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Date: Tue, 12 May 2026 08:07:58 -1000
Message-ID: <056f95bc5805f7e161458984fff4b3cb@kernel.org>
From: Tejun Heo <tj@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Ben Segall <bsegall@google.com>,
	Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Kyle McMartin <jkkm@meta.com>,
	linux-kernel@vger.kernel.org,
	stable@vger.kernel.org,
	Linux RT Development <linux-rt-devel@lists.linux.dev>,
	Clark Williams <williams@redhat.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	John Kacur <jkacur@redhat.com>
Subject: Re: [PATCH sched/core] sched/rt: Fix RT_PUSH_IPI soft lockup loop
In-Reply-To: <20260512113754.448c1f5b@gandalf.local.home>
References: <20260506235716.2530720-1-tj@kernel.org>
 <20260507141437.GJ3102624@noisy.programming.kicks-ass.net>
 <20260512113754.448c1f5b@gandalf.local.home>
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Hello,

Looking at 49bef33e4b87 ("sched/rt: Plug rt_mutex_setprio() vs
push_rt_task() race"), the prio bail looks like it was already there
and only got moved up to retry:. For non-migration-disabled next_task
the bail fires at the same effective point both before and after, and
rto_push_irq_work_func() + rto_next_cpu() were already in their
current shape, so the loop seems reachable before the move too -
b6366f048e0c ("sched/rt: Use IPI to trigger RT task push migration
instead of pulling") looks like the actual origin.

Am I reading it wrong?

Thanks.

--
tejun