6 +350,44 @@ void igt_stop_signal_helper(void)
>  	sig_stat = 0;
>  }
>  
> +/**
> + * igt_suspend_signal_helper:
> + *
> + * Suspends the child process spawned with igt_fork_signal_helper().
> + *
> + * This should be called before code that has difficulty to make progress if
> + * interrupted frequently, like the clone() syscall spawning a large
> + * executable.
> + */
> +void igt_suspend_signal_helper(void)
> +{
> +	int status;
> +
> +	if (!signal_helper.running)
> +		return;
> +
> +	kill(signal_helper.pid, SIGSTOP);
> +	while (waitpid(signal_helper.pid, &status, WUNTRACED) == -1 &&
> +	       errno == EINTR)
> +		;
> +}
> +
> +/**
> + * igt_suspend_signal_helper:
> + *
> + * Resumes the child process spawned with igt_fork_signal_helper().
> + *
> + * This should be paired with igt_suspend_signal_helper() and called after the
> + * problematic code sensitive to signals.
> + */
> +void igt_resume_signal_helper(void)
> +{
> +	if (!signal_helper.running)
> +		return;
> +
> +	kill(signal_helper.pid, SIGCONT);
> +}
> +
>  static struct igt_helper_process shrink_helper;
>  static void __attribute__((noreturn)) shrink_helper_process(int fd, pid_t pid)
>  {
> diff --git a/lib/igt_aux.h b/lib/igt_aux.h
> index 499a1679..688ad1b8 100644
> --- a/lib/igt_aux.h
> +++ b/lib/igt_aux.h
> @@ -55,6 +55,8 @@ extern int num_trash_bos;
>  /* generally useful helpers */
>  void igt_fork_signal_helper(void);
>  void igt_stop_signal_helper(void);
> +void igt_suspend_signal_helper(void);
> +void igt_resume_signal_helper(void);
>  
>  void igt_fork_shrink_helper(int fd);
>  void igt_stop_shrink_helper(void);
> diff --git a/lib/igt_core.c b/lib/igt_core.c
> index 950ea9b0..ea4b5fa6 100644
> --- a/lib/igt_core.c
> +++ b/lib/igt_core.c
> @@ -2282,6 +2282,13 @@ int igt_system(const char *command)
>  	if (pipe(errpipe) < 0)
>  		goto err;
>  
> +	/*
> +	 * The clone() system call forking a large executable has difficulty
> +	 * to make progress if interrupted too frequently, so suspend it for
> +	 * the time of the syscall.
> +	 */
> +	igt_suspend_signal_helper();
> +
>  	igt_fork_helper(&process) {
>  		close(outpipe[0]);
>  		close(errpipe[0]);
> @@ -2298,6 +2305,8 @@ int igt_system(const char *command)
>  		exit(EXIT_FAILURE);
>  	}
>  
> +	igt_resume_signal_helper();
> +
>  	close(outpipe[1]);
>  	close(errpipe[1]);
>  
> -- 
> 2.13.2
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch