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Re: [PATCH 0/2] Re-raise irq_work lost during Xen suspend
- To: Julian Vetter <julian@xxxxxxxxxxxxxxxx>, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
- From: Adrian Hunter <adrian.hunter@xxxxxxxxx>
- Date: Mon, 9 Nov 2026 12:56:24 +0200
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- Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>, "Juergen Gross" <jgross@xxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>, Jiayuan Chen <jiayuan.chen@xxxxxxxxx>, "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>, "Vineeth Pillai (Google)" <vineeth@xxxxxxxxxxxxxxx>
- Delivery-date: Mon, 09 Nov 2026 11:12:08 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 09/11/2026 12:16, Julian Vetter wrote:
> On 11/6/26 4:39 PM, Sebastian Andrzej Siewior wrote:
>>
>> Looking at #1, you could probably limit it to a nop on
>> !arch_irq_work_has_interrupt(). The tick should not be disabled if
>> irq_work_needs_cpu() returns true (you don't add anything).
>>
>
> Yes, right, the lazy part is pointless.
>
>> And lazy items get handled via irq_work_tick() anyway. This make me
>> think if it gets any easier if we handle both in irq_work_tick(). On x86
>> raised_list is evaluated anyway so by dropping
>> arch_irq_work_has_interrupt() we would avoid the APIC check and handle
>> list in this rare case. If the IRQ-work is working then the list remains
>> empty.
>>
>
> This is maybe a cleaner solution, it needs no APIC access and no call site in
> the suspend paths. But irq_work_needs_cpu() would need the same change,
> otherwise in a CONFIG_NOHZ=y setting an idle CPU would still sit on the work
> until it leaves idle and re-enables the timer tick, no? I will test this.
A fix for stable is needed, so need to check that there is no
irq_work that would have a problem running in the tick context.
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