| Message ID | 20200616195053.99253-4-farman@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vfio-ccw: Fix interrupt handling for HALT/CLEAR | expand |
On Tue, 16 Jun 2020 21:50:53 +0200 Eric Farman <farman@linux.ibm.com> wrote: > When an interrupt is received via the IRQ, the bulk of the work is > stacked on a workqueue for later processing. Which means that concurrent > START or a HALT/CLEAR operation (via the async_region) will race with > this process and require some serialization. > > Once we have all our locks acquired, let's just look to see if we're > in a window where the process has been started from the IRQ, but not > yet picked up by vfio-ccw to clean up an I/O. If there is, mark the > request as BUSY so it can be redriven after we have a chance to breathe. This change looks reasonable to me. It would be even better if we could send off I/O requests at any time; but if signaling to retry saves us from some hairy code elsewhere, it is a good idea to do so. > > Signed-off-by: Eric Farman <farman@linux.ibm.com> > --- > drivers/s390/cio/vfio_ccw_fsm.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c > index f0952192480e..9dc5b4d549b3 100644 > --- a/drivers/s390/cio/vfio_ccw_fsm.c > +++ b/drivers/s390/cio/vfio_ccw_fsm.c > @@ -28,6 +28,11 @@ static int fsm_io_helper(struct vfio_ccw_private *private) > > spin_lock_irqsave(sch->lock, flags); > > + if (work_pending(&private->io_work)) { > + ret = -EBUSY; > + goto out; > + } > + > orb = cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm); > if (!orb) { > ret = -EIO;
diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c index f0952192480e..9dc5b4d549b3 100644 --- a/drivers/s390/cio/vfio_ccw_fsm.c +++ b/drivers/s390/cio/vfio_ccw_fsm.c @@ -28,6 +28,11 @@ static int fsm_io_helper(struct vfio_ccw_private *private) spin_lock_irqsave(sch->lock, flags); + if (work_pending(&private->io_work)) { + ret = -EBUSY; + goto out; + } + orb = cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm); if (!orb) { ret = -EIO;
When an interrupt is received via the IRQ, the bulk of the work is stacked on a workqueue for later processing. Which means that concurrent START or a HALT/CLEAR operation (via the async_region) will race with this process and require some serialization. Once we have all our locks acquired, let's just look to see if we're in a window where the process has been started from the IRQ, but not yet picked up by vfio-ccw to clean up an I/O. If there is, mark the request as BUSY so it can be redriven after we have a chance to breathe. Signed-off-by: Eric Farman <farman@linux.ibm.com> --- drivers/s390/cio/vfio_ccw_fsm.c | 5 +++++ 1 file changed, 5 insertions(+)