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authorOhad Ben-Cohen <ohad@wizery.com>2012-06-06 10:09:25 +0300
committerOhad Ben-Cohen <ohad@wizery.com>2012-07-04 11:51:42 +0300
commit5a081caa0414b9bbb82c17ffab9d6fe66edbb72f (patch)
treede3c3d2044db5843e836690732a4f688985e35af /drivers/rpmsg
parent6887a4131da3adaab011613776d865f4bcfb5678 (diff)
downloadlinux-linaro-stable-5a081caa0414b9bbb82c17ffab9d6fe66edbb72f.tar.gz
rpmsg: avoid premature deallocation of endpoints
When an inbound message arrives, the rpmsg core looks up its associated endpoint and invokes the registered callback. If a message arrives while its endpoint is being removed (because the rpmsg driver was removed, or a recovery of a remote processor has kicked in) we must ensure atomicity, i.e.: - Either the ept is removed before it is found or - The ept is found but will not be freed until the callback returns This is achieved by maintaining a per-ept reference count, which, when drops to zero, will trigger deallocation of the ept. With this in hand, it is now forbidden to directly deallocate epts once they have been added to the endpoints idr. Cc: stable <stable@vger.kernel.org> Reported-by: Fernando Guzman Lugo <fernando.lugo@ti.com> Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Diffstat (limited to 'drivers/rpmsg')
-rw-r--r--drivers/rpmsg/virtio_rpmsg_bus.c36
1 files changed, 34 insertions, 2 deletions
diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 75506ec2840e..9623327ba509 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -188,6 +188,26 @@ static int rpmsg_uevent(struct device *dev, struct kobj_uevent_env *env)
rpdev->id.name);
}
+/**
+ * __ept_release() - deallocate an rpmsg endpoint
+ * @kref: the ept's reference count
+ *
+ * This function deallocates an ept, and is invoked when its @kref refcount
+ * drops to zero.
+ *
+ * Never invoke this function directly!
+ */
+static void __ept_release(struct kref *kref)
+{
+ struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
+ refcount);
+ /*
+ * At this point no one holds a reference to ept anymore,
+ * so we can directly free it
+ */
+ kfree(ept);
+}
+
/* for more info, see below documentation of rpmsg_create_ept() */
static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
struct rpmsg_channel *rpdev, rpmsg_rx_cb_t cb,
@@ -206,6 +226,8 @@ static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
return NULL;
}
+ kref_init(&ept->refcount);
+
ept->rpdev = rpdev;
ept->cb = cb;
ept->priv = priv;
@@ -238,7 +260,7 @@ rem_idr:
idr_remove(&vrp->endpoints, request);
free_ept:
mutex_unlock(&vrp->endpoints_lock);
- kfree(ept);
+ kref_put(&ept->refcount, __ept_release);
return NULL;
}
@@ -306,7 +328,7 @@ __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
idr_remove(&vrp->endpoints, ept->addr);
mutex_unlock(&vrp->endpoints_lock);
- kfree(ept);
+ kref_put(&ept->refcount, __ept_release);
}
/**
@@ -790,7 +812,13 @@ static void rpmsg_recv_done(struct virtqueue *rvq)
/* use the dst addr to fetch the callback of the appropriate user */
mutex_lock(&vrp->endpoints_lock);
+
ept = idr_find(&vrp->endpoints, msg->dst);
+
+ /* let's make sure no one deallocates ept while we use it */
+ if (ept)
+ kref_get(&ept->refcount);
+
mutex_unlock(&vrp->endpoints_lock);
if (ept && ept->cb)
@@ -798,6 +826,10 @@ static void rpmsg_recv_done(struct virtqueue *rvq)
else
dev_warn(dev, "msg received with no recepient\n");
+ /* farewell, ept, we don't need you anymore */
+ if (ept)
+ kref_put(&ept->refcount, __ept_release);
+
/* publish the real size of the buffer */
sg_init_one(&sg, msg, RPMSG_BUF_SIZE);