Re: [PATCH v3 1/4] rv/reactors: use context-sensitive lockdep wait type in rv_react()
From: Gabriele Monaco <gmonaco@redhat.com>
Date: 2026-08-19 07:12:50
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On Mon, 2026-08-17 at 10:18 +0200, Nam Cao wrote:
Gabriele Monaco [off-list ref] writes:quoted
On Mon, 2026-08-10 at 01:10 +0800, wen.yang@linux.dev wrote:quoted
From: Wen Yang <redacted> Reactors must not explicitly take locks, so they should comply with LD_WAIT_FREE. However, reactor callbacks can run with preemption enabled on any kernel (not just PREEMPT_RT). If a timer interrupt fires during the callback, the interrupt exit path schedules and acquires rq->__lock (LD_WAIT_SPIN) while the lockdep override map that declared LD_WAIT_FREE is still held, triggering a spurious "Invalid wait context" warning:...quoted
Anyway, I'd appreciate comments/acks from the other folks in the loopSorry, I do not know enough about lockdep to comment on this. FWIW, I would rather just use LD_WAIT_SPIN and keep things simple. Context-sensitive code paths "feels wrong" to me. Spinning should either be allowed or forbidden. Making it dynamic "feels like" it will bring further complications down the road. But that's just my intuition.
I don't have a strong opinion on this, but since there's no one in the kernel using LD_WAIT_FREE as inner type, that feels like a hint to go down the simple route too and allow LD_WAIT_SPIN. If a reactor ever uses spinlocks, lockdep would already complain on its own if that ends up being an issue, wouldn't it? Gabriele