[v1] dma-fence: Remove return code of dma_fence_signal() et al.

[PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Philipp Stanner 2 months, 1 week ago

Xe is one of the few users utilizing the return code of
dma_fence_signal() to check whether a fence had already been signaled by
someone else.

To clean up and simplify the dma_fence API, the few kernel users relying
on that behavior shall be ported to an alternative function.

Replace dma_fence_signal_locked() with
dma_fence_check_and_signal_locked().

Signed-off-by: Philipp Stanner <phasta@kernel.org>
---
 drivers/gpu/drm/xe/xe_hw_fence.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_hw_fence.c b/drivers/gpu/drm/xe/xe_hw_fence.c
index b2a0c46dfcd4..f6057456e460 100644
--- a/drivers/gpu/drm/xe/xe_hw_fence.c
+++ b/drivers/gpu/drm/xe/xe_hw_fence.c
@@ -85,7 +85,6 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
 {
 	struct xe_hw_fence *fence, *next;
 	unsigned long flags;
-	int err;
 	bool tmp;
 
 	if (XE_WARN_ON(!list_empty(&irq->pending))) {
@@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
 		spin_lock_irqsave(&irq->lock, flags);
 		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
 			list_del_init(&fence->irq_link);
-			err = dma_fence_signal_locked(&fence->dma);
+			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));
 			dma_fence_put(&fence->dma);
-			XE_WARN_ON(err);
 		}
 		spin_unlock_irqrestore(&irq->lock, flags);
 		dma_fence_end_signalling(tmp);
-- 
2.49.0

Re: [PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Christian König 2 months ago

On 12/1/25 11:50, Philipp Stanner wrote:
> Xe is one of the few users utilizing the return code of
> dma_fence_signal() to check whether a fence had already been signaled by
> someone else.
> 
> To clean up and simplify the dma_fence API, the few kernel users relying
> on that behavior shall be ported to an alternative function.
> 
> Replace dma_fence_signal_locked() with
> dma_fence_check_and_signal_locked().
> 
> Signed-off-by: Philipp Stanner <phasta@kernel.org>

Acked-by: Christian König <christian.koenig@amd.com>

> ---
>  drivers/gpu/drm/xe/xe_hw_fence.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_hw_fence.c b/drivers/gpu/drm/xe/xe_hw_fence.c
> index b2a0c46dfcd4..f6057456e460 100644
> --- a/drivers/gpu/drm/xe/xe_hw_fence.c
> +++ b/drivers/gpu/drm/xe/xe_hw_fence.c
> @@ -85,7 +85,6 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
>  {
>  	struct xe_hw_fence *fence, *next;
>  	unsigned long flags;
> -	int err;
>  	bool tmp;
>  
>  	if (XE_WARN_ON(!list_empty(&irq->pending))) {
> @@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
>  		spin_lock_irqsave(&irq->lock, flags);
>  		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
>  			list_del_init(&fence->irq_link);
> -			err = dma_fence_signal_locked(&fence->dma);
> +			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));
>  			dma_fence_put(&fence->dma);
> -			XE_WARN_ON(err);
>  		}
>  		spin_unlock_irqrestore(&irq->lock, flags);
>  		dma_fence_end_signalling(tmp);

Re: [PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Matthew Brost 2 months, 1 week ago

On Mon, Dec 01, 2025 at 11:50:08AM +0100, Philipp Stanner wrote:
> Xe is one of the few users utilizing the return code of
> dma_fence_signal() to check whether a fence had already been signaled by
> someone else.
> 
> To clean up and simplify the dma_fence API, the few kernel users relying
> on that behavior shall be ported to an alternative function.
> 
> Replace dma_fence_signal_locked() with
> dma_fence_check_and_signal_locked().
> 
> Signed-off-by: Philipp Stanner <phasta@kernel.org>
> ---
>  drivers/gpu/drm/xe/xe_hw_fence.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_hw_fence.c b/drivers/gpu/drm/xe/xe_hw_fence.c
> index b2a0c46dfcd4..f6057456e460 100644
> --- a/drivers/gpu/drm/xe/xe_hw_fence.c
> +++ b/drivers/gpu/drm/xe/xe_hw_fence.c
> @@ -85,7 +85,6 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
>  {
>  	struct xe_hw_fence *fence, *next;
>  	unsigned long flags;
> -	int err;
>  	bool tmp;
>  
>  	if (XE_WARN_ON(!list_empty(&irq->pending))) {
> @@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
>  		spin_lock_irqsave(&irq->lock, flags);
>  		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
>  			list_del_init(&fence->irq_link);
> -			err = dma_fence_signal_locked(&fence->dma);
> +			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));

I think XE_WARN_ON can compile out in certain builds. Best to leave warn on logic as is.

