From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>,
linux-kernel@vger.kernel.org, rcu@vger.kernel.org,
stable-rt <stable-rt@vger.kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Davidlohr Bueso <dave@stgolabs.net>,
Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Thomas Gleixner <tglx@linutronix.de>,
Florian Bezdeka <florian.bezdeka@siemens.com>,
Pavel Machek <pavel@denx.de>
Subject: Re: [PATCH v3 3/3] softirq: Use a dedicated thread for timer wakeups on PREEMPT_RT.
Date: Tue, 2 Dec 2025 09:22:06 +0100 [thread overview]
Message-ID: <20251202082206.EnnTU37J@linutronix.de> (raw)
In-Reply-To: <00552531-d00a-4e29-898c-86f4474b12a7@siemens.com>
On 2025-12-02 07:57:04 [+0100], Jan Kiszka wrote:
> So, we have this right now in the 6.12-rt and 6.1-rt trees. The patch
> (b12e35832805) that enabled the lockup above was added to 4.18. In
> 4.19-rt (still under maintenance via 4.19-cip-rt), we had ktimersoftd -
> was that addressing the issue as well? Or could timers have expired back
> then also outside of that thread, thus potentially without SCHED_FIFO prio?
Looking at v4.19.25-rt16, there is ktimersoftd/ via "softirq: split
timer softirqs out of ksoftirqd". This became later ktimers/.
So yes, the timer should be expired with a SCHED_FIFO priority.
You are most likely aware of "Defer throttle when task exits to user"
https://lore.kernel.org/all/20250829081120.806-1-ziqianlu@bytedance.com/
> Thanks,
> Jan
Sebastian
next prev parent reply other threads:[~2025-12-02 8:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-06 14:51 PATCH v3 0/3] softirq: Use a dedicated thread for timer wakeups with forced-threading Sebastian Andrzej Siewior
2024-11-06 14:51 ` [PATCH v3 1/3] hrtimer: Use __raise_softirq_irqoff() to raise the softirq Sebastian Andrzej Siewior
2024-11-07 1:48 ` [tip: irq/core] " tip-bot2 for Sebastian Andrzej Siewior
2024-11-06 14:51 ` [PATCH v3 2/3] timers: " Sebastian Andrzej Siewior
2024-11-07 1:48 ` [tip: irq/core] " tip-bot2 for Sebastian Andrzej Siewior
2024-11-06 14:51 ` [PATCH v3 3/3] softirq: Use a dedicated thread for timer wakeups on PREEMPT_RT Sebastian Andrzej Siewior
2024-11-07 1:48 ` [tip: irq/core] " tip-bot2 for Sebastian Andrzej Siewior
2025-12-01 21:51 ` [PATCH v3 3/3] " Jan Kiszka
2025-12-01 23:49 ` Luis Claudio R. Goncalves
2025-12-02 6:57 ` Jan Kiszka
2025-12-02 8:22 ` Sebastian Andrzej Siewior [this message]
2025-12-02 8:24 ` Sebastian Andrzej Siewior
2025-12-02 12:39 ` Jan Kiszka
2025-12-02 13:22 ` Sebastian Andrzej Siewior
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