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SubjectRe: [PATCH 1/2] habanalabs: Replace dma-fence mechanism with completions
On Thu, Jul 30, 2020 at 3:13 PM Oded Gabbay <oded.gabbay@gmail.com> wrote:
>
> From: Ofir Bitton <obitton@habana.ai>
>
> habanalabs driver uses dma-fence mechanism for synchronization.
> dma-fence mechanism was designed solely for GPUs, hence we purpose
> a simpler mechanism based on completions to replace current
> dma-fence objects.
>
> Signed-off-by: Ofir Bitton <obitton@habana.ai>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
> Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

Are you sure you need kfree_rcu for hl_fence? That was a requirement
from dma_fence, because we do _tons_ of rcu protected lockups of those
in gpu drivers (e.g. struct dma_resv). But a quick git grep says
habanalabs driver doesn't use any rcu, so a simple kfree() should be
fine, and allows you to further simplify hl_fence. With that change
this is:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Cheers, Daniel

> ---
> .../habanalabs/common/command_submission.c | 93 +++++++++----------
> drivers/misc/habanalabs/common/context.c | 13 +--
> drivers/misc/habanalabs/common/habanalabs.h | 32 +++++--
> drivers/misc/habanalabs/common/hw_queue.c | 2 +-
> 4 files changed, 78 insertions(+), 62 deletions(-)
>
> diff --git a/drivers/misc/habanalabs/common/command_submission.c b/drivers/misc/habanalabs/common/command_submission.c
> index b9840e368eb5..d19ac641b171 100644
> --- a/drivers/misc/habanalabs/common/command_submission.c
> +++ b/drivers/misc/habanalabs/common/command_submission.c
> @@ -38,26 +38,10 @@ void hl_sob_reset_error(struct kref *ref)
> hw_sob->q_idx, hw_sob->sob_id);
> }
>
> -static const char *hl_fence_get_driver_name(struct dma_fence *fence)
> -{
> - return "HabanaLabs";
> -}
> -
> -static const char *hl_fence_get_timeline_name(struct dma_fence *fence)
> -{
> - struct hl_cs_compl *hl_cs_compl =
> - container_of(fence, struct hl_cs_compl, base_fence);
> -
> - return dev_name(hl_cs_compl->hdev->dev);
> -}
> -
> -static bool hl_fence_enable_signaling(struct dma_fence *fence)
> -{
> - return true;
> -}
> -
> -static void hl_fence_release(struct dma_fence *fence)
> +void hl_fence_release(struct kref *kref)
> {
> + struct hl_fence *fence =
> + container_of(kref, struct hl_fence, refcount);
> struct hl_cs_compl *hl_cs_cmpl =
> container_of(fence, struct hl_cs_compl, base_fence);
> struct hl_device *hdev = hl_cs_cmpl->hdev;
> @@ -102,12 +86,24 @@ static void hl_fence_release(struct dma_fence *fence)
> kfree_rcu(hl_cs_cmpl, base_fence.rcu);
> }
>
> -static const struct dma_fence_ops hl_fence_ops = {
> - .get_driver_name = hl_fence_get_driver_name,
> - .get_timeline_name = hl_fence_get_timeline_name,
> - .enable_signaling = hl_fence_enable_signaling,
> - .release = hl_fence_release
> -};
> +void hl_fence_put(struct hl_fence *fence)
> +{
> + if (fence)
> + kref_put(&fence->refcount, hl_fence_release);
> +}
> +
> +void hl_fence_get(struct hl_fence *fence)
> +{
> + if (fence)
> + kref_get(&fence->refcount);
> +}
> +
> +void hl_fence_init(struct hl_fence *fence)
> +{
> + kref_init(&fence->refcount);
> + fence->error = 0;
> + init_completion(&fence->completion);
> +}
>
> static void cs_get(struct hl_cs *cs)
> {
> @@ -336,7 +332,7 @@ static void cs_do_release(struct kref *ref)
> * In case the wait for signal CS was submitted, the put occurs
> * in init_signal_wait_cs() right before hanging on the PQ.
> */
> - dma_fence_put(cs->signal_fence);
> + hl_fence_put(cs->signal_fence);
> }
>
> /*
> @@ -348,19 +344,18 @@ static void cs_do_release(struct kref *ref)
> hl_ctx_put(cs->ctx);
>
> /* We need to mark an error for not submitted because in that case
> - * the dma fence release flow is different. Mainly, we don't need
> + * the hl fence release flow is different. Mainly, we don't need
> * to handle hw_sob for signal/wait
> */
> if (cs->timedout)
> - dma_fence_set_error(cs->fence, -ETIMEDOUT);
> + cs->fence->error = -ETIMEDOUT;
> else if (cs->aborted)
> - dma_fence_set_error(cs->fence, -EIO);
> + cs->fence->error = -EIO;
> else if (!cs->submitted)
> - dma_fence_set_error(cs->fence, -EBUSY);
> -
> - dma_fence_signal(cs->fence);
> - dma_fence_put(cs->fence);
> + cs->fence->error = -EBUSY;
>
> + complete_all(&cs->fence->completion);
> + hl_fence_put(cs->fence);
> cs_counters_aggregate(hdev, cs->ctx);
>
> kfree(cs->jobs_in_queue_cnt);
> @@ -401,7 +396,7 @@ static int allocate_cs(struct hl_device *hdev, struct hl_ctx *ctx,
> enum hl_cs_type cs_type, struct hl_cs **cs_new)
> {
> struct hl_cs_compl *cs_cmpl;
> - struct dma_fence *other = NULL;
> + struct hl_fence *other = NULL;
> struct hl_cs *cs;
> int rc;
>
> @@ -434,7 +429,8 @@ static int allocate_cs(struct hl_device *hdev, struct hl_ctx *ctx,
> cs_cmpl->cs_seq = ctx->cs_sequence;
> other = ctx->cs_pending[cs_cmpl->cs_seq &
> (hdev->asic_prop.max_pending_cs - 1)];
> - if ((other) && (!dma_fence_is_signaled(other))) {
> +
> + if (other && !completion_done(&other->completion)) {
> dev_dbg(hdev->dev,
> "Rejecting CS because of too many in-flights CS\n");
> rc = -EAGAIN;
> @@ -448,8 +444,8 @@ static int allocate_cs(struct hl_device *hdev, struct hl_ctx *ctx,
> goto free_fence;
> }
>
> - dma_fence_init(&cs_cmpl->base_fence, &hl_fence_ops, &cs_cmpl->lock,
> - ctx->asid, ctx->cs_sequence);
> + /* init hl_fence */
> + hl_fence_init(&cs_cmpl->base_fence);
>
> cs->sequence = cs_cmpl->cs_seq;
>
> @@ -458,9 +454,9 @@ static int allocate_cs(struct hl_device *hdev, struct hl_ctx *ctx,
> &cs_cmpl->base_fence;
> ctx->cs_sequence++;
>
> - dma_fence_get(&cs_cmpl->base_fence);
> + hl_fence_get(&cs_cmpl->base_fence);
>
> - dma_fence_put(other);
> + hl_fence_put(other);
>
> spin_unlock(&ctx->cs_lock);
>
> @@ -773,7 +769,7 @@ static int cs_ioctl_signal_wait(struct hl_fpriv *hpriv, enum hl_cs_type cs_type,
> struct hl_ctx *ctx = hpriv->ctx;
> struct hl_cs_chunk *cs_chunk_array, *chunk;
> struct hw_queue_properties *hw_queue_prop;
> - struct dma_fence *sig_fence = NULL;
> + struct hl_fence *sig_fence = NULL;
> struct hl_cs_job *job;
> struct hl_cs *cs;
> struct hl_cb *cb;
> @@ -875,14 +871,14 @@ static int cs_ioctl_signal_wait(struct hl_fpriv *hpriv, enum hl_cs_type cs_type,
> dev_err(hdev->dev,
> "CS seq 0x%llx is not of a signal CS\n",
> signal_seq);
> - dma_fence_put(sig_fence);
> + hl_fence_put(sig_fence);
> rc = -EINVAL;
> goto free_signal_seq_array;
> }
>
> - if (dma_fence_is_signaled(sig_fence)) {
> + if (completion_done(&sig_fence->completion)) {
> /* signal CS already finished */
> - dma_fence_put(sig_fence);
> + hl_fence_put(sig_fence);
> rc = 0;
> goto free_signal_seq_array;
> }
> @@ -894,7 +890,7 @@ static int cs_ioctl_signal_wait(struct hl_fpriv *hpriv, enum hl_cs_type cs_type,
> rc = allocate_cs(hdev, ctx, cs_type, &cs);
> if (rc) {
> if (cs_type == CS_TYPE_WAIT)
> - dma_fence_put(sig_fence);
> + hl_fence_put(sig_fence);
> hl_ctx_put(ctx);
> goto free_signal_seq_array;
> }
> @@ -1154,7 +1150,7 @@ int hl_cs_ioctl(struct hl_fpriv *hpriv, void *data)
> static long _hl_cs_wait_ioctl(struct hl_device *hdev,
> struct hl_ctx *ctx, u64 timeout_us, u64 seq)
> {
> - struct dma_fence *fence;
> + struct hl_fence *fence;
> unsigned long timeout;
> long rc;
>
> @@ -1173,12 +1169,15 @@ static long _hl_cs_wait_ioctl(struct hl_device *hdev,
> "Can't wait on CS %llu because current CS is at seq %llu\n",
> seq, ctx->cs_sequence);
> } else if (fence) {
> - rc = dma_fence_wait_timeout(fence, true, timeout);
> + rc = wait_for_completion_interruptible_timeout(
> + &fence->completion, timeout);
> +
> if (fence->error == -ETIMEDOUT)
> rc = -ETIMEDOUT;
> else if (fence->error == -EIO)
> rc = -EIO;
> - dma_fence_put(fence);
> +
> + hl_fence_put(fence);
> } else {
> dev_dbg(hdev->dev,
> "Can't wait on seq %llu because current CS is at seq %llu (Fence is gone)\n",
> diff --git a/drivers/misc/habanalabs/common/context.c b/drivers/misc/habanalabs/common/context.c
> index 3e375958e73b..b168a9fce817 100644
> --- a/drivers/misc/habanalabs/common/context.c
> +++ b/drivers/misc/habanalabs/common/context.c
> @@ -23,7 +23,7 @@ static void hl_ctx_fini(struct hl_ctx *ctx)
> */
>
> for (i = 0 ; i < hdev->asic_prop.max_pending_cs ; i++)
> - dma_fence_put(ctx->cs_pending[i]);
> + hl_fence_put(ctx->cs_pending[i]);
>
> kfree(ctx->cs_pending);
>
> @@ -128,7 +128,7 @@ int hl_ctx_init(struct hl_device *hdev, struct hl_ctx *ctx, bool is_kernel_ctx)
> atomic_set(&ctx->thread_ctx_switch_token, 1);
> ctx->thread_ctx_switch_wait_token = 0;
> ctx->cs_pending = kcalloc(hdev->asic_prop.max_pending_cs,
> - sizeof(struct dma_fence *),
> + sizeof(struct hl_fence *),
> GFP_KERNEL);
> if (!ctx->cs_pending)
> return -ENOMEM;
> @@ -184,10 +184,10 @@ int hl_ctx_put(struct hl_ctx *ctx)
> return kref_put(&ctx->refcount, hl_ctx_do_release);
> }
>
> -struct dma_fence *hl_ctx_get_fence(struct hl_ctx *ctx, u64 seq)
> +struct hl_fence *hl_ctx_get_fence(struct hl_ctx *ctx, u64 seq)
> {
> struct asic_fixed_properties *asic_prop = &ctx->hdev->asic_prop;
> - struct dma_fence *fence;
> + struct hl_fence *fence;
>
> spin_lock(&ctx->cs_lock);
>
> @@ -201,8 +201,9 @@ struct dma_fence *hl_ctx_get_fence(struct hl_ctx *ctx, u64 seq)
> return NULL;
> }
>
> - fence = dma_fence_get(
> - ctx->cs_pending[seq & (asic_prop->max_pending_cs - 1)]);
> + fence = ctx->cs_pending[seq & (asic_prop->max_pending_cs - 1)];
> + hl_fence_get(fence);
> +
> spin_unlock(&ctx->cs_lock);
>
> return fence;
> diff --git a/drivers/misc/habanalabs/common/habanalabs.h b/drivers/misc/habanalabs/common/habanalabs.h
> index 018d9d67e8e6..30a399337675 100644
> --- a/drivers/misc/habanalabs/common/habanalabs.h
> +++ b/drivers/misc/habanalabs/common/habanalabs.h
> @@ -15,7 +15,6 @@
> #include <linux/cdev.h>
> #include <linux/iopoll.h>
> #include <linux/irqreturn.h>
> -#include <linux/dma-fence.h>
> #include <linux/dma-direction.h>
> #include <linux/scatterlist.h>
> #include <linux/hashtable.h>
> @@ -342,9 +341,24 @@ struct asic_fixed_properties {
> u8 completion_queues_count;
> };
>
> +/**
> + * struct hl_fence - software synchronization primitive
> + * @completion: fence is implemented using completion
> + * @refcount: refcount for this fence
> + * @rcu: used for releasing fence with kfree_rcu
> + * @error: mark this fence with error
> + *
> + */
> +struct hl_fence {
> + struct completion completion;
> + struct kref refcount;
> + struct rcu_head rcu;
> + int error;
> +};
> +
> /**
> * struct hl_cs_compl - command submission completion object.
