| Message ID | 20180823231634.GA17011@haneenDRM (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/vkms: Fix race condition around accessing frame number | expand |
On Fri, Aug 24, 2018 at 02:16:34AM +0300, Haneen Mohammed wrote: > crtc_state is accessed by both vblank_handle() and the ordered > work_struct handle vkms_crc_work_handle() to retrieve and or update > the frame number for computed CRC. > > Since work_struct can fail, add frame_end to account for missing frame > numbers. > > use atomic_t witth appropriate flags for synchronization between hrtimer > callback and ordered work_struct handle since spinlock can't be used > with work_struct handle and mutex can't be used with hrtimer callback. > > This patch passes the following subtests from igt kms_pipe_crc_basic test: > bad-source, read-crc-pipe-A, read-crc-pipe-A-frame-sequence, > nonblocking-crc-pipe-A, nonblocking-crc-pipe-A-frame-sequence > > Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com> So atomic_t is probably the greatest trap in the linux kernel. It sounds like the right thing, but in 99% of all case you want to use it it isn't. The trouble is that atomic_t is _very_ unordered, the only thing it guarantees is that atomic_t transactions to the _same_ variable are consistent. But anything else can be reordered at will. This is very confusing since the new C++ atomic standards has fully ordered atomics as the default, and you expressedly need to ask for the weakly ordered ones. In linux you need to sprinkle epic amounts of smb_barrier* and similar things around them to make atomic_t behave like a "normal" C++ atomic type. tldr; atomic_t is good for special refcounting needs, when the normal refcount_t doesn't cut it. Not much else. What usually should be done: - Use normal u64 (to match the vblank counter size) instead of atomic_t here. - Make sure all access is protect by an appropriate spinlock. > --- > drivers/gpu/drm/vkms/vkms_crc.c | 33 ++++++++++++++++++++++++++++++-- > drivers/gpu/drm/vkms/vkms_crtc.c | 13 +++++++++++-- > drivers/gpu/drm/vkms/vkms_drv.h | 6 ++++-- > 3 files changed, 46 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/vkms/vkms_crc.c b/drivers/gpu/drm/vkms/vkms_crc.c > index ed47d67cecd6..4a1ba5b7886a 100644 > --- a/drivers/gpu/drm/vkms/vkms_crc.c > +++ b/drivers/gpu/drm/vkms/vkms_crc.c > @@ -34,6 +34,15 @@ static uint32_t _vkms_get_crc(struct vkms_crc_data *crc_data) > return crc; > } > > +/** > + * vkms_crc_work_handle - ordered work_struct to compute CRC > + * > + * @work: work_struct > + * > + * Work handler for computing CRCs. work_struct scheduled in > + * an ordered workqueue that's periodically scheduled to run by > + * _vblank_handle() and flushed at vkms_atomic_crtc_destroy_state(). > + */ > void vkms_crc_work_handle(struct work_struct *work) > { > struct vkms_crtc_state *crtc_state = container_of(work, > @@ -45,8 +54,18 @@ void vkms_crc_work_handle(struct work_struct *work) > output); > struct vkms_crc_data *primary_crc = NULL; > struct drm_plane *plane; > - > u32 crc32 = 0; > + u32 frame_start, frame_end; > + > + frame_start = atomic_read(&crtc_state->frame_start); > + frame_end = atomic_read(&crtc_state->frame_end); > + /* _vblank_handle() hasn't updated frame_start yet */ > + if (!frame_start) { I think if we go with u64 we can ignore the issues for wrap-arround, since that will simply never happen. But a comment would be good. Aside from the atomic_t issue I think this looks good. -Daniel > + return; > + } else if (frame_start == frame_end) { > + atomic_set(&crtc_state->frame_start, 0); > + return; > + } > > drm_for_each_plane(plane, &vdev->drm) { > struct vkms_plane_state *vplane_state; > @@ -67,7 +86,17 @@ void vkms_crc_work_handle(struct work_struct *work) > if (primary_crc) > crc32 = _vkms_get_crc(primary_crc); > > - drm_crtc_add_crc_entry(crtc, true, crtc_state->n_frame, &crc32); > + frame_end = drm_crtc_accurate_vblank_count(crtc); > + > + /* queue_work can fail to schedule crc_work; add crc for > + * missing frames > + */ > + while (frame_start <= frame_end) > + drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32); > + > + /* to avoid using the same value again */ > + atomic_set(&crtc_state->frame_end, frame_end); > + atomic_set(&crtc_state->frame_start, 0); > } > > static int vkms_crc_parse_source(const char *src_name, bool *enabled) > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c > index 9d0b1a325a78..a170677acd46 100644 > --- a/drivers/gpu/drm/vkms/vkms_crtc.c > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c > @@ -22,8 +22,17 @@ static void _vblank_handle(struct vkms_output *output) > DRM_ERROR("vkms failure on handling vblank"); > > if (state && output->crc_enabled) { > - state->n_frame = drm_crtc_accurate_vblank_count(crtc); > - queue_work(output->crc_workq, &state->crc_work); > + u32 frame = drm_crtc_accurate_vblank_count(crtc); > + > + /* update frame_start only if a queued vkms_crc_work_handle has > + * read the data > + */ > + if (!atomic_read(&state->frame_start)) > + atomic_set(&state->frame_start, frame); > + > + ret = queue_work(output->crc_workq, &state->crc_work); > + if (!ret) > + DRM_WARN("failed to queue vkms_crc_work_handle"); > } > > spin_unlock(&output->lock); > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h > index 2017a2ccc43d..4a3956a0549e 100644 > --- a/drivers/gpu/drm/vkms/vkms_drv.h > +++ b/drivers/gpu/drm/vkms/vkms_drv.h > @@ -39,12 +39,14 @@ struct vkms_plane_state { > * vkms_crtc_state - Driver specific CRTC state > * @base: base CRTC state > * @crc_work: work struct to compute and add CRC entries > - * @n_frame: frame number for computed CRC > + * @n_frame_start: start frame number for computed CRC > + * @n_frame_end: end frame number for computed CRC > */ > struct vkms_crtc_state { > struct drm_crtc_state base; > struct work_struct crc_work; > - unsigned int n_frame; > + atomic_t frame_start; > + atomic_t frame_end; > }; > > struct vkms_output { > -- > 2.17.1 >
On Fri, Aug 31, 2018 at 10:41:40AM +0200, Daniel Vetter wrote: > On Fri, Aug 24, 2018 at 02:16:34AM +0300, Haneen Mohammed wrote: > > crtc_state is accessed by both vblank_handle() and the ordered > > work_struct handle vkms_crc_work_handle() to retrieve and or update > > the frame number for computed CRC. > > > > Since work_struct can fail, add frame_end to account for missing frame > > numbers. > > > > use atomic_t witth appropriate flags for synchronization between hrtimer > > callback and ordered work_struct handle since spinlock can't be used > > with work_struct handle and mutex can't be used with hrtimer callback. > > > > This patch passes the following subtests from igt kms_pipe_crc_basic test: > > bad-source, read-crc-pipe-A, read-crc-pipe-A-frame-sequence, > > nonblocking-crc-pipe-A, nonblocking-crc-pipe-A-frame-sequence > > > > Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com> > > So atomic_t is probably the greatest trap in the linux kernel. It sounds > like the right thing, but in 99% of all case you want to use it it isn't. > The trouble is that atomic_t is _very_ unordered, the only thing it > guarantees is that atomic_t transactions to the _same_ variable are > consistent. But anything else can be reordered at will. > > This is very confusing since the new C++ atomic standards has fully > ordered atomics as the default, and you expressedly need to ask for the > weakly ordered ones. In linux you need to sprinkle epic amounts of > smb_barrier* and similar things around them to make atomic_t behave like a > "normal" C++ atomic type. > > tldr; atomic_t is good for special refcounting needs, when the normal > refcount_t doesn't cut it. Not much else. > > What usually should be done: > - Use normal u64 (to match the vblank counter size) instead of atomic_t > here. > - Make sure all access is protect by an appropriate spinlock. > I see, thanks for the explanation! hm would the patch