Re: [PATCH 15/16] drm/etnaviv: use ktime_t for timeouts

Lucas Stach
2019-11-08T23:03:52Z

Am Freitag, den 08.11.2019, 22:32 +0100 schrieb Arnd Bergmann:
> struct timespec is being removed from the kernel because it often leads
> to code that is not y2038-safe.
>
> In the etnaviv driver, monotonic timestamps are used, which do not suffer
> from overflow, but using ktime_t still leads to better code overall.
>
> The conversion is straightforward for the most part, except for
> etnaviv_timeout_to_jiffies(), which needs to handle arguments larger
> than MAX_JIFFY_OFFSET on 32-bit architectures.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/gpu/drm/etnaviv/etnaviv_drv.c | 19 +++++++++----------
> drivers/gpu/drm/etnaviv/etnaviv_drv.h | 21 +++++++++------------
> drivers/gpu/drm/etnaviv/etnaviv_gem.c | 5 ++---
> drivers/gpu/drm/etnaviv/etnaviv_gem.h | 2 +-
> drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 4 ++--
> drivers/gpu/drm/etnaviv/etnaviv_gpu.h | 4 ++--
> 6 files changed, 25 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> index 1f9c01be40d7..1250c5e06329 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> @@ -282,16 +282,13 @@ static int etnaviv_ioctl_gem_new(struct drm_device *dev, void *data,
> args->flags, &args->handle);
> }
>
> -#define TS(t) ((struct timespec){ \
> - .tv_sec = (t).tv_sec, \
> - .tv_nsec = (t).tv_nsec \
> -})
> -
> static int etnaviv_ioctl_gem_cpu_prep(struct drm_device *dev, void *data,
> struct drm_file *file)
> {
> struct drm_etnaviv_gem_cpu_prep *args = data;
> struct drm_gem_object *obj;
> + ktime_t timeout = ktime_set(args->timeout.tv_sec,
> + args->timeout.tv_nsec);
> int ret;
>
> if (args->op & ~(ETNA_PREP_READ | ETNA_PREP_WRITE | ETNA_PREP_NOSYNC))
> @@ -301,7 +298,7 @@ static int etnaviv_ioctl_gem_cpu_prep(struct drm_device *dev, void *data,
> if (!obj)
> return -ENOENT;
>
> - ret = etnaviv_gem_cpu_prep(obj, args->op, &TS(args->timeout));
> + ret = etnaviv_gem_cpu_prep(obj, args->op, timeout);
>
> drm_gem_object_put_unlocked(obj);
>
> @@ -354,7 +351,8 @@ static int etnaviv_ioctl_wait_fence(struct drm_device *dev, void *data,
> {
> struct drm_etnaviv_wait_fence *args = data;
> struct etnaviv_drm_private *priv = dev->dev_private;
> - struct timespec *timeout = &TS(args->timeout);
> + ktime_t timeout = ktime_set(args->timeout.tv_sec,
> + args->timeout.tv_nsec);
> struct etnaviv_gpu *gpu;
>
> if (args->flags & ~(ETNA_WAIT_NONBLOCK))
> @@ -368,7 +366,7 @@ static int etnaviv_ioctl_wait_fence(struct drm_device *dev, void *data,
> return -ENXIO;
>
> if (args->flags & ETNA_WAIT_NONBLOCK)
> - timeout = NULL;
> + timeout = ktime_set(0, 0);

This is a change in behavior, as far as I can see. After this change
the called internal function is not able to differentiate between a
NONBLOCK call and a blocking call with 0 timeout. The difference being
that on a busy object the NONBLOCK call will return -EBUSY, while a
blocking call will return -ETIMEDOUT.

But then CLOCK_MONOTONIC starts at 0 and should not never wrap, right?
If that's the case then we should never encounter a genuine 0 timeout
and this change would be okay.

