linux-kernel - Re: 5.13-rt1 + KVM = WARNING: at fs/eventfd.c:74 eventfd

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Date:   Fri, 16 Jul 2021 08:54:58 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Juri Lelli <jlelli@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        He Zhe <zhe.he@...driver.com>
Subject: Re: 5.13-rt1 + KVM = WARNING: at fs/eventfd.c:74 eventfd_signal()

On 16/07/21 04:06, Hillf Danton wrote:
>> With the patch:
>> 	- no warn
>> 	- continue using the VM normally...
> Well with the patch applied, the VM works fine without the stuff protected
> by the spin_lock_irqsave(), then without the patch why simply printing a
> warning makes the VM dumb, given the warning is there actually also preventing
> you from touching the lock.
> 

If the warning is triggered, eventfd_signal will not do the wakeup.

Paolo