diff options
| author | Farhan Ali <alifm@linux.ibm.com> | 2019-04-16 17:23:14 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-31 06:43:59 -0700 |
| commit | db08b2bf67a5510f79f2bbdafe7e7e791343b47b (patch) | |
| tree | 7743c6a96ec2565d1fd704e8a7a91e27f2bee7fa | |
| parent | 62431eed2f2514028ba600cb7142da519098d0b8 (diff) | |
vfio-ccw: Prevent quiesce function going into an infinite loop
[ 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>
| -rw-r--r-- | drivers/s390/cio/vfio_ccw_drv.c | 32 |
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 64bb121ba598..9e84d8a971ad 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -40,26 +40,30 @@ 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: |