Regards,
Lucas
>
> return etnaviv_gpu_wait_fence_interruptible(gpu, args->fence,
> timeout);
> @@ -403,7 +401,8 @@ static int etnaviv_ioctl_gem_wait(struct drm_device *dev, void *data,
> {
> struct etnaviv_drm_private *priv = dev->dev_private;
> struct drm_etnaviv_gem_wait *args = data;
> - struct timespec *timeout = &TS(args->timeout);
> + ktime_t timeout = ktime_set(args->timeout.tv_sec,
> + args->timeout.tv_nsec);
> struct drm_gem_object *obj;
> struct etnaviv_gpu *gpu;
> int ret;
> @@ -423,7 +422,7 @@ static int etnaviv_ioctl_gem_wait(struct drm_device *dev, void *data,
> return -ENOENT;
>
> if (args->flags & ETNA_WAIT_NONBLOCK)
> - timeout = NULL;
> + timeout = ktime_set(0, 0);
>
> ret = etnaviv_gem_wait_bo(gpu, obj, timeout);
>
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.h b/drivers/gpu/drm/etnaviv/etnaviv_drv.h
> index 32cfa5a48d42..57a4e247bbcf 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.h
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.h
> @@ -60,8 +60,7 @@ struct drm_gem_object *etnaviv_gem_prime_import_sg_table(struct drm_device *dev,
> int etnaviv_gem_prime_pin(struct drm_gem_object *obj);
> void etnaviv_gem_prime_unpin(struct drm_gem_object *obj);
> void *etnaviv_gem_vmap(struct drm_gem_object *obj);
> -int etnaviv_gem_cpu_prep(struct drm_gem_object *obj, u32 op,
> - struct timespec *timeout);
> +int etnaviv_gem_cpu_prep(struct drm_gem_object *obj, u32 op, ktime_t timeout);
> int etnaviv_gem_cpu_fini(struct drm_gem_object *obj);
> void etnaviv_gem_free_object(struct drm_gem_object *obj);
> int etnaviv_gem_new_handle(struct drm_device *dev, struct drm_file *file,
> @@ -106,22 +105,20 @@ static inline size_t size_vstruct(size_t nelem, size_t elem_size, size_t base)
> * We need to calculate the timeout in terms of number of jiffies
> * between the specified timeout and the current CLOCK_MONOTONIC time.
> */
> -static inline unsigned long etnaviv_timeout_to_jiffies(
> - const struct timespec *timeout)
> +static inline unsigned long etnaviv_timeout_to_jiffies(ktime_t timeout)
> {
> - struct timespec64 ts, to;
> -
> - to = timespec_to_timespec64(*timeout);
> -
> - ktime_get_ts64(&ts);
> + s64 remain = ktime_to_ns(ktime_sub(timeout, ktime_get()));
>
> /* timeouts before "now" have already expired */
> - if (timespec64_compare(&to, &ts) <= 0)
> + if (remain < 0)
> return 0;
>
> - ts = timespec64_sub(to, ts);
> +#ifndef CONFIG_64BIT
> + if (remain > ((s64)MAX_JIFFY_OFFSET * NSEC_PER_SEC / HZ))
> + return MAX_JIFFY_OFFSET;
> +#endif
>
> - return timespec64_to_jiffies(&ts);
> + return nsecs_to_jiffies(remain);
> }
>
> #endif /* __ETNAVIV_DRV_H__ */
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> index cb1faaac380a..febe5196788e 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> @@ -372,8 +372,7 @@ static inline enum dma_data_direction etnaviv_op_to_dma_dir(u32 op)
> return DMA_BIDIRECTIONAL;
> }
>
> -int etnaviv_gem_cpu_prep(struct drm_gem_object *obj, u32 op,
> - struct timespec *timeout)
> +int etnaviv_gem_cpu_prep(struct drm_gem_object *obj, u32 op, ktime_t timeout)
> {
> struct etnaviv_gem_object *etnaviv_obj = to_etnaviv_bo(obj);
> struct drm_device *dev = obj->dev;
> @@ -431,7 +430,7 @@ int etnaviv_gem_cpu_fini(struct drm_gem_object *obj)
> }
>
> int etnaviv_gem_wait_bo(struct etnaviv_gpu *gpu, struct drm_gem_object *obj,
> - struct timespec *timeout)
> + ktime_t timeout)
> {
> struct etnaviv_gem_object *etnaviv_obj = to_etnaviv_bo(obj);
>
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.h b/drivers/gpu/drm/etnaviv/etnaviv_gem.h
> index d6270acce619..a3461a554a6c 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.h
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.h
> @@ -112,7 +112,7 @@ struct etnaviv_gem_submit {
> void etnaviv_submit_put(struct etnaviv_gem_submit * submit);
>
> int etnaviv_gem_wait_bo(struct etnaviv_gpu *gpu, struct drm_gem_object *obj,
> - struct timespec *timeout);
> + ktime_t timeout);
> int etnaviv_gem_new_private(struct drm_device *dev, size_t size, u32 flags,
> const struct etnaviv_gem_ops *ops, struct etnaviv_gem_object **res);
> void etnaviv_gem_obj_add(struct drm_device *dev, struct drm_gem_object *obj);
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> index d47d1a8e0219..e42b1c4d902c 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> @@ -1132,7 +1132,7 @@ static void event_free(struct etnaviv_gpu *gpu, unsigned int event)
> * Cmdstream submission/retirement:
> */
> int etnaviv_gpu_wait_fence_interruptible(struct etnaviv_gpu *gpu,
> - u32 id, struct timespec *timeout)
> + u32 id, ktime_t timeout)
> {
> struct dma_fence *fence;
> int ret;
> @@ -1179,7 +1179,7 @@ int etnaviv_gpu_wait_fence_interruptible(struct etnaviv_gpu *gpu,
> * that lock in this function while waiting.
> */
> int etnaviv_gpu_wait_obj_inactive(struct etnaviv_gpu *gpu,
> - struct etnaviv_gem_object *etnaviv_obj, struct timespec *timeout)
> + struct etnaviv_gem_object *etnaviv_obj, ktime_t timeout)
> {
> unsigned long remaining;
> long ret;
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> index 8f9bd4edc96a..6d352a435427 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
> @@ -169,9 +169,9 @@ int etnaviv_gpu_debugfs(struct etnaviv_gpu *gpu, struct seq_file *m);
> void etnaviv_gpu_recover_hang(struct etnaviv_gpu *gpu);
> void etnaviv_gpu_retire(struct etnaviv_gpu *gpu);
> int etnaviv_gpu_wait_fence_interruptible(struct etnaviv_gpu *gpu,
> - u32 fence, struct timespec *timeout);
> + u32 fence, ktime_t timeout);
> int etnaviv_gpu_wait_obj_inactive(struct etnaviv_gpu *gpu,
> - struct etnaviv_gem_object *etnaviv_obj, struct timespec *timeout);
> + struct etnaviv_gem_object *etnaviv_obj, ktime_t timeout);
> struct dma_fence *etnaviv_gpu_submit(struct etnaviv_gem_submit *submit);
> int etnaviv_gpu_pm_get_sync(struct etnaviv_gpu *gpu);
> void etnaviv_gpu_pm_put(struct etnaviv_gpu *gpu);