Also a little confused by this new helper... Doesn't
dma_fence_signal_locked already check if a fence is already signaled and
bail? Running out the door so I don't have time dig in here, but can you
explain?

Matt

>  			dma_fence_put(&fence->dma);
> -			XE_WARN_ON(err);
>  		}
>  		spin_unlock_irqrestore(&irq->lock, flags);
>  		dma_fence_end_signalling(tmp);
> -- 
> 2.49.0
>

Re: [PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Andi Shyti 2 months ago

Hi Matt,

> > @@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
> >  		spin_lock_irqsave(&irq->lock, flags);
> >  		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
> >  			list_del_init(&fence->irq_link);
> > -			err = dma_fence_signal_locked(&fence->dma);
> > +			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));
> 
> I think XE_WARN_ON can compile out in certain builds. Best to leave warn on logic as is.

I don't think XE_WARN_ON compiles out. It should always evaluate
the content, then, depending on the build, it prints debug logs.

Andi

Re: [PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Matthew Brost 2 months ago

On Tue, Dec 02, 2025 at 09:47:39PM +0100, Andi Shyti wrote:
> Hi Matt,
> 
> > > @@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
> > >  		spin_lock_irqsave(&irq->lock, flags);
> > >  		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
> > >  			list_del_init(&fence->irq_link);
> > > -			err = dma_fence_signal_locked(&fence->dma);
> > > +			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));
> > 
> > I think XE_WARN_ON can compile out in certain builds. Best to leave warn on logic as is.
> 
> I don't think XE_WARN_ON compiles out. It should always evaluate
> the content, then, depending on the build, it prints debug logs.

Ah, ok. I thought XE_WARN_ON was tied to a Kconfig to compile out or
WARN_ON (this is what XE_WARN_ON resolves) compiled out in some kernel
builds. Upon more looking, I guess neither of these is the case.

So I guess this patch is actually:
Reviewed-by: Matthew Brost <matthew.brost@intel.com>

Sorry for the noise. Side note, we should probably just XE_WARN_ON too
since this is just WARN_ON.

Matt

> 
> Andi

Re: [PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Rodrigo Vivi 2 months ago

On Tue, Dec 02, 2025 at 01:04:24PM -0800, Matthew Brost wrote:
> On Tue, Dec 02, 2025 at 09:47:39PM +0100, Andi Shyti wrote:
> > Hi Matt,
> > 
> > > > @@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
> > > >  		spin_lock_irqsave(&irq->lock, flags);
> > > >  		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
> > > >  			list_del_init(&fence->irq_link);
> > > > -			err = dma_fence_signal_locked(&fence->dma);
> > > > +			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));
> > > 
> > > I think XE_WARN_ON can compile out in certain builds. Best to leave warn on logic as is.
> > 
> > I don't think XE_WARN_ON compiles out. It should always evaluate
> > the content, then, depending on the build, it prints debug logs.
> 
> Ah, ok. I thought XE_WARN_ON was tied to a Kconfig to compile out or
> WARN_ON (this is what XE_WARN_ON resolves) compiled out in some kernel
> builds. Upon more looking, I guess neither of these is the case.
> 
> So I guess this patch is actually:
> Reviewed-by: Matthew Brost <matthew.brost@intel.com>

and

Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

if needed to merge through any other tree...

> 
> Sorry for the noise. Side note, we should probably just XE_WARN_ON too
> since this is just WARN_ON.
> 
> Matt
> 
> > 
> > Andi

Re: [PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Philipp Stanner 2 months, 1 week ago

On Mon, 2025-12-01 at 11:38 -0800, Matthew Brost wrote:
> On Mon, Dec 01, 2025 at 11:50:08AM +0100, Philipp Stanner wrote:
> > Xe is one of the few users utilizing the return code of
> > dma_fence_signal() to check whether a fence had already been signaled by
> > someone else.
> > 
> > To clean up and simplify the dma_fence API, the few kernel users relying
> > on that behavior shall be ported to an alternative function.
> > 
> > Replace dma_fence_signal_locked() with
> > dma_fence_check_and_signal_locked().
> > 
> > Signed-off-by: Philipp Stanner <phasta@kernel.org>
> > ---
> >  drivers/gpu/drm/xe/xe_hw_fence.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_hw_fence.c b/drivers/gpu/drm/xe/xe_hw_fence.c
> > index b2a0c46dfcd4..f6057456e460 100644
> > --- a/drivers/gpu/drm/xe/xe_hw_fence.c
> > +++ b/drivers/gpu/drm/xe/xe_hw_fence.c
> > @@ -85,7 +85,6 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
> >  {
> >  	struct xe_hw_fence *fence, *next;
> >  	unsigned long flags;
> > -	int err;
> >  	bool tmp;
> >  
> >  	if (XE_WARN_ON(!list_empty(&irq->pending))) {
> > @@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
> >  		spin_lock_irqsave(&irq->lock, flags);
> >  		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
> >  			list_del_init(&fence->irq_link);
> > -			err = dma_fence_signal_locked(&fence->dma);
> > +			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));
> 
> I think XE_WARN_ON can compile out in certain builds. Best to leave warn on logic as is.

