From: Farhan Ali <alifm@linux.ibm.com>
To: kvm@vger.kernel.org, linux-s390@vger.kernel.org
Cc: cohuck@redhat.com, farman@linux.ibm.com, pasic@linux.ibm.com,
pmorel@linux.ibm.com, alifm@linux.ibm.com
Subject: [PATCH v3 1/1] vfio-ccw: Prevent quiesce function going into an infinite loop
Date: Tue, 16 Apr 2019 17:23:14 -0400 [thread overview]
Message-ID: <4d5a4b98ab1b41ac6131b5c36de18b76c5d66898.1555449329.git.alifm@linux.ibm.com> (raw)
In-Reply-To: <cover.1555449329.git.alifm@linux.ibm.com>
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>
---
ChangeLog:
v2 -> v3
- Log an error message when cio_cancel_halt_clear
returns EIO and break out of the loop.
- Did not include past change log as the other patches
of the original series have been queued by Conny.
Old series (v2) can be found here:
https://marc.info/?l=kvm&m=155475754101769&w=2
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 78517aa..66a66ac 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:
--
2.7.4
next parent reply other threads:[~2019-04-16 21:23 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1555449329.git.alifm@linux.ibm.com>
2019-04-16 21:23 ` Farhan Ali [this message]
2019-04-17 9:03 ` [PATCH v3 1/1] vfio-ccw: Prevent quiesce function going into an infinite loop Cornelia Huck
2019-04-17 13:58 ` Eric Farman
2019-04-17 15:13 ` Halil Pasic
2019-04-17 15:18 ` Farhan Ali
2019-04-19 20:12 ` Halil Pasic
2019-04-22 14:01 ` Farhan Ali
2019-04-23 17:42 ` Halil Pasic
2019-04-23 19:41 ` Farhan Ali
2019-04-23 20:37 ` Eric Farman
2019-04-24 7:09 ` Cornelia Huck
2019-04-24 10:02 ` Halil Pasic
2019-04-24 10:21 ` Halil Pasic
2019-04-18 14:36 ` Cornelia Huck
2019-04-17 14:02 ` Farhan Ali
2019-04-24 16:35 ` Cornelia Huck
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