> - * @base_fence: kernel fence object.
> + * @base_fence: hl fence object.
> * @lock: spinlock to protect fence.
> * @hdev: habanalabs device structure.
> * @hw_sob: the H/W SOB used in this signal/wait CS.
> @@ -353,7 +367,7 @@ struct asic_fixed_properties {
> * @sob_val: the SOB value that is used in this signal/wait CS.
> */
> struct hl_cs_compl {
> - struct dma_fence base_fence;
> + struct hl_fence base_fence;
> spinlock_t lock;
> struct hl_device *hdev;
> struct hl_hw_sob *hw_sob;
> @@ -800,7 +814,7 @@ struct hl_va_range {
> * @hdev: pointer to the device structure.
> * @refcount: reference counter for the context. Context is released only when
> * this hits 0l. It is incremented on CS and CS_WAIT.
> - * @cs_pending: array of DMA fence objects representing pending CS.
> + * @cs_pending: array of hl fence objects representing pending CS.
> * @host_va_range: holds available virtual addresses for host mappings.
> * @host_huge_va_range: holds available virtual addresses for host mappings
> * with huge pages.
> @@ -832,7 +846,7 @@ struct hl_ctx {
> struct hl_fpriv *hpriv;
> struct hl_device *hdev;
> struct kref refcount;
> - struct dma_fence **cs_pending;
> + struct hl_fence **cs_pending;
> struct hl_va_range *host_va_range;
> struct hl_va_range *host_huge_va_range;
> struct hl_va_range *dram_va_range;
> @@ -919,8 +933,8 @@ struct hl_cs {
> struct list_head job_list;
> spinlock_t job_lock;
> struct kref refcount;
> - struct dma_fence *fence;
> - struct dma_fence *signal_fence;
> + struct hl_fence *fence;
> + struct hl_fence *signal_fence;
> struct work_struct finish_work;
> struct delayed_work work_tdr;
> struct list_head mirror_node;
> @@ -1736,7 +1750,7 @@ int hl_ctx_init(struct hl_device *hdev, struct hl_ctx *ctx, bool is_kernel_ctx);
> void hl_ctx_do_release(struct kref *ref);
> void hl_ctx_get(struct hl_device *hdev, struct hl_ctx *ctx);
> int hl_ctx_put(struct hl_ctx *ctx);
> -struct dma_fence *hl_ctx_get_fence(struct hl_ctx *ctx, u64 seq);
> +struct hl_fence *hl_ctx_get_fence(struct hl_ctx *ctx, u64 seq);
> void hl_ctx_mgr_init(struct hl_ctx_mgr *mgr);
> void hl_ctx_mgr_fini(struct hl_device *hdev, struct hl_ctx_mgr *mgr);
>
> @@ -1778,6 +1792,8 @@ void hl_cs_rollback_all(struct hl_device *hdev);
> struct hl_cs_job *hl_cs_allocate_job(struct hl_device *hdev,
> enum hl_queue_type queue_type, bool is_kernel_allocated_cb);
> void hl_sob_reset_error(struct kref *ref);
> +void hl_fence_put(struct hl_fence *fence);
> +void hl_fence_get(struct hl_fence *fence);
>
> void goya_set_asic_funcs(struct hl_device *hdev);
> void gaudi_set_asic_funcs(struct hl_device *hdev);
> diff --git a/drivers/misc/habanalabs/common/hw_queue.c b/drivers/misc/habanalabs/common/hw_queue.c
> index 287681646071..65b9aa69a83e 100644
> --- a/drivers/misc/habanalabs/common/hw_queue.c
> +++ b/drivers/misc/habanalabs/common/hw_queue.c
> @@ -474,7 +474,7 @@ static void init_signal_wait_cs(struct hl_cs *cs)
> * wait CS was submitted.
> */
> mb();
> - dma_fence_put(cs->signal_fence);
> + hl_fence_put(cs->signal_fence);
> cs->signal_fence = NULL;
> }
> }
> --
> 2.17.1
>


--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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