From: Eric Farman <farman@linux.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: Jared Rossi <jrossi@linux.ibm.com>,
Halil Pasic <pasic@linux.ibm.com>,
linux-s390@vger.kernel.org, kvm@vger.kernel.org,
Eric Farman <farman@linux.ibm.com>
Subject: [RFC PATCH v3 3/3] vfio-ccw: Check workqueue before doing START
Date: Tue, 16 Jun 2020 21:50:53 +0200 [thread overview]
Message-ID: <20200616195053.99253-4-farman@linux.ibm.com> (raw)
In-Reply-To: <20200616195053.99253-1-farman@linux.ibm.com>
When an interrupt is received via the IRQ, the bulk of the work is
stacked on a workqueue for later processing. Which means that concurrent
START or a HALT/CLEAR operation (via the async_region) will race with
this process and require some serialization.
Once we have all our locks acquired, let's just look to see if we're
in a window where the process has been started from the IRQ, but not
yet picked up by vfio-ccw to clean up an I/O. If there is, mark the
request as BUSY so it can be redriven after we have a chance to breathe.
Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
drivers/s390/cio/vfio_ccw_fsm.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index f0952192480e..9dc5b4d549b3 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -28,6 +28,11 @@ static int fsm_io_helper(struct vfio_ccw_private *private)
spin_lock_irqsave(sch->lock, flags);
+ if (work_pending(&private->io_work)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
orb = cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm);
if (!orb) {
ret = -EIO;
--
2.17.1
next prev parent reply other threads:[~2020-06-16 19:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-16 19:50 [RFC PATCH v3 0/3] vfio-ccw: Fix interrupt handling for HALT/CLEAR Eric Farman
2020-06-16 19:50 ` [RFC PATCH v3 1/3] vfio-ccw: Indicate if a channel_program is started Eric Farman
2020-06-17 23:11 ` Halil Pasic
2020-06-18 11:47 ` Eric Farman
2020-06-16 19:50 ` [RFC PATCH v3 2/3] vfio-ccw: Remove the CP_PENDING FSM state Eric Farman
2020-06-16 19:50 ` Eric Farman [this message]
2020-06-19 11:40 ` [RFC PATCH v3 3/3] vfio-ccw: Check workqueue before doing START Cornelia Huck
2020-06-17 11:24 ` [RFC PATCH v3 0/3] vfio-ccw: Fix interrupt handling for HALT/CLEAR Eric Farman
2020-06-29 14:56 ` Cornelia Huck
2020-06-30 19:10 ` Eric Farman
2020-06-19 11:21 ` Cornelia Huck
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