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remoteproc: Traverse rproc_list under RCU read lock 

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@linaro.org>
Link: https://lore.kernel.org/r/20200324052904.738594-2-bjorn.andersson@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
This commit is contained in:
Bjorn Andersson 2020-03-23 22:29:01 -07:00
parent 791c13b709
commit c0abe2ca36
1 changed files with 9 additions and 5 deletions
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14
drivers/remoteproc/remoteproc_core.c
View File

@ -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;