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drm: Protect fb_helper list manipulation with a mutex

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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@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20161129120217.7344-3-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2016-11-29 12:02:17 +00:00 committed by Sean Paul
parent 64e94407fb
commit a53ca63502
1 changed files with 5 additions and 0 deletions
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5
drivers/gpu/drm/drm_fb_helper.c
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@ -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;
}