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authorFarhan Ali <alifm@linux.ibm.com>2019-04-16 17:23:14 -0400
committerCornelia Huck <cohuck@redhat.com>2019-04-24 14:18:51 +0200
commitd1ffa760d22aa1d8190478e5ef555c59a771db27 (patch)
tree67987d48a04ed0d51f6fa68be7f3972213295bc8
parentb49bdc8602b7c9c7a977758bee4125683f73e59f (diff)
vfio-ccw: Prevent quiesce function going into an infinite loop
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>
-rw-r--r--drivers/s390/cio/vfio_ccw_drv.c32
1 files changed, 18 insertions, 14 deletions
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index d72aa8c760c5..ee8767f5845a 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -43,26 +43,30 @@ 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: