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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
	linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Carsten Emde <C.Emde@osadl.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	John Kacur <jkacur@redhat.com>, Daniel Wagner <wagi@monom.org>,
	Tom Zanussi <zanussi@kernel.org>,
	"Srivatsa S. Bhat" <srivatsa@csail.mit.edu>,
	Clark Williams <williams@redhat.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Subject: [PATCH RT 09/10] drm/i915/gt: Queue and wait for the irq_work item.
Date: Mon, 22 Nov 2021 15:38:56 -0500	[thread overview]
Message-ID: <20211122203905.001687595@goodmis.org> (raw)
In-Reply-To: <20211122203847.390551309@goodmis.org>

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

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Disabling interrupts and invoking the irq_work function directly breaks
on PREEMPT_RT.
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
directly.

Reported-by: Clark Williams <williams@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 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 */
 	irq_work_sync(&b->irq_work);
 	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);
 		cond_resched();
+		irq_work_sync(&b->irq_work);
 	}
 	GEM_BUG_ON(!list_empty(&b->signalers));
 }
-- 
2.33.0

  parent reply	other threads:[~2021-11-22 20:39 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-22 20:38 [PATCH RT 00/10] Linux 5.10.78-rt56-rc2 Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 01/10] mm, zsmalloc: Convert zsmalloc_handle.lock to spinlock_t Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 02/10] sched: Fix get_push_task() vs migrate_disable() Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 03/10] sched: Switch wait_task_inactive to HRTIMER_MODE_REL_HARD Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 04/10] preempt: Move preempt_enable_no_resched() to the RT block Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 05/10] mm: Disable NUMA_BALANCING_DEFAULT_ENABLED and TRANSPARENT_HUGEPAGE on PREEMPT_RT Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 06/10] fscache: Use only one fscache_object_cong_wait Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 07/10] fscache: Use only one fscache_object_cong_wait (2) Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 08/10] locking: Drop might_resched() from might_sleep_no_state_check() Steven Rostedt
2021-11-22 20:38 ` Steven Rostedt [this message]
2021-11-23  8:25   ` [PATCH RT 09/10] drm/i915/gt: Queue and wait for the irq_work item Sebastian Andrzej Siewior
2021-11-23 15:37     ` Steven Rostedt
2021-11-24 16:12       ` Sebastian Andrzej Siewior
2021-11-24 16:12         ` [PATCH RT 1/3] irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support Sebastian Andrzej Siewior
2021-11-24 16:12         ` [PATCH RT 2/3] irq_work: Handle some irq_work in a per-CPU thread on PREEMPT_RT Sebastian Andrzej Siewior
2021-11-24 16:12         ` [PATCH RT 3/3] irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ " Sebastian Andrzej Siewior
2021-11-22 20:38 ` [PATCH RT 10/10] Linux 5.10.78-rt56-rc2 Steven Rostedt

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