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From: Sam Ravnborg <sam@ravnborg.org>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>,
	"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Michał Mirosław" <mirq-linux@rere.qmqm.pl>,
	"Hans de Goede" <hdegoede@redhat.com>,
	"Mikulas Patocka" <mpatocka@redhat.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Peter Rosin" <peda@axentia.se>
Subject: Re: [PATCH 25/33] fbmem: pull fbcon_fb_blanked out of fb_blank
Date: Sat, 25 May 2019 19:00:54 +0200	[thread overview]
Message-ID: <20190525170054.GA9076@ravnborg.org> (raw)
In-Reply-To: <20190524085354.27411-26-daniel.vetter@ffwll.ch>

Hi Daniel.

On Fri, May 24, 2019 at 10:53:46AM +0200, Daniel Vetter wrote:
> There's a callchain of:
> 
> fbcon_fb_blaned -> do_(un)blank_screen -> consw->con_blank
           ^^^^^^
Spelling error - as this is a callchain it would be good to have it
fixed.

Patch itself looks fine.

	Sam

> 	-> fbcon_blank -> fb_blank
> 
> Things don't go horribly wrong because the BKL console_lock safes the
> day, but that's about it. And the seeming recursion is broken in 2
> ways:
> - Starting from the fbdev ioctl we set FBINFO_MISC_USEREVENT, which
>   tells the fbcon_blank code to not call fb_blank. This was required
>   to not deadlock when recursing on the fb_notifier_chain mutex.
> - Starting from the con_blank hook we're getting saved by the
>   console_blanked checks in do_blank/unblank_screen. Or at least
>   that's my theory.
> 
> Anyway, recursion isn't awesome, so let's stop it. Breaking the
> recursion avoids the need to be in the FBINFO_MISC_USEREVENT critical
> section, so lets move it out of that too.
> 
> The astute reader will notice that fb_blank seems to require
> lock_fb_info(), which the fbcon code seems to ignore. I have no idea
> how to fix that problem, so let's keep ignoring it.
> 
> v2: I forgot the sysfs blanking code.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
> Cc: Peter Rosin <peda@axentia.se>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Mikulas Patocka <mpatocka@redhat.com>
> Cc: Rob Clark <robdclark@gmail.com>
> ---
>  drivers/video/fbdev/core/fbmem.c   | 4 +++-
>  drivers/video/fbdev/core/fbsysfs.c | 8 ++++++--
>  2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 9366fbe99a58..d6713dce9e31 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1068,7 +1068,6 @@ fb_blank(struct fb_info *info, int blank)
>  	event.data = &blank;
>  
>  	early_ret = fb_notifier_call_chain(FB_EARLY_EVENT_BLANK, &event);
> -	fbcon_fb_blanked(info, blank);
>  
>  	if (info->fbops->fb_blank)
>   		ret = info->fbops->fb_blank(blank, info);
> @@ -1198,6 +1197,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
>  		info->flags |= FBINFO_MISC_USEREVENT;
>  		ret = fb_blank(info, arg);
>  		info->flags &= ~FBINFO_MISC_USEREVENT;
> +
> +		/* might again call into fb_blank */
> +		fbcon_fb_blanked(info, arg);
>  		unlock_fb_info(info);
>  		console_unlock();
>  		break;
> diff --git a/drivers/video/fbdev/core/fbsysfs.c b/drivers/video/fbdev/core/fbsysfs.c
> index 5f329278e55f..252d4f52d2a5 100644
> --- a/drivers/video/fbdev/core/fbsysfs.c
> +++ b/drivers/video/fbdev/core/fbsysfs.c
> @@ -18,6 +18,7 @@
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/fb.h>
> +#include <linux/fbcon.h>
>  #include <linux/console.h>
>  #include <linux/module.h>
>  
> @@ -305,12 +306,15 @@ static ssize_t store_blank(struct device *device,
>  {
>  	struct fb_info *fb_info = dev_get_drvdata(device);
>  	char *last = NULL;
> -	int err;
> +	int err, arg;
>  
> +	arg = simple_strtoul(buf, &last, 0);
>  	console_lock();
>  	fb_info->flags |= FBINFO_MISC_USEREVENT;
> -	err = fb_blank(fb_info, simple_strtoul(buf, &last, 0));
> +	err = fb_blank(fb_info, arg);
>  	fb_info->flags &= ~FBINFO_MISC_USEREVENT;
> +	/* might again call into fb_blank */
> +	fbcon_fb_blanked(fb_info, arg);
>  	console_unlock();
>  	if (err < 0)
>  		return err;
> -- 
> 2.20.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

WARNING: multiple messages have this Message-ID
From: Sam Ravnborg <sam@ravnborg.org>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>,
	"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Michał Mirosław" <mirq-linux@rere.qmqm.pl>,
	"Mikulas Patocka" <mpatocka@redhat.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Peter Rosin" <peda@axentia.se>
Subject: Re: [PATCH 25/33] fbmem: pull fbcon_fb_blanked out of fb_blank
Date: Sat, 25 May 2019 19:00:54 +0200	[thread overview]
Message-ID: <20190525170054.GA9076@ravnborg.org> (