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From: Tejun Heo <tj@kernel.org>
To: Christian Loehle <christian.loehle@arm.com>
Cc: sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, void@manifault.com,
	arighi@nvidia.com, changwoo@igalia.com, mingo@redhat.com,
	peterz@infradead.org, shuah@kernel.org, dietmar.eggemann@arm.com
Subject: Re: [PATCH 1/2] sched_ext: Prevent SCX_KICK_WAIT deadlock by serialization
Date: Mon, 16 Mar 2026 07:46:09 -1000	[thread overview]
Message-ID: <abhB4bCsvd9WDxid@slm.duckdns.org> (raw)
In-Reply-To: <20260316100249.1651641-2-christian.loehle@arm.com>

Hello,

On Mon, Mar 16, 2026 at 10:02:48AM +0000, Christian Loehle wrote:
> @@ -5686,11 +5718,20 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
>  		 * task is picked subsequently. The latter is necessary to break
>  		 * the wait when $cpu is taken by a higher sched class.
>  		 */
> -		if (cpu != cpu_of(this_rq))
> +		if (cpu != this_cpu)
>  			smp_cond_load_acquire(wait_kick_sync, VAL != ksyncs[cpu]);

Given that irq_work is executed at the end of IRQ handling, we can just
reschedule the irq work when the condition is not met (or separate that out
into its own irq_work). That way, I think we can avoid the global lock.

Thanks.

-- 
tejun

  parent reply	other threads:[~2026-03-16 17:46 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-16 10:02 [PATCH 0/2] sched_ext: Fix SCX_KICK_WAIT cycle deadlock Christian Loehle
2026-03-16 10:02 ` [PATCH 1/2] sched_ext: Prevent SCX_KICK_WAIT deadlock by serialization Christian Loehle
2026-03-16 10:49   ` Andrea Righi
2026-03-16 11:12     ` Christian Loehle
2026-03-16 14:42       ` Andrea Righi
2026-03-16 17:46   ` Tejun Heo [this message]
2026-03-16 22:26     ` Christian Loehle
2026-03-17  8:23       ` Christian Loehle
2026-03-17  9:15         ` Christian Loehle
2026-03-16 10:02 ` [PATCH 2/2] sched_ext/selftests: Add SCX_KICK_WAIT cycle tests Christian Loehle
2026-03-29  0:20 ` [PATCH 1/2] sched_ext: Prevent SCX_KICK_WAIT deadlock by serialization Tejun Heo

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