serial: Fix race for IOCTL_SERIAL_WAIT_ON_MASK

[Alexandre Julliard]

Wolfgang Walter <wolfgang.walter at stwm.de> writes:

> set status field of piosb to STATUS_PENDING before calling wait_on(). If wait_on
> returns with STATUS_PENDING don't touch piosb.
>
> Reason: if wait_on returns with STATUS_PENDING it started a thread which
> itself modifies the status field.

In general the iosb is not modified until the operation completes.

-- 
Alexandre Julliard
julliard at winehq.org