On Thu, Jun 09, 2016 at 12:05:28PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
>
> Signalling doesn't need to be enabled at sync_file creation, it is only
> required if userspace waiting the fence to signal through poll().
>
> Thus we delay fence_add_callback() until poll is called. It only adds the
> callback the first time poll() is called. This avoid re-adding the same
> callback multiple times.
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> ---
> drivers/dma-buf/sync_file.c | 36 +++++++++++++++++++++++-------------
> include/linux/fence.h | 12 ++++++++++++
> 2 files changed, 35 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
> index 00e9186..59f3445 100644
> --- a/drivers/dma-buf/sync_file.c
> +++ b/drivers/dma-buf/sync_file.c
> @@ -91,9 +91,7 @@ struct sync_file *sync_file_create(struct fence *fence)
>
> sync_file->cbs[0].fence = fence;
> sync_file->cbs[0].sync_file = sync_file;
> - if (fence_add_callback(fence, &sync_file->cbs[0].cb,
> - fence_check_cb_func))
> - atomic_dec(&sync_file->status);
> + INIT_LIST_HEAD(&sync_file->cbs[0].cb.node);
>
> sync_file_debug_add(sync_file);
> return sync_file;
> @@ -130,8 +128,7 @@ static void sync_file_add_pt(struct sync_file *sync_file, int *i,
> sync_file->cbs[*i].fence = fence;
> sync_file->cbs[*i].sync_file = sync_file;
>
> - if (!fence_add_callback(fence, &sync_file->cbs[*i].cb,
> - fence_check_cb_func)) {
> + if (!fence_is_signaled(fence)) {
> fence_get(fence);
> (*i)++;
> }
> @@ -212,11 +209,8 @@ static void sync_file_free(struct kref *kref)
> kref);
> int i;
>
> - for (i = 0; i < sync_file->num_fences; ++i) {
> - fence_remove_callback(sync_file->cbs[i].fence,
> - &sync_file->cbs[i].cb);
> + for (i = 0; i < sync_file->num_fences; ++i)
> fence_put(sync_file->cbs[i].fence);
> - }
>
> sync_file_debug_remove(sync_file);
> kfree(sync_file);
> @@ -233,17 +227,33 @@ static int sync_file_release(struct inode *inode, struct file *file)
> static unsigned int sync_file_poll(struct file *file, poll_table *wait)
> {
> struct sync_file *sync_file = file->private_data;
> - int status;
> + int status, i;
>
> poll_wait(file, &sync_file->wq, wait);
>
> + for (i = 0 ; i < sync_file->num_fences ; i++) {
> + if (fence_is_enabled(sync_file->cbs[i].fence))
If some other sync_file (or anyone else really) added enabling, then
you'll miss adding a callback. I don't think this check here works. You
probably also need more testcases in the debugfs-based tests if this falls
through the cracks ;-)
-Daniel
> + continue;
> +
> + if (fence_add_callback(sync_file->cbs[i].fence,
> + &sync_file->cbs[i].cb,
> + fence_check_cb_func))
> + atomic_dec(&sync_file->status);
> + }
> +
> status = atomic_read(&sync_file->status);
>
> - if (!status)
> - return POLLIN;
> + if (status > 0)
> + return 0;
> +
> + for (i = 0 ; i < sync_file->num_fences ; i++)
> + fence_remove_callback(sync_file->cbs[i].fence,
> + &sync_file->cbs[i].cb);
> +
> if (status < 0)
> return POLLERR;
> - return 0;
> +
> + return POLLIN;
> }
>
> static long sync_file_ioctl_merge(struct sync_file *sync_file,
> diff --git a/include/linux/fence.h b/include/linux/fence.h
> index 523ea3f..95a70b2 100644
> --- a/include/linux/fence.h
> +++ b/include/linux/fence.h
> @@ -283,6 +283,18 @@ fence_is_signaled(struct fence *fence)
> }
>
> /**
> + * fence_is_enabled - return an indication if signalling is enabled
> + * @fence: [in] the fence to check
> + *
> + * Returns true if signalling was already enabled, false if not.
> + */
> +static inline bool
> +fence_is_enabled(struct fence *fence)
> +{
> + return test_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
> +}
> +
> +/**
> * fence_is_later - return if f1 is chronologically later than f2
> * @f1: [in] the first fence from the same context
> * @f2: [in] the second fence from the same context
> --
> 2.5.5
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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