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

commit abae9164a421bc4a41a3769f01ebcd1f9d955e0e upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 6109cd9e339918f5798787aad76cd3f1e69961f6..a420320439f260dc7d266b05b3f7d354584a970c 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 {