Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Ideally, we want to atomically flush and disable the tasklet before
> resetting the GPU. At present, we rely on being the only part to touch
> our tasklet and serialisation of the reset process to ensure that we can
> suspend the tasklet from the mix of reset/wedge pathways. In this patch,
> we move the tasklet abuse into its own function and tweak it such that
> we only do a synchronous operation the first time it is disabled around
> the reset. This allows us to avoid the sync inside a softirq context in
> subsequent patches.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
> CC: Michel Thierry <michel.thierry@xxxxxxxxx>
> Cc: Jeff McGee <jeff.mcgee@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_lrc.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index bbcc6439a2a1..d5640f3d5276 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1754,6 +1754,16 @@ static int gen9_init_render_ring(struct intel_engine_cs *engine)
> return init_workarounds_ring(engine);
> }
>
> +static void tasklet_kill_and_disable(struct tasklet_struct *t)
> +{
> + if (!atomic_read(&t->count))
> + tasklet_kill(t);
> +
> + if (atomic_inc_return(&t->count) == 1)
> + tasklet_unlock_wait(t);
You would spin only on the first try regardless. Is this
just to prevent one extra spinlock on reset path?
-Mika
> + smp_mb();
> +}
> +
> static struct i915_request *
> execlists_reset_prepare(struct intel_engine_cs *engine)
> {
> @@ -1778,9 +1788,7 @@ execlists_reset_prepare(struct intel_engine_cs *engine)
> * common case of recursively being called from set-wedged from inside
> * i915_reset.
> */
> - if (!atomic_read(&execlists->tasklet.count))
> - tasklet_kill(&execlists->tasklet);
> - tasklet_disable(&execlists->tasklet);
> + tasklet_kill_and_disable(&execlists->tasklet);
>
> /*
> * We want to flush the pending context switches, having disabled
> --
> 2.17.0
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