OK, will adjust.

> 
> Also a little confused by this new helper... Doesn't
> dma_fence_signal_locked already check if a fence is already signaled and
> bail? Running out the door so I don't have time dig in here, but can you
> explain?

Yes, that is what dma_fence_signal_locked() *currently* does. The
series, however, is about removing that check from the default
interfaces because barely anyone uses dma_fence_signal() et.al.'s
return code. To simplify the interfaces.
The 2-3 users who need the code get this new function. See cover
letter.


P.

> 
> Matt
> 
> >  			dma_fence_put(&fence->dma);
> > -			XE_WARN_ON(err);
> >  		}
> >  		spin_unlock_irqrestore(&irq->lock, flags);
> >  		dma_fence_end_signalling(tmp);
> > -- 
> > 2.49.0
> >

Re: [PATCH v2 4/8] drm/xe: Use dma_fence_check_and_signal_locked()

Posted by Matthew Brost 2 months, 1 week ago

On Tue, Dec 02, 2025 at 08:17:17AM +0100, Philipp Stanner wrote:
> On Mon, 2025-12-01 at 11:38 -0800, Matthew Brost wrote:
> > On Mon, Dec 01, 2025 at 11:50:08AM +0100, Philipp Stanner wrote:
> > > Xe is one of the few users utilizing the return code of
> > > dma_fence_signal() to check whether a fence had already been signaled by
> > > someone else.
> > > 
> > > To clean up and simplify the dma_fence API, the few kernel users relying
> > > on that behavior shall be ported to an alternative function.
> > > 
> > > Replace dma_fence_signal_locked() with
> > > dma_fence_check_and_signal_locked().
> > > 
> > > Signed-off-by: Philipp Stanner <phasta@kernel.org>
> > > ---
> > >  drivers/gpu/drm/xe/xe_hw_fence.c | 4 +---
> > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/xe/xe_hw_fence.c b/drivers/gpu/drm/xe/xe_hw_fence.c
> > > index b2a0c46dfcd4..f6057456e460 100644
> > > --- a/drivers/gpu/drm/xe/xe_hw_fence.c
> > > +++ b/drivers/gpu/drm/xe/xe_hw_fence.c
> > > @@ -85,7 +85,6 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
> > >  {
> > >  	struct xe_hw_fence *fence, *next;
> > >  	unsigned long flags;
> > > -	int err;
> > >  	bool tmp;
> > >  
> > >  	if (XE_WARN_ON(!list_empty(&irq->pending))) {
> > > @@ -93,9 +92,8 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq)
> > >  		spin_lock_irqsave(&irq->lock, flags);
> > >  		list_for_each_entry_safe(fence, next, &irq->pending, irq_link) {
> > >  			list_del_init(&fence->irq_link);
> > > -			err = dma_fence_signal_locked(&fence->dma);
> > > +			XE_WARN_ON(dma_fence_check_and_signal_locked(&fence->dma));
> > 
> > I think XE_WARN_ON can compile out in certain builds. Best to leave warn on logic as is.
> 
> OK, will adjust.
> 
> > 
> > Also a little confused by this new helper... Doesn't
> > dma_fence_signal_locked already check if a fence is already signaled and
> > bail? Running out the door so I don't have time dig in here, but can you
> > explain?
> 
> Yes, that is what dma_fence_signal_locked() *currently* does. The
> series, however, is about removing that check from the default
> interfaces because barely anyone uses dma_fence_signal() et.al.'s
> return code. To simplify the interfaces.
> The 2-3 users who need the code get this new function. See cover
> letter.
> 

Thanks for explaination. This should work then with XE_WARN_ON refactor.

Matt

> 
> P.
> 
> > 
> > Matt
> > 
> > >  			dma_fence_put(&fence->dma);
> > > -			XE_WARN_ON(err);
> > >  		}
> > >  		spin_unlock_irqrestore(&irq->lock, flags);
> > >  		dma_fence_end_signalling(tmp);
> > > -- 
> > > 2.49.0
> > > 
>