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From: Nam Cao <namcao@linutronix.de>
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To: Wen Yang <wen.yang@linux.dev>, Thomas =?utf-8?Q?Wei=C3=9Fschuh?=
 <thomas.weissschuh@linutronix.de>, Gabriele Monaco <gmonaco@redhat.com>
Cc: linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] rv/reactors: fix lockdep "Invalid wait context" in
 rv_react()
In-Reply-To: <397cea12-e0ba-4cf5-a411-26f44bc17d01@linux.dev>
References: <cover.1781541556.git.wen.yang@linux.dev>
 <bc01343ae74acf6bdf142434aeaa4e6b40aa72a9.1781541556.git.wen.yang@linux.dev>
 <20260623112942-4943fc6a-c1d5-4eed-a91f-66b3a034caa7@linutronix.de>
 <3c53f741559f834986e976b524c5ded90bbd5627.camel@redhat.com>
 <20260708174123-e5f98837-3d81-43ca-8ede-bb5f09e8ffba@linutronix.de>
 <397cea12-e0ba-4cf5-a411-26f44bc17d01@linux.dev>
Date: Thu, 09 Jul 2026 20:07:54 +0200
Message-ID: <87y0fkdojp.fsf@yellow.woof>
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Wen Yang <wen.yang@linux.dev> writes:
> How about a context-sensitive approach, eg:
>
>    NMI/hardirq (interrupts masked, scheduler cannot run):
>      Keep LD_WAIT_FREE.  The false positive cannot arise in this path,
>      and the original constraint against raw spinlocks is preserved where
>      it is meaningful.
>
>    task/softirq/PREEMPT_RT irq thread (preemptible):
>      Raise to LD_WAIT_SPIN.  Raw spinlocks become permitted =E2=80=94 as =
Gabriele
>      note, this is a necessary consequence of any fix in this path.

I don't get the point. Unless the lock's type is also context-sensitive,
the reactors still cannot use raw spin locks.

Nam