linux-kernel - Re: [PATCH v4 09/10] workqueue: Implement system-wide nr_active enforcement for unbound workqueues

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Date: Tue, 30 Jan 2024 18:24:51 -1000
From: Tejun Heo <tj@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	linux-kernel@...r.kernel.org, Naohiro.Aota@....com,
	kernel-team@...a.com
Subject: Re: [PATCH v4 09/10] workqueue: Implement system-wide nr_active
 enforcement for unbound workqueues

On Tue, Jan 30, 2024 at 09:20:31PM -0700, Nathan Chancellor wrote:
> On Tue, Jan 30, 2024 at 06:13:02PM -1000, Tejun Heo wrote:
> > On Tue, Jan 30, 2024 at 09:12:05PM -0700, Nathan Chancellor wrote:
> > > Hi Tejun,
> > > 
> > > On Tue, Jan 30, 2024 at 06:02:52PM -1000, Tejun Heo wrote:
> > > > Hello,
> > > > 
> > > > Thanks for the report. Can you please test whether the following patch fixes
> > > > the problem?
> > > 
> > > I just tested this change on top of 5797b1c18919 but it does not appear
> > > to resolve the issue for any of the three configurations that I tested.
> > 
> > Bummer. Can you map the faulting address to the source line?
> 
> Sure, here is the arm64 stacktrace run through
> scripts/decode_stacktrace.sh, the line numbers correspond to your tree
> at 5797b1c18919.

Ah, I see. How about the following?

Thanks.

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9221a4c57ae1..31c1373505d8 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1510,7 +1510,7 @@ static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu)
 
 	lockdep_assert_held(&wq->mutex);
 
-	if (!cpumask_test_cpu(off_cpu, effective))
+	if (off_cpu >= 0 && !cpumask_test_cpu(off_cpu, effective))
 		off_cpu = -1;
 
 	total_cpus = cpumask_weight_and(effective, cpu_online_mask);

-- 
tejun