From: Daniel Vetter <daniel.vetter@ffwll.ch> To: LKML <linux-kernel@vger.kernel.org> Cc: DRI Development <dri-devel@lists.freedesktop.org>, Intel Graphics Development <intel-gfx@lists.freedesktop.org>, linux-fbdev@vger.kernel.org, Daniel Thompson <daniel.thompson@linaro.org>, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>, Daniel Vetter <daniel.vetter@ffwll.ch>, Daniel Vetter <daniel.vetter@intel.com>, Sam Ravnborg <sam@ravnborg.org>, Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Hans de Goede <hdegoede@redhat.com>, Yisheng Xie <ysxie@foxmail.com> Subject: [PATCH 31/33] fbcon: Document what I learned about fbcon locking Date: Tue, 28 May 2019 11:03:02 +0200 [thread overview] Message-ID: <20190528090304.9388-32-daniel.vetter@ffwll.ch> (raw) In-Reply-To: <20190528090304.9388-1-daniel.vetter@ffwll.ch> It's not pretty. Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Reviewed-by: Sam Ravnborg <sam@ravnborg.org> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Hans de Goede <hdegoede@redhat.com> Cc: Yisheng Xie <ysxie@foxmail.com> --- drivers/video/fbdev/core/fbcon.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index fbd28aeff307..d6ba3610ee83 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -88,6 +88,25 @@ # define DPRINTK(fmt, args...) #endif +/* + * FIXME: Locking + * + * - fbcon state itself is protected by the console_lock, and the code does a + * pretty good job at making sure that lock is held everywhere it's needed. + * + * - access to the registered_fb array is entirely unprotected. This should use + * proper object lifetime handling, i.e. get/put_fb_info. This also means + * switching from indices to proper pointers for fb_info everywhere. + * + * - fbcon doesn't bother with fb_lock/unlock at all. This is buggy, since it + * means concurrent access to the same fbdev from both fbcon and userspace + * will blow up. To fix this all fbcon calls from fbmem.c need to be moved out + * of fb_lock/unlock protected sections, since otherwise we'll recurse and + * deadlock eventually. Aside: Due to these deadlock issues the fbdev code in + * fbmem.c cannot use locking asserts, and there's lots of callers which get + * the rules wrong, e.g. fbsysfs.c entirely missed fb_lock/unlock calls too. + */ + enum { FBCON_LOGO_CANSHOW = -1, /* the logo can be shown */ FBCON_LOGO_DRAW = -2, /* draw the logo to a console */ -- 2.20.1
WARNING: multiple messages have this Message-ID (diff)
From: Daniel Vetter <daniel.vetter@ffwll.ch> To: LKML <linux-kernel@vger.kernel.org> Cc: DRI Development <dri-devel@lists.freedesktop.org>, Intel Graphics Development <intel-gfx@lists.freedesktop.org>, linux-fbdev@vger.kernel.org, Daniel Thompson <daniel.thompson@linaro.org>, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>, Daniel Vetter <daniel.vetter@ffwll.ch>, Daniel Vetter <daniel.vetter@intel.com>, Sam Ravnborg <sam@ravnborg.org>, Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Hans de Goede <hdegoede@redhat.com>, Yisheng Xie <ysxie@foxmail.com> Subject: [PATCH 31/33] fbcon: Document what I learned about fbcon locking Date: Tue, 28 May 2019 09:03:02 +0000 [thread overview] Message-ID: <20190528090304.9388-32-daniel.vetter@ffwll.ch> (raw) In-Reply-To: <20190528090304.9388-1-daniel.vetter@ffwll.ch> It's not pretty. Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Reviewed-by: Sam Ravnborg <sam@ravnborg.org> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Hans de Goede <hdegoede@redhat.com> Cc: Yisheng Xie <ysxie@foxmail.com> --- drivers/video/fbdev/core/fbcon.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index fbd28aeff307..d6ba3610ee83 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -88,6 +88,25 @@ # define DPRINTK(fmt, args...) #endif +/* + * FIXME: Locking + * + * - fbcon state itself is protected by the console_lock, and the code does a + * pretty good job at making sure that lock is held everywhere it's needed. + * + * - access to the registered_fb array is entirely unprotected. This should use + * proper object lifetime handling, i.e. get/put_fb_info. This also means + * switching from indices to proper pointers for fb_info everywhere. + * + * - fbcon doesn't bother with fb_lock/unlock at all. This is buggy, since it + * means concurrent access to the same fbdev from both fbcon and userspace + * will blow up. To fix this all fbcon calls from fbmem.c need to be moved out + * of fb_lock/unlock protected sections, since otherwise we'll recurse and + * deadlock eventually. Aside: Due to these deadlock issues the fbdev code in + * fbmem.c cannot use locking asserts, and there's lots of callers which get + * the rules wrong, e.g. fbsysfs.c entirely missed fb_lock/unlock calls too. + */ + enum { FBCON_LOGO_CANSHOW = -1, /* the logo can be shown */ FBCON_LOGO_DRAW = -2, /* draw the logo to a console */ -- 2.20.1
