[ Upstream commit d1ffa760d22aa1d8190478e5ef555c59a771db27 ]
The quiesce function calls cio_cancel_halt_clear() and if we get an -EBUSY we go into a loop where we: - wait for any interrupts - flush all I/O in the workqueue - retry cio_cancel_halt_clear
During the period where we are waiting for interrupts or flushing all I/O, the channel subsystem could have completed a halt/clear action and turned off the corresponding activity control bits in the subchannel status word. This means the next time we call cio_cancel_halt_clear(), we will again start by calling cancel subchannel and so we can be stuck between calling cancel and halt forever.
Rather than calling cio_cancel_halt_clear() immediately after waiting, let's try to disable the subchannel. If we succeed in disabling the subchannel then we know nothing else can happen with the device.
Suggested-by: Eric Farman farman@linux.ibm.com Signed-off-by: Farhan Ali alifm@linux.ibm.com Message-Id: 4d5a4b98ab1b41ac6131b5c36de18b76c5d66898.1555449329.git.alifm@linux.ibm.com Reviewed-by: Eric Farman farman@linux.ibm.com Acked-by: Halil Pasic pasic@linux.ibm.com Signed-off-by: Cornelia Huck cohuck@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/s390/cio/vfio_ccw_drv.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c index 59eb5e6d9c79d..6cd41086f23e4 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -38,26 +38,30 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch) if (ret != -EBUSY) goto out_unlock;
+ iretry = 255; do { - iretry = 255;
ret = cio_cancel_halt_clear(sch, &iretry); - while (ret == -EBUSY) { - /* - * Flush all I/O and wait for - * cancel/halt/clear completion. - */ - private->completion = &completion; - spin_unlock_irq(sch->lock);
- wait_for_completion_timeout(&completion, 3*HZ); + if (ret == -EIO) { + pr_err("vfio_ccw: could not quiesce subchannel 0.%x.%04x!\n", + sch->schid.ssid, sch->schid.sch_no); + break; + } + + /* + * Flush all I/O and wait for + * cancel/halt/clear completion. + */ + private->completion = &completion; + spin_unlock_irq(sch->lock);
- private->completion = NULL; - flush_workqueue(vfio_ccw_work_q); - spin_lock_irq(sch->lock); - ret = cio_cancel_halt_clear(sch, &iretry); - }; + if (ret == -EBUSY) + wait_for_completion_timeout(&completion, 3*HZ);
+ private->completion = NULL; + flush_workqueue(vfio_ccw_work_q); + spin_lock_irq(sch->lock); ret = cio_disable_subchannel(sch); } while (ret == -EBUSY); out_unlock: