[PATCH RT 09/10] drm/i915/gt: Queue and wait for the irq_work item.

From: Steven Rostedt
Date: Mon Nov 22 2021 - 15:39:32 EST

5.10.78-rt56-rc2 stable review patch.
If anyone has any objections, please let me know.


From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Disabling interrupts and invoking the irq_work function directly breaks
PREEMPT_RT does not invoke all irq_work from hardirq context because
some of the user have spinlock_t locking in the callback function.
These locks are then turned into a sleeping locks which can not be
acquired with disabled interrupts.

Using irq_work_queue() has the benefit that the irqwork will be invoked
in the regular context. In general there is "no" delay between enqueuing
the callback and its invocation because the interrupt is raised right
away on architectures which support it (which includes x86).

Use irq_work_queue() + irq_work_sync() instead invoking the callback

Reported-by: Clark Williams <williams@xxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index 0040b4765a54..3f4f854786f2 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -342,10 +342,9 @@ void intel_breadcrumbs_park(struct intel_breadcrumbs *b)
/* Kick the work once more to drain the signalers */
while (unlikely(READ_ONCE(b->irq_armed))) {
- local_irq_disable();
- signal_irq_work(&b->irq_work);
- local_irq_enable();
+ irq_work_queue(&b->irq_work);
+ irq_work_sync(&b->irq_work);