Hi Chris,
On 4 January 2017 at 19:42, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> The dma_fence.error field (formerly known as dma_fence.status) is an
> optional field that may be set by drivers before calling
> dma_fence_signal(). The field can be used to indicate that the fence was
> completed in err rather than with success, and is visible to other
> consumers of the fence and to userspace via sync_file.
>
> This patch renames the field from status to error so that its meaning is
> hopefully more clear (and distinct from dma_fence_get_status() which is
> a composite between the error state and signal state) and adds a helper
> that validates the preconditions of when it is suitable to adjust the
> error field.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/dma-buf/dma-fence.c | 2 +-
> include/linux/dma-fence.h | 30 +++++++++++++++++++++++++-----
> 2 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 7d936d19e659..ee82f36cb25e 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -559,7 +559,7 @@ dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
> fence->context = context;
> fence->seqno = seqno;
> fence->flags = 0UL;
> - fence->status = 0;
> + fence->error = 0;
>
> trace_dma_fence_init(fence);
> }
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 19f7af905182..6048fa404e57 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -47,7 +47,7 @@ struct dma_fence_cb;
> * can be compared to decide which fence would be signaled later.
> * @flags: A mask of DMA_FENCE_FLAG_* defined below
> * @timestamp: Timestamp when the fence was signaled.
> - * @status: Optional, only valid if < 0, must be set before calling
> + * @error: Optional, only valid if < 0, must be set before calling
> * dma_fence_signal, indicates that the fence has completed with an error.
> *
> * the flags member must be manipulated and read using the appropriate
> @@ -79,7 +79,7 @@ struct dma_fence {
> unsigned seqno;
> unsigned long flags;
> ktime_t timestamp;
> - int status;
> + int error;
> };
>
> enum dma_fence_flag_bits {
> @@ -133,7 +133,7 @@ struct dma_fence_cb {
> * or some failure occurred that made it impossible to enable
> * signaling. True indicates successful enabling.
> *
> - * fence->status may be set in enable_signaling, but only when false is
> + * fence->error may be set in enable_signaling, but only when false is
> * returned.
> *
> * Calling dma_fence_signal before enable_signaling is called allows
> @@ -145,7 +145,7 @@ struct dma_fence_cb {
> * the second time will be a noop since it was already signaled.
> *
> * Notes on signaled:
> - * May set fence->status if returning true.
> + * May set fence->error if returning true.
> *
> * Notes on wait:
> * Must not be NULL, set to dma_fence_default_wait for default implementation.
> @@ -395,13 +395,33 @@ static inline struct dma_fence *dma_fence_later(struct dma_fence *f1,
> static inline int dma_fence_get_status_locked(struct dma_fence *fence)
> {
> if (dma_fence_is_signaled_locked(fence))
> - return fence->status < 0 ? fence->status : 1;
> + return fence->error ?: 1;
> else
> return 0;
> }
>
> int dma_fence_get_status(struct dma_fence *fence);
>
> +/**
> + * dma_fence_set_error - flag an error condition on the fence
> + * @fence: [in] the dma_fence
> + * @error: [in] the error to store
> + *
> + * Drivers can supply an optional error status condition before they signal
> + * the fence, to indicate that the fence was completed due to an error
> + * rather than success. This must be set before signaling (so that the value
> + * is visible before any waiters on the signal callback are woken). This
> + * helper exists to help catching erroneous setting of #dma_fence.error.
> + */
> +static inline void dma_fence_set_error(struct dma_fence *fence,
> + int error)
> +{
> + BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
> + BUG_ON(error >= 0 || error < -MAX_ERRNO);
> +
> + fence->error = error;
> +}
Sorry I missed this earlier, but are you sure you want to use a BUG_ON
here, and not a WARN_ON?
> +
> signed long dma_fence_wait_timeout(struct dma_fence *,
> bool intr, signed long timeout);
> signed long dma_fence_wait_any_timeout(struct dma_fence **fences,
> --
> 2.11.0
>
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Best,
Sumit.
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