be fine if I just switch atomic_t to u64 without using spinlock? since that won't be possible with the work_struct. Thanks, Haneen > > --- > > drivers/gpu/drm/vkms/vkms_crc.c | 33 ++++++++++++++++++++++++++++++-- > > drivers/gpu/drm/vkms/vkms_crtc.c | 13 +++++++++++-- > > drivers/gpu/drm/vkms/vkms_drv.h | 6 ++++-- > > 3 files changed, 46 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/gpu/drm/vkms/vkms_crc.c b/drivers/gpu/drm/vkms/vkms_crc.c > > index ed47d67cecd6..4a1ba5b7886a 100644 > > --- a/drivers/gpu/drm/vkms/vkms_crc.c > > +++ b/drivers/gpu/drm/vkms/vkms_crc.c > > @@ -34,6 +34,15 @@ static uint32_t _vkms_get_crc(struct vkms_crc_data *crc_data) > > return crc; > > } > > > > +/** > > + * vkms_crc_work_handle - ordered work_struct to compute CRC > > + * > > + * @work: work_struct > > + * > > + * Work handler for computing CRCs. work_struct scheduled in > > + * an ordered workqueue that's periodically scheduled to run by > > + * _vblank_handle() and flushed at vkms_atomic_crtc_destroy_state(). > > + */ > > void vkms_crc_work_handle(struct work_struct *work) > > { > > struct vkms_crtc_state *crtc_state = container_of(work, > > @@ -45,8 +54,18 @@ void vkms_crc_work_handle(struct work_struct *work) > > output); > > struct vkms_crc_data *primary_crc = NULL; > > struct drm_plane *plane; > > - > > u32 crc32 = 0; > > + u32 frame_start, frame_end; > > + > > + frame_start = atomic_read(&crtc_state->frame_start); > > + frame_end = atomic_read(&crtc_state->frame_end); > > + /* _vblank_handle() hasn't updated frame_start yet */ > > + if (!frame_start) { > > I think if we go with u64 we can ignore the issues for wrap-arround, since > that will simply never happen. But a comment would be good. > > Aside from the atomic_t issue I think this looks good. > -Daniel > > > + return; > > + } else if (frame_start == frame_end) { > > + atomic_set(&crtc_state->frame_start, 0); > > + return; > > + } > > > > drm_for_each_plane(plane, &vdev->drm) { > > struct vkms_plane_state *vplane_state; > > @@ -67,7 +86,17 @@ void vkms_crc_work_handle(struct work_struct *work) > > if (primary_crc) > > crc32 = _vkms_get_crc(primary_crc); > > > > - drm_crtc_add_crc_entry(crtc, true, crtc_state->n_frame, &crc32); > > + frame_end = drm_crtc_accurate_vblank_count(crtc); > > + > > + /* queue_work can fail to schedule crc_work; add crc for > > + * missing frames > > + */ > > + while (frame_start <= frame_end) > > + drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32); > > + > > + /* to avoid using the same value again */ > > + atomic_set(&crtc_state->frame_end, frame_end); > > + atomic_set(&crtc_state->frame_start, 0); > > } > > > > static int vkms_crc_parse_source(const char *src_name, bool *enabled) > > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c > > index 9d0b1a325a78..a170677acd46 100644 > > --- a/drivers/gpu/drm/vkms/vkms_crtc.c > > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c > > @@ -22,8 +22,17 @@ static void _vblank_handle(struct vkms_output *output) > > DRM_ERROR("vkms failure on handling vblank"); > > > > if (state && output->crc_enabled) { > > - state->n_frame = drm_crtc_accurate_vblank_count(crtc); > > - queue_work(output->crc_workq, &state->crc_work); > > + u32 frame = drm_crtc_accurate_vblank_count(crtc); > > + > > + /* update frame_start only if a queued vkms_crc_work_handle has > > + * read the data > > + */ > > + if (!atomic_read(&state->frame_start)) > > + atomic_set(&state->frame_start, frame); > > + > > + ret = queue_work(output->crc_workq, &state->crc_work); > > + if (!ret) > > + DRM_WARN("failed to queue vkms_crc_work_handle"); > > } > > > > spin_unlock(&output->lock); > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h > > index 2017a2ccc43d..4a3956a0549e 100644 > > --- a/drivers/gpu/drm/vkms/vkms_drv.h > > +++ b/drivers/gpu/drm/vkms/vkms_drv.h > > @@ -39,12 +39,14 @@ struct vkms_plane_state { > > * vkms_crtc_state - Driver specific CRTC state > > * @base: base CRTC state > > * @crc_work: work struct to compute and add CRC entries > > - * @n_frame: frame number for computed CRC > > + * @n_frame_start: start frame number for computed CRC > > + * @n_frame_end: end frame number for computed CRC > > */ > > struct vkms_crtc_state { > > struct drm_crtc_state base; > > struct work_struct crc_work; > > - unsigned int n_frame; > > + atomic_t frame_start; > > + atomic_t frame_end; > > }; > > > > struct vkms_output { > > -- > > 2.17.1 > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
