Though we only walk the kernel_fb_helper_list inside a panic (or single thread debugging), we still need to protect the list manipulation on creating/removing a framebuffer device in order to prevent list corruption.
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch> --- drivers/gpu/drm/drm_fb_helper.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 90da28d2fcf3..e934b541feea 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -49,6 +49,7 @@ MODULE_PARM_DESC(fbdev_emulation, "Enable legacy fbdev emulation [default=true]"); static LIST_HEAD(kernel_fb_helper_list); +static DEFINE_MUTEX(kernel_fb_helper_lock); /** * DOC: fbdev helpers @@ -855,12 +856,14 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper) if (!drm_fbdev_emulation) return; + mutex_lock(&kernel_fb_helper_lock); if (!list_empty(&fb_helper->kernel_fb_list)) { list_del(&fb_helper->kernel_fb_list); if (list_empty(&kernel_fb_helper_list)) { unregister_sysrq_key('v', &sysrq_drm_fb_helper_restore_op); } } + mutex_unlock(&kernel_fb_helper_lock); drm_fb_helper_crtc_free(fb_helper); @@ -2258,10 +2261,12 @@ int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel) dev_info(dev->dev, "fb%d: %s frame buffer device\n", info->node, info->fix.id); + mutex_lock(&kernel_fb_helper_lock); if (list_empty(&kernel_fb_helper_list)) register_sysrq_key('v', &sysrq_drm_fb_helper_restore_op); list_add(&fb_helper->kernel_fb_list, &kernel_fb_helper_list); + mutex_unlock(&kernel_fb_helper_lock); return 0; } -- 2.10.2