Quoting Imre Deak (2017-10-12 14:22:06)
> 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@xxxxxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> 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.
* igt_resume_signal_helper() must be called after the critical section
* to restart interruptions for the test.
> + */
> +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:
igt_resume_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);
> +}
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris
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