linux-kernel - Re: [PATCH v3] drm/xe: Replace use of system_wq with tlb_inval->timeout

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Message-ID: <aWdKdllO8ZTRfYgp@lstrano-desk.jf.intel.com>
Date: Tue, 13 Jan 2026 23:49:10 -0800
From: Matthew Brost <matthew.brost@...el.com>
To: Marco Crivellari <marco.crivellari@...e.com>
CC: <linux-kernel@...r.kernel.org>, <intel-xe@...ts.freedesktop.org>,
	<dri-devel@...ts.freedesktop.org>, Tejun Heo <tj@...nel.org>, Lai Jiangshan
	<jiangshanlai@...il.com>, Frederic Weisbecker <frederic@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Michal Hocko
	<mhocko@...e.com>, Thomas Hellstrom <thomas.hellstrom@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Subject: Re: [PATCH v3] drm/xe: Replace use of system_wq with
 tlb_inval->timeout_wq

On Mon, Jan 12, 2026 at 06:54:46PM -0800, Matthew Brost wrote:
> On Mon, Jan 12, 2026 at 10:44:06AM +0100, Marco Crivellari wrote:
> > This patch continues the effort to refactor workqueue APIs, which has begun
> > with the changes introducing new workqueues and a new alloc_workqueue flag:
> > 
> >    commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
> >    commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")
> > 
> > The point of the refactoring is to eventually alter the default behavior of
> > workqueues to become unbound by default so that their workload placement is
> > optimized by the scheduler.
> > 
> > Before that to happen, workqueue users must be converted to the better named
> > new workqueues with no intended behaviour changes:
> > 
> >    system_wq -> system_percpu_wq
> >    system_unbound_wq -> system_dfl_wq
> > 
> > This way the old obsolete workqueues (system_wq, system_unbound_wq) can be
> > removed in the future.
> > 
> > After a carefully evaluation, because this is the fence signaling path, we
> > changed the code in order to use one of the Xe's workqueue.
> > 
> > So, a new workqueue named 'timeout_wq' has been added to
> > 'struct xe_tlb_inval' and has been initialized with 'gt->ordered_wq'
> > changing the system_wq uses with tlb_inval->timeout_wq.
> > 
> > Link: https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
> > Suggested-by: Tejun Heo <tj@...nel.org>
> > Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
> 
> Reviewed-by: Matthew Brost <matthew.brost@...el.com>
> 

Merged to drm-xe-next, thanks for the patch.

Matt

> > ---
> > Changes in v3:
> > - refactoring workqueue name from fence_signal_wq to timeout_wq.
> > 
> > - rebased on v6.19-rc5.
> > 
> > Changes in v2:
> > - added 'fence_signal_wq', initialized with 'gt->ordered_wq' in order to use
> >   it in the fence signaling path, instead of system_wq.
> > 
> > - rebased on v6.19-rc4.
> > 
> > 
> >  drivers/gpu/drm/xe/xe_tlb_inval.c       | 10 +++++++---
> >  drivers/gpu/drm/xe/xe_tlb_inval_types.h |  2 ++
> >  2 files changed, 9 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_tlb_inval.c b/drivers/gpu/drm/xe/xe_tlb_inval.c
> > index 918a59e686ea..084d996b818d 100644
> > --- a/drivers/gpu/drm/xe/xe_tlb_inval.c
> > +++ b/drivers/gpu/drm/xe/xe_tlb_inval.c
> > @@ -94,7 +94,7 @@ static void xe_tlb_inval_fence_timeout(struct work_struct *work)
> >  		xe_tlb_inval_fence_signal(fence);
> >  	}
> >  	if (!list_empty(&tlb_inval->pending_fences))
> > -		queue_delayed_work(system_wq, &tlb_inval->fence_tdr,
> > +		queue_delayed_work(tlb_inval->timeout_wq, &tlb_inval->fence_tdr,
> >  				   timeout_delay);
> >  	spin_unlock_irq(&tlb_inval->pending_lock);
> >  }
> > @@ -146,6 +146,10 @@ int xe_gt_tlb_inval_init_early(struct xe_gt *gt)
> >  	if (IS_ERR(tlb_inval->job_wq))
> >  		return PTR_ERR(tlb_inval->job_wq);
> >  
> > +	tlb_inval->timeout_wq = gt->ordered_wq;
> > +	if (IS_ERR(tlb_inval->timeout_wq))
> > +		return PTR_ERR(tlb_inval->timeout_wq);
> > +
> >  	/* XXX: Blindly setting up backend to GuC */
> >  	xe_guc_tlb_inval_init_early(&gt->uc.guc, tlb_inval);
> >  
> > @@ -226,7 +230,7 @@ static void xe_tlb_inval_fence_prep(struct xe_tlb_inval_fence *fence)
> >  	list_add_tail(&fence->link, &tlb_inval->pending_fences);
> >  
> >  	if (list_is_singular(&tlb_inval->pending_fences))
> > -		queue_delayed_work(system_wq, &tlb_inval->fence_tdr,
> > +		queue_delayed_work(tlb_inval->timeout_wq, &tlb_inval->fence_tdr,
> >  				   tlb_inval->ops->timeout_delay(tlb_inval));
> >  	spin_unlock_irq(&tlb_inval->pending_lock);
> >  
> > @@ -378,7 +382,7 @@ void xe_tlb_inval_done_handler(struct xe_tlb_inval *tlb_inval, int seqno)
> >  	}
> >  
> >  	if (!list_empty(&tlb_inval->pending_fences))
> > -		mod_delayed_work(system_wq,
> > +		mod_delayed_work(tlb_inval->timeout_wq,
> >  				 &tlb_inval->fence_tdr,
> >  				 tlb_inval->ops->timeout_delay(tlb_inval));
> >  	else
> > diff --git a/drivers/gpu/drm/xe/xe_tlb_inval_types.h b/drivers/gpu/drm/xe/xe_tlb_inval_types.h
> > index 8f8b060e9005..e5ff35226826 100644
> > --- a/drivers/gpu/drm/xe/xe_tlb_inval_types.h
> > +++ b/drivers/gpu/drm/xe/xe_tlb_inval_types.h
> > @@ -106,6 +106,8 @@ struct xe_tlb_inval {
> >  	struct workqueue_struct *job_wq;
> >  	/** @tlb_inval.lock: protects TLB invalidation fences */
> >  	spinlock_t lock;
> > +	/** @timeout_wq: schedules TLB invalidation fence timeouts */
> > +	struct workqueue_struct *timeout_wq;
> >  };
> >  
> >  /**
> > -- 
> > 2.52.0
> >