remoteproc: implement synchronize_cbs() for virtio devices

Platform drivers invoke rproc_vq_interrupt() from hard-IRQ handlers,
threaded handlers, and work items. Because rpmsg callbacks may sleep,
the virtio core's synchronize_rcu() fallback does not synchronize with
callbacks across all these contexts. A device reset can therefore
complete while a callback is still running.

Add an SRCU domain per rproc. Protect both the queue lookup and
vring_interrupt() with it, and synchronize the domain in the new hook.

__rproc_virtio_del_vqs() can race with rproc_vq_interrupt() too. Clear
all queue pointers and synchronize the SRCU domain before freeing the
queues, so callers that already found a queue can finish using it.
Read rvring->vq once to avoid a second load after deletion starts.

The SRCU domain has the same lifetime as struct rproc. Its cleanup can
sleep, so document that rproc_free() and rproc_put() must not drop the
last reference from atomic context.

Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260908053817.26065-4-kmehltretter@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
index a44368737b39..ff0ad1e12c01 100644
--- a/include/linux/remoteproc.h
+++ b/include/linux/remoteproc.h
@@ -15,6 +15,7 @@
 #include <linux/cdev.h>
 #include <linux/completion.h>
 #include <linux/idr.h>
+#include <linux/srcu.h>
 #include <linux/of.h>
 #include <linux/rsc_table.h>
 
@@ -228,6 +229,7 @@ enum rproc_features {
  * @mappings: list of iommu mappings we initiated, needed on shutdown
  * @bootaddr: address of first instruction to boot rproc with (optional)
  * @rvdevs: list of remote virtio devices
+ * @vq_srcu: SRCU domain for the virtqueue callbacks of @rvdevs
  * @subdevs: list of subdevices, to following the running state
  * @notifyids: idr for dynamically assigning rproc-wide unique notify ids
  * @index: index of this rproc device
@@ -274,6 +276,7 @@ struct rproc {
 	struct list_head mappings;
 	u64 bootaddr;
 	struct list_head rvdevs;
+	struct srcu_struct vq_srcu;
 	struct list_head subdevs;
 	struct idr notifyids;
 	int index;