On Sat, Sep 01, 2018 at 08:53:52PM +0300, Haneen Mohammed wrote: > On Fri, Aug 31, 2018 at 10:41:40AM +0200, Daniel Vetter wrote: > > On Fri, Aug 24, 2018 at 02:16:34AM +0300, Haneen Mohammed wrote: > > > crtc_state is accessed by both vblank_handle() and the ordered > > > work_struct handle vkms_crc_work_handle() to retrieve and or update > > > the frame number for computed CRC. > > > > > > Since work_struct can fail, add frame_end to account for missing frame > > > numbers. > > > > > > use atomic_t witth appropriate flags for synchronization between hrtimer > > > callback and ordered work_struct handle since spinlock can't be used > > > with work_struct handle and mutex can't be used with hrtimer callback. > > > > > > This patch passes the following subtests from igt kms_pipe_crc_basic test: > > > bad-source, read-crc-pipe-A, read-crc-pipe-A-frame-sequence, > > > nonblocking-crc-pipe-A, nonblocking-crc-pipe-A-frame-sequence > > > > > > Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com> > > > > So atomic_t is probably the greatest trap in the linux kernel. It sounds > > like the right thing, but in 99% of all case you want to use it it isn't. > > The trouble is that atomic_t is _very_ unordered, the only thing it > > guarantees is that atomic_t transactions to the _same_ variable are > > consistent. But anything else can be reordered at will. > > > > This is very confusing since the new C++ atomic standards has fully > > ordered atomics as the default, and you expressedly need to ask for the > > weakly ordered ones. In linux you need to sprinkle epic amounts of > > smb_barrier* and similar things around them to make atomic_t behave like a > > "normal" C++ atomic type. > > > > tldr; atomic_t is good for special refcounting needs, when the normal > > refcount_t doesn't cut it. Not much else. > > > > What usually should be done: > > - Use normal u64 (to match the vblank counter size) instead of atomic_t > > here. > > - Make sure all access is protect by an appropriate spinlock. > > > > I see, thanks for the explanation! > > hm would the patch be fine if I just switch atomic_t to u64 without > using spinlock? since that won't be possible with the work_struct. Why can't you use the spin_lock from the worker? You need the spin_lock_irq variant, plus a bit of pointer chasing, but should be doable ... Cheers, Daniel > > Thanks, > Haneen > > > > --- > > > drivers/gpu/drm/vkms/vkms_crc.c | 33 ++++++++++++++++++++++++++++++-- > > > drivers/gpu/drm/vkms/vkms_crtc.c | 13 +++++++++++-- > > > drivers/gpu/drm/vkms/vkms_drv.h | 6 ++++-- > > > 3 files changed, 46 insertions(+), 6 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/vkms/vkms_crc.c b/drivers/gpu/drm/vkms/vkms_crc.c > > > index ed47d67cecd6..4a1ba5b7886a 100644 > > > --- a/drivers/gpu/drm/vkms/vkms_crc.c > > > +++ b/drivers/gpu/drm/vkms/vkms_crc.c > > > @@ -34,6 +34,15 @@ static uint32_t _vkms_get_crc(struct vkms_crc_data *crc_data) > > > return crc; > > > } > > > > > > +/** > > > + * vkms_crc_work_handle - ordered work_struct to compute CRC > > > + * > > > + * @work: work_struct > > > + * > > > + * Work handler for computing CRCs. work_struct scheduled in > > > + * an ordered workqueue that's periodically scheduled to run by > > > + * _vblank_handle() and flushed at vkms_atomic_crtc_destroy_state(). > > > + */ > > > void vkms_crc_work_handle(struct work_struct *work) > > > { > > > struct vkms_crtc_state *crtc_state = container_of(work, > > > @@ -45,8 +54,18 @@ void vkms_crc_work_handle(struct work_struct *work) > > > output); > > > struct vkms_crc_data *primary_crc = NULL; > > > struct drm_plane *plane; > > > - > > > u32 crc32 = 0; > > > + u32 frame_start, frame_end; > > > + > > > + frame_start = atomic_read(&crtc_state->frame_start); > > > + frame_end = atomic_read(&crtc_state->frame_end); > > > + /* _vblank_handle() hasn't updated frame_start yet */ > > > + if (!frame_start) { > > > > I think if we go with u64 we can ignore the issues for wrap-arround, since > > that will simply never happen. But a comment would be good. > > > > Aside from the atomic_t issue I think this looks good. > > -Daniel > > > > > + return; > > > + } else if (frame_start == frame_end) { > > > + atomic_set(&crtc_state->frame_start, 0); > > > + return; > > > + } > > > > > > drm_for_each_plane(plane, &vdev->drm) { > > > struct vkms_plane_state *vplane_state; > > > @@ -67,7 +86,17 @@ void vkms_crc_work_handle(struct work_struct *work) > > > if (primary_crc) > > > crc32 = _vkms_get_crc(primary_crc); > > > > > > - drm_crtc_add_crc_entry(crtc, true, crtc_state->n_frame, &crc32); > > > + frame_end = drm_crtc_accurate_vblank_count(crtc); > > > + > > > + /* queue_work can fail to schedule crc_work; add crc for > > > + * missing frames > > > + */ > > > + while (frame_start <= frame_end) > > > + drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32); > > > + > > > + /* to avoid using the same value again */ > > > + atomic_set(&crtc_state->frame_end, frame_end); > > > + atomic_set(&crtc_state->frame_start, 0); > > > } > > > > > > static int vkms_crc_parse_source(const char *src_name, bool *enabled) > > > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c > > > index 9d0b1a325a78..a170677acd46 100644 > > > --- a/drivers/gpu/drm/vkms/vkms_crtc.c > > > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c > > > @@ -22,8 +22,17 @@ static void _vblank_handle(struct vkms_output *output) > > > DRM_ERROR("vkms failure on handling vblank"); > > > > > > if (state && output->crc_enabled) { > > > - state->n_frame = drm_crtc_accurate_vblank_count(crtc); > > > - queue_work(output->crc_workq, &state->crc_work); > > > + u32 frame = drm_crtc_accurate_vblank_count(crtc); > > > + > > > + /* update frame_start only if a queued vkms_crc_work_handle has > > > + * read the data > > > + */ > > > + if (!atomic_read(&state->frame_start)) > > > + atomic_set(&state->frame_start, frame); > > > + > > > + ret = queue_work(output->crc_workq, &state->crc_work); > > > + if (!ret) > > > + DRM_WARN("failed to queue vkms_crc_work_handle"); > > > } > > > > > > spin_unlock(&output->lock); > > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h > > > index 2017a2ccc43d..4a3956a0549e 100644 > > > --- a/drivers/gpu/drm/vkms/vkms_drv.h > > > +++ b/drivers/gpu/drm/vkms/vkms_drv.h > > > @@ -39,12 +39,14 @@ struct vkms_plane_state { > > > * vkms_crtc_state - Driver specific CRTC state > > > * @base: base CRTC state > > > * @crc_work: work struct to compute and add CRC entries > > > - * @n_frame: frame number for computed CRC > > > + * @n_frame_start: start frame number for computed CRC > > > + * @n_frame_end: end frame number for computed CRC > > > */ > > > struct vkms_crtc_state { > > > struct drm_crtc_state base; > > > struct work_struct crc_work; > > > - unsigned int n_frame; > > > + atomic_t frame_start; > > > + atomic_t frame_end; > > > }; > > > > > > struct vkms_output { > > > -- > > > 2.17.1 > > > > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch
diff --git a/drivers/gpu/drm/vkms/vkms_crc.c b/drivers/gpu/drm/vkms/vkms_crc.c index ed47d67cecd6..4a1ba5b7886a 100644 --- a/drivers/gpu/drm/vkms/vkms_crc.c +++ b/drivers/gpu/drm/vkms/vkms_crc.c @@ -34,6 +34,15 @@ static uint32_t _vkms_get_crc(struct vkms_crc_data *crc_data) return crc; } +/** + * vkms_crc_work_handle - ordered work_struct to compute CRC + * + * @work: work_struct + * + * Work handler for computing CRCs. work_struct scheduled in + * an ordered workqueue that's periodically scheduled to run by + * _vblank_handle() and flushed at vkms_atomic_crtc_destroy_state(). + */ void vkms_crc_work_handle(struct work_struct *work) { struct vkms_crtc_state *crtc_state = container_of(work, @@ -45,8 +54,18 @@ void vkms_crc_work_handle(struct work_struct *work) output); struct vkms_crc_data *primary_crc = NULL; struct drm_plane *plane; - u32 crc32 = 0; + u32 frame_start, frame_end; + + frame_start = atomic_read(&crtc_state->frame_start); + frame_end = atomic_read(&crtc_state->frame_end); + /* _vblank_handle() hasn't updated frame_start yet */ + if (!frame_start) { + return; + } else if (frame_start == frame_end) { + atomic_set(&crtc_state->frame_start, 0); + return; + } drm_for_each_plane(plane, &vdev->drm) { struct vkms_plane_state *vplane_state; @@ -67,7 +86,17 @@ void vkms_crc_work_handle(struct work_struct *work) if (primary_crc) crc32 = _vkms_get_crc(primary_crc); - drm_crtc_add_crc_entry(crtc, true, crtc_state->n_frame, &crc32); + frame_end = drm_crtc_accurate_vblank_count(crtc); + + /* queue_work can fail to schedule crc_work; add crc for + * missing frames + */ + while (frame_start <= frame_end) + drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32); + + /* to avoid using the same value again */ + atomic_set(&crtc_state->frame_end, frame_end); + atomic_set(&crtc_state->frame_start, 0); } static int vkms_crc_parse_source(const char *src_name, bool *enabled) diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c index 9d0b1a325a78..a170677acd46 100644 --- a/drivers/gpu/drm/vkms/vkms_crtc.c +++ b/drivers/gpu/drm/vkms/vkms_crtc.c @@ -22,8 +22,17 @@ static void _vblank_handle(struct vkms_output *output) DRM_ERROR("vkms failure on handling vblank"); if (state && output->crc_enabled) { - state->n_frame = drm_crtc_accurate_vblank_count(crtc); - queue_work(output->crc_workq, &state->crc_work); + u32 frame = drm_crtc_accurate_vblank_count(crtc); + + /* update frame_start only if a queued vkms_crc_work_handle has + * read the data + */ + if (!atomic_read(&state->frame_start)) + atomic_set(&state->frame_start, frame); + + ret = queue_work(output->crc_workq, &state->crc_work); + if (!ret) + DRM_WARN("failed to queue vkms_crc_work_handle"); } spin_unlock(&output->lock); diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h index 2017a2ccc43d..4a3956a0549e 100644 --- a/drivers/gpu/drm/vkms/vkms_drv.h +++ b/drivers/gpu/drm/vkms/vkms_drv.h @@ -39,12 +39,14 @@ struct vkms_plane_state { * vkms_crtc_state - Driver specific CRTC state * @base: base CRTC state * @crc_work: work struct to compute and add CRC entries - * @n_frame: frame number for computed CRC + * @n_frame_start: start frame number for computed CRC + * @n_frame_end: end frame number for computed CRC */ struct vkms_crtc_state { struct drm_crtc_state base; struct work_struct crc_work; - unsigned int n_frame; + atomic_t frame_start; + atomic_t frame_end; }; struct vkms_output {
crtc_state is accessed by both vblank_handle() and the ordered work_struct handle vkms_crc_work_handle() to retrieve and or update the frame number for computed CRC. Since work_struct can fail, add frame_end to account for missing frame numbers. use atomic_t witth appropriate flags for synchronization between hrtimer callback and ordered work_struct handle since spinlock can't be used with work_struct handle and mutex can't be used with hrtimer callback. This patch passes the following subtests from igt kms_pipe_crc_basic test: bad-source, read-crc-pipe-A, read-crc-pipe-A-frame-sequence, nonblocking-crc-pipe-A, nonblocking-crc-pipe-A-frame-sequence Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com> --- drivers/gpu/drm/vkms/vkms_crc.c | 33 ++++++++++++++++++++++++++++++-- drivers/gpu/drm/vkms/vkms_crtc.c | 13 +++++++++++-- drivers/gpu/drm/vkms/vkms_drv.h | 6 ++++-- 3 files changed, 46 insertions(+), 6 deletions(-)