Quoting Tvrtko Ursulin (2018-01-15 10:08:01)
>
> On 15/01/2018 09:06, Chris Wilson wrote:
> > As the timeout mechanism has grown more and more complicated, using
> > multiple deferred tasks and more than doubling the size of our struct,
> > split the two implementations to streamline the simpler no-timeout
> > callback variant.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_sw_fence.c | 61 +++++++++++++++++++++++-------------
> > 1 file changed, 40 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
> > index 13021326d777..1de5173e53a2 100644
> > --- a/drivers/gpu/drm/i915/i915_sw_fence.c
> > +++ b/drivers/gpu/drm/i915/i915_sw_fence.c
> > @@ -365,18 +365,31 @@ int i915_sw_fence_await_sw_fence_gfp(struct i915_sw_fence *fence,
> > struct i915_sw_dma_fence_cb {
> > struct dma_fence_cb base;
> > struct i915_sw_fence *fence;
> > +};
> > +
> > +struct i915_sw_dma_fence_cb_timer {
> > + struct i915_sw_dma_fence_cb base;
> > struct dma_fence *dma;
> > struct timer_list timer;
> > struct irq_work work;
> > struct rcu_head rcu;
> > };
> >
> > +static void dma_i915_sw_fence_wake(struct dma_fence *dma,
> > + struct dma_fence_cb *data)
> > +{
> > + struct i915_sw_dma_fence_cb *cb = container_of(data, typeof(*cb), base);
> > +
> > + i915_sw_fence_complete(cb->fence);
> > + kfree(cb);
> > +}
> > +
> > static void timer_i915_sw_fence_wake(struct timer_list *t)
> > {
> > - struct i915_sw_dma_fence_cb *cb = from_timer(cb, t, timer);
> > + struct i915_sw_dma_fence_cb_timer *cb = from_timer(cb, t, timer);
> > struct i915_sw_fence *fence;
> >
> > - fence = xchg(&cb->fence, NULL);
> > + fence = xchg(&cb->base.fence, NULL);
> > if (!fence)
> > return;
> >
> > @@ -388,27 +401,24 @@ static void timer_i915_sw_fence_wake(struct timer_list *t)
> > i915_sw_fence_complete(fence);
> > }
> >
> > -static void dma_i915_sw_fence_wake(struct dma_fence *dma,
> > - struct dma_fence_cb *data)
> > +static void dma_i915_sw_fence_wake_timer(struct dma_fence *dma,
> > + struct dma_fence_cb *data)
> > {
> > - struct i915_sw_dma_fence_cb *cb = container_of(data, typeof(*cb), base);
> > + struct i915_sw_dma_fence_cb_timer *cb =
> > + container_of(data, typeof(*cb), base.base);
> > struct i915_sw_fence *fence;
> >
> > - fence = xchg(&cb->fence, NULL);
> > + fence = xchg(&cb->base.fence, NULL);
> > if (fence)
> > i915_sw_fence_complete(fence);
> >
> > - if (cb->dma) {
> > - irq_work_queue(&cb->work);
> > - return;
> > - }
> > -
> > - kfree(cb);
> > + irq_work_queue(&cb->work);
> > }
> >
> > static void irq_i915_sw_fence_work(struct irq_work *wrk)
> > {
> > - struct i915_sw_dma_fence_cb *cb = container_of(wrk, typeof(*cb), work);
> > + struct i915_sw_dma_fence_cb_timer *cb =
> > + container_of(wrk, typeof(*cb), work);
> >
> > del_timer_sync(&cb->timer);
> > dma_fence_put(cb->dma);
> > @@ -422,6 +432,7 @@ int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
> > gfp_t gfp)
> > {
> > struct i915_sw_dma_fence_cb *cb;
> > + dma_fence_func_t func;
> > int ret;
> >
> > debug_fence_assert(fence);
> > @@ -430,7 +441,10 @@ int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
> > if (dma_fence_is_signaled(dma))
> > return 0;
> >
> > - cb = kmalloc(sizeof(*cb), gfp);
> > + cb = kmalloc(timeout ?
> > + sizeof(struct i915_sw_dma_fence_cb_timer) :
> > + sizeof(struct i915_sw_dma_fence_cb),
> > + gfp);
> > if (!cb) {
> > if (!gfpflags_allow_blocking(gfp))
> > return -ENOMEM;
> > @@ -441,21 +455,26 @@ int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
> > cb->fence = fence;
> > i915_sw_fence_await(fence);
> >
> > - cb->dma = NULL;
> > + func = dma_i915_sw_fence_wake;
> > if (timeout) {
> > - cb->dma = dma_fence_get(dma);
> > - init_irq_work(&cb->work, irq_i915_sw_fence_work);
> > + struct i915_sw_dma_fence_cb_timer *timer =
> > + container_of(cb, typeof(*timer), base);
> >
> > - timer_setup(&cb->timer,
> > + timer->dma = dma_fence_get(dma);
> > + init_irq_work(&timer->work, irq_i915_sw_fence_work);
> > +
> > + timer_setup(&timer->timer,
> > timer_i915_sw_fence_wake, TIMER_IRQSAFE);
> > - mod_timer(&cb->timer, round_jiffies_up(jiffies + timeout));
> > + mod_timer(&timer->timer, round_jiffies_up(jiffies + timeout));
> > +
> > + func = dma_i915_sw_fence_wake_timer;
> > }
> >
> > - ret = dma_fence_add_callback(dma, &cb->base, dma_i915_sw_fence_wake);
> > + ret = dma_fence_add_callback(dma, &cb->base, func);
> > if (ret == 0) {
> > ret = 1;
> > } else {
> > - dma_i915_sw_fence_wake(dma, &cb->base);
> > + func(dma, &cb->base);
> > if (ret == -ENOENT) /* fence already signaled */
> > ret = 0;
> > }
> >
>
> If it compiles, and works, assuming we have tests cases which exercise
> both paths, then it is obviously fine.
The no-timeout variants are using for inter-engine signaling, the
timeout variant for external fences and KMS. Yes, both are covered,
though only the no-timeout variants are really stressed to see how
timeouts are handled (i.e. GPU hang and reset). The actual timeout
fences are only stressed in a token effort, and hard to distinguish from
the multiple similar timeout mechanisms spread around the code.
-Chris
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