drm/nouveau: Add a dedicated mutex for the clients list

Rather than protecting the nouveau_drm clients list with the lock within
the "client" nouveau_cli, add a dedicated lock to serialize access to
the list. This is both clearer and necessary to avoid lockdep being
upset with us when we need to iterate through all the clients in the
list and potentially lock their mutex, which is the same class as the
lock protecting the entire list.

Cc: stable@vger.kernel.org # 5.4+
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ben Skeggs <bskeggs@redhat.com>
Tested-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201125202648.5220-3-jcline@redhat.com
Link: https://gitlab.freedesktop.org/drm/nouveau/-/merge_requests/14

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 96490cc855cc993b30c12b0b263ade391a6ce469..4c69ac2a8295edbf2fc9657a8db2113d4accb18b 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -562,6 +562,7 @@ nouveau_drm_device_init(struct drm_device *dev)
                nvkm_dbgopt(nouveau_debug, "DRM");
 
        INIT_LIST_HEAD(&drm->clients);
+       mutex_init(&drm->clients_lock);
        spin_lock_init(&drm->tile.lock);
 
        /* workaround an odd issue on nvc1 by disabling the device's
@@ -659,6 +660,7 @@ nouveau_drm_device_fini(struct drm_device *dev)
        nouveau_cli_fini(&drm->client);
        nouveau_cli_fini(&drm->master);
        nvif_parent_dtor(&drm->parent);
+       mutex_destroy(&drm->clients_lock);
        kfree(drm);
 }
 
@@ -1090,9 +1092,9 @@ nouveau_drm_open(struct drm_device *dev, struct drm_file *fpriv)
 
        fpriv->driver_priv = cli;
 
-       mutex_lock(&drm->client.mutex);
+       mutex_lock(&drm->clients_lock);
        list_add(&cli->head, &drm->clients);
-       mutex_unlock(&drm->client.mutex);
+       mutex_unlock(&drm->clients_lock);
 
 done:
        if (ret && cli) {
@@ -1118,9 +1120,9 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv)
                nouveau_abi16_fini(cli->abi16);
        mutex_unlock(&cli->mutex);
 
-       mutex_lock(&drm->client.mutex);
+       mutex_lock(&drm->clients_lock);
        list_del(&cli->head);
-       mutex_unlock(&drm->client.mutex);
+       mutex_unlock(&drm->clients_lock);
 
        nouveau_cli_fini(cli);
        kfree(cli);

diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h
index ba65f136cf481d5c9d36656fa929be47a31bc5fb..b2a970aa9bf4b9dfc36a0da2e60f30b0b1e92114 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_drv.h
+++ b/drivers/gpu/drm/nouveau/nouveau_drv.h
@@ -139,6 +139,11 @@ struct nouveau_drm {
 
        struct list_head clients;
 
+       /**
+        * @clients_lock: Protects access to the @clients list of &struct nouveau_cli.
+        */
+       struct mutex clients_lock;
+
        u8 old_pm_cap;
 
        struct {