Re: [PATCH] xen/pvcalls-back: fix permanently masked event channel

[Juergen Gross <jgross@xxxxxxxx>]

On 19.01.23 22:11, Volodymyr Babchuk wrote:
> There is a sequence of events that can lead to a permanently masked
> event channel, because xen_irq_lateeoi() is newer called. This happens
> when a backend receives spurious write event from a frontend. In this
> case pvcalls_conn_back_write() returns early and it does not clears the
> map->write counter. As map->write > 0, pvcalls_back_ioworker() returns
> without calling xen_irq_lateeoi(). This leaves the event channel in
> masked state, a backend does not receive any new events from a
> frontend and the whole communication stops.
>
> Move atomic_set(&map->write, 0) to the very beginning of
> pvcalls_conn_back_write() to fix this issue.
>
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
> Reported-by: Oleksii Moisieiev <oleksii_moisieiev@xxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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