next prev parent reply other threads:[~2019-05-28 9:04 UTC|newest] Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-05-28 9:02 [PATCH 00/33] fbcon notifier begone v3! Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 01/33] dummycon: Sprinkle locking checks Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 02/33] fbdev: locking check for fb_set_suspend Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 03/33] vt: might_sleep() annotation for do_blank_screen Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 04/33] vt: More locking checks Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 05/33] fbdev/sa1100fb: Remove dead code Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 06/33] fbdev/cyber2000: Remove struct display Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 07/33] fbdev/aty128fb: Remove dead code Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 08/33] fbcon: s/struct display/struct fbcon_display/ Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 09/33] fbcon: Remove fbcon_has_exited Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 10/33] fbcon: call fbcon_fb_(un)registered directly Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 11/33] fbdev/sh_mobile: remove sh_mobile_lcdc_display_notify Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 12/33] fbdev/omap: sysfs files can't disappear before the device is gone Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 13/33] fbdev: " Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 14/33] staging/olpc: lock_fb_info can't fail Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 15/33] fbdev/atyfb: " Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 16/33] fbdev: lock_fb_info cannot fail Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 17/33] fbcon: call fbcon_fb_bind directly Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 18/33] fbdev: make unregister/unlink functions not fail Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 19/33] fbdev: unify unlink_framebuffer paths Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 20/33] fbdev/sh_mob: Remove fb notifier callback Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 21/33] fbdev: directly call fbcon_suspended/resumed Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 22/33] fbcon: Call fbcon_mode_deleted/new_modelist directly Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 23/33] fbdev: Call fbcon_get_requirement directly Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 24/33] Revert "backlight/fbcon: Add FB_EVENT_CONBLANK" Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-06-11 14:09 ` Daniel Thompson 2019-06-11 14:09 ` Daniel Thompson 2019-06-11 14:09 ` Daniel Thompson 2019-06-11 15:39 ` Daniel Vetter 2019-06-11 15:39 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 25/33] fbmem: pull fbcon_fb_blanked out of fb_blank Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 26/33] fbdev: remove FBINFO_MISC_USEREVENT around fb_blank Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 27/33] fb: Flatten control flow in fb_set_var Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-05-28 9:02 ` [PATCH 28/33] fbcon: replace FB_EVENT_MODE_CHANGE/_ALL with direct calls Daniel Vetter 2019-05-28 9:02 ` Daniel Vetter 2019-06-11 14:11 ` Daniel Thompson 2019-06-11 14:11 ` Daniel Thompson 2019-06-11 14:11 ` Daniel Thompson 2019-05-28 9:03 ` [PATCH 29/33] vgaswitcheroo: call fbcon_remap_all directly Daniel Vetter 2019-05-28 9:03 ` Daniel Vetter 2019-05-28 9:03 ` [PATCH 30/33] fbcon: Call con2fb_map functions directly Daniel Vetter 2019-05-28 9:03 ` Daniel Vetter 2019-05-28 9:03 ` Daniel Vetter [this message] 2019-05-28 9:03 ` [PATCH 31/33] fbcon: Document what I learned about fbcon locking Daniel Vetter 2019-05-28 9:03 ` [PATCH 32/33] staging/olpc_dcon: Add drm conversion to TODO Daniel Vetter 2019-05-28 9:03 ` Daniel Vetter 2019-05-28 9:03 ` [PATCH 33/33] backlight: simplify lcd notifier Daniel Vetter 2019-05-28 9:03 ` Daniel Vetter 2019-06-11 14:11 ` Daniel Thompson 2019-06-11 14:11 ` Daniel Thompson 2019-06-11 14:11 ` Daniel Thompson 2019-05-28 12:22 ` ✗ Fi.CI.CHECKPATCH: warning for fbcon notifier begone v3! Patchwork 2019-05-28 12:36 ` ✗ Fi.CI.SPARSE: " Patchwork 2019-05-28 12:41 ` ✓ Fi.CI.BAT: success " Patchwork 2019-05-28 18:11 ` ✓ Fi.CI.IGT: " Patchwork 2019-06-06 7:38 ` [PATCH 00/33] " Daniel Vetter 2019-06-06 7:38 ` Daniel Vetter 2019-06-07 10:07 ` Bartlomiej Zolnierkiewicz 2019-06-07 10:07 ` Bartlomiej Zolnierkiewicz 2019-06-07 14:43 ` Daniel Vetter 2019-06-07 14:43 ` Daniel Vetter 2019-06-07 14:43 ` Daniel Vetter 2019-06-11 14:16 ` Daniel Thompson 2019-06-11 14:16 ` Daniel Thompson 2019-06-11 14:16 ` Daniel Thompson 2019-06-11 15:50 ` Daniel Vetter 2019-06-11 15:50 ` Daniel Vetter 2019-06-11 15:50 ` Daniel Vetter 2019-06-12 6:09 ` Lee Jones 2019-06-12 6:09 ` Lee Jones -- strict thread matches above, loose matches on Subject: below -- 2019-05-24 8:53 [PATCH 00/33] fbcon notifier begone! Daniel Vetter 2019-05-24 8:53 ` [PATCH 31/33] fbcon: Document what I learned about fbcon locking Daniel Vetter
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