stm class: Mark src::link __rcu

Source device's link is protected with srcu, mark it as such to have
proper build-time validation of accesses to this field. The update
side that's dereferencing it under an update lock also needs an
accessor to dereference this field to keep sparse happy.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index b79c42c..b6445d9 100644 (file)
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -781,17 +781,20 @@ fail_detach:
 static void __stm_source_link_drop(struct stm_source_device *src,
                                   struct stm_device *stm)
 {
+       struct stm_device *link;
+
        spin_lock(&src->link_lock);
-       if (WARN_ON_ONCE(src->link != stm)) {
+       link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
+       if (WARN_ON_ONCE(link != stm)) {
                spin_unlock(&src->link_lock);
                return;
        }
 
-       stm_output_free(src->link, &src->output);
+       stm_output_free(link, &src->output);
        /* caller must hold stm::link_lock */
        list_del_init(&src->link_entry);
        /* matches stm_find_device() from stm_source_link_store() */
-       stm_put_device(src->link);
+       stm_put_device(link);
        rcu_assign_pointer(src->link, NULL);
 
        spin_unlock(&src->link_lock);

diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h
index cf33bf9..95ece02 100644 (file)
--- a/drivers/hwtracing/stm/stm.h
+++ b/drivers/hwtracing/stm/stm.h
@@ -74,7 +74,7 @@ struct stm_source_device {
        struct device           dev;
        struct stm_source_data  *data;
        spinlock_t              link_lock;
-       struct stm_device       *link;
+       struct stm_device __rcu *link;
        struct list_head        link_entry;
        /* one output per stm_source device */
        struct stp_policy_node  *policy_node;