In order to be able to traverse the mostly read-only rproc_list without
locking during panic migrate traversal to be done under rcu_read_lock().
Mutual exclusion for modifications of the list continues to be handled
by the rproc_list_mutex and a synchronization point is added before
releasing objects that are popped from the list.
Reviewed-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---
Changes since v4:
- Added rculist include
- Picked up Mathieu's r-b
drivers/remoteproc/remoteproc_core.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index a9ac1d01e09b..7ee976ee2044 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -26,6 +26,7 @@
#include <linux/string.h>
#include <linux/debugfs.h>
#include <linux/devcoredump.h>
+#include <linux/rculist.h>
#include <linux/remoteproc.h>
#include <linux/iommu.h>
#include <linux/idr.h>
@@ -1868,8 +1869,8 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
if (!np)
return NULL;
- mutex_lock(&rproc_list_mutex);
- list_for_each_entry(r, &rproc_list, node) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(r, &rproc_list, node) {
if (r->dev.parent && r->dev.parent->of_node == np) {
/* prevent underlying implementation from being removed */
if (!try_module_get(r->dev.parent->driver->owner)) {
@@ -1882,7 +1883,7 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
break;
}
}
- mutex_unlock(&rproc_list_mutex);
+ rcu_read_unlock();
of_node_put(np);
@@ -1939,7 +1940,7 @@ int rproc_add(struct rproc *rproc)
/* expose to rproc_get_by_phandle users */
mutex_lock(&rproc_list_mutex);
- list_add(&rproc->node, &rproc_list);
+ list_add_rcu(&rproc->node, &rproc_list);
mutex_unlock(&rproc_list_mutex);
return 0;
@@ -2156,9 +2157,12 @@ int rproc_del(struct rproc *rproc)
/* the rproc is downref'ed as soon as it's removed from the klist */
mutex_lock(&rproc_list_mutex);
- list_del(&rproc->node);
+ list_del_rcu(&rproc->node);
mutex_unlock(&rproc_list_mutex);
+ /* Ensure that no readers of rproc_list are still active */
+ synchronize_rcu();
+
device_del(&rproc->dev);
return 0;
--
2.24.0
