From 5ef1dc40ffa6a6cb968b0fdc43c3a61727a9e950 Mon Sep 17 00:00:00 2001 From: Peter Oberparleiter Date: Wed, 14 Feb 2024 16:06:28 +0100 Subject: s390/cio: fix invalid -EBUSY on ccw_device_start The s390 common I/O layer (CIO) returns an unexpected -EBUSY return code when drivers try to start I/O while a path-verification (PV) process is pending. This can lead to failed device initialization attempts with symptoms like broken network connectivity after boot. Fix this by replacing the -EBUSY return code with a deferred condition code 1 reply to make path-verification handling consistent from a driver's point of view. The problem can be reproduced semi-regularly using the following process, while repeating steps 2-3 as necessary (example assumes an OSA device with bus-IDs 0.0.a000-0.0.a002 on CHPID 0.02): 1. echo 0.0.a000,0.0.a001,0.0.a002 >/sys/bus/ccwgroup/drivers/qeth/group 2. echo 0 > /sys/bus/ccwgroup/devices/0.0.a000/online 3. echo 1 > /sys/bus/ccwgroup/devices/0.0.a000/online ; \ echo on > /sys/devices/css0/chp0.02/status Background information: The common I/O layer starts path-verification I/Os when it receives indications about changes in a device path's availability. This occurs for example when hardware events indicate a change in channel-path status, or when a manual operation such as a CHPID vary or configure operation is performed. If a driver attempts to start I/O while a PV is running, CIO reports a successful I/O start (ccw_device_start() return code 0). Then, after completion of PV, CIO synthesizes an interrupt response that indicates an asynchronous status condition that prevented the start of the I/O (deferred condition code 1). If a PV indication arrives while a device is busy with driver-owned I/O, PV is delayed until after I/O completion was reported to the driver's interrupt handler. To ensure that PV can be started eventually, CIO reports a device busy condition (ccw_device_start() return code -EBUSY) if a driver tries to start another I/O while PV is pending. In some cases this -EBUSY return code causes device drivers to consider a device not operational, resulting in failed device initialization. Note: The code that introduced the problem was added in 2003. Symptoms started appearing with the following CIO commit that causes a PV indication when a device is removed from the cio_ignore list after the associated parent subchannel device was probed, but before online processing of the CCW device has started: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers") During boot, the cio_ignore list is modified by the cio_ignore dracut module [1] as well as Linux vendor-specific systemd service scripts[2]. When combined, this commit and boot scripts cause a frequent occurrence of the problem during boot. [1] https://github.com/dracutdevs/dracut/tree/master/modules.d/81cio_ignore [2] https://github.com/SUSE/s390-tools/blob/master/cio_ignore.service Cc: stable@vger.kernel.org # v5.15+ Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers") Tested-By: Thorsten Winkler Reviewed-by: Thorsten Winkler Signed-off-by: Peter Oberparleiter Signed-off-by: Heiko Carstens --- drivers/s390/cio/device_ops.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/s390') diff --git a/drivers/s390/cio/device_ops.c b/drivers/s390/cio/device_ops.c index c533d1dadc6b..a5dba3829769 100644 --- a/drivers/s390/cio/device_ops.c +++ b/drivers/s390/cio/device_ops.c @@ -202,7 +202,8 @@ int ccw_device_start_timeout_key(struct ccw_device *cdev, struct ccw1 *cpa, return -EINVAL; if (cdev->private->state == DEV_STATE_NOT_OPER) return -ENODEV; - if (cdev->private->state == DEV_STATE_VERIFY) { + if (cdev->private->state == DEV_STATE_VERIFY || + cdev->private->flags.doverify) { /* Remember to fake irb when finished. */ if (!cdev->private->flags.fake_irb) { cdev->private->flags.fake_irb = FAKE_CMD_IRB; @@ -214,8 +215,7 @@ int ccw_device_start_timeout_key(struct ccw_device *cdev, struct ccw1 *cpa, } if (cdev->private->state != DEV_STATE_ONLINE || ((sch->schib.scsw.cmd.stctl & SCSW_STCTL_PRIM_STATUS) && - !(sch->schib.scsw.cmd.stctl & SCSW_STCTL_SEC_STATUS)) || - cdev->private->flags.doverify) + !(sch->schib.scsw.cmd.stctl & SCSW_STCTL_SEC_STATUS))) return -EBUSY; ret = cio_set_options (sch, flags); if (ret) -- cgit v1.2.3