On 13.03.24 09:14, Juergen Gross wrote:
Hello Juergen
> When unbinding a user event channel, the related handler might be
> called a last time in case the kernel was built with
> CONFIG_DEBUG_SHIRQ. This might cause a WARN() in the handler.
>
> Avoid that by adding an "unbinding" flag to struct user_event which
> will short circuit the handler.
>
> Fixes: 9e90e58c11b7 ("xen: evtchn: Allow shared registration of IRQ handers")
> Reported-by: Demi Marie Obenour <d...@invisiblethingslab.com>
> Tested-by: Demi Marie Obenour <d...@invisiblethingslab.com>
> Signed-off-by: Juergen Gross <jgr...@suse.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshche...@epam.com>
> ---
> drivers/xen/evtchn.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
> index 59717628ca42..f6a2216c2c87 100644
> --- a/drivers/xen/evtchn.c
> +++ b/drivers/xen/evtchn.c
> @@ -85,6 +85,7 @@ struct user_evtchn {
> struct per_user_data *user;
> evtchn_port_t port;
> bool enabled;
> + bool unbinding;
> };
>
> static void evtchn_free_ring(evtchn_port_t *ring)
> @@ -164,6 +165,10 @@ static irqreturn_t evtchn_interrupt(int irq, void *data)
> struct per_user_data *u = evtchn->user;
> unsigned int prod, cons;
>
> + /* Handler might be called when tearing down the IRQ. */
> + if (evtchn->unbinding)
> + return IRQ_HANDLED;
> +
> WARN(!evtchn->enabled,
> "Interrupt for port %u, but apparently not enabled; per-user %p\n",
> evtchn->port, u);
> @@ -421,6 +426,7 @@ static void evtchn_unbind_from_user(struct per_user_data
> *u,
>
> BUG_ON(irq < 0);
>
> + evtchn->unbinding = true;
> unbind_from_irqhandler(irq, evtchn);
>
> del_evtchn(u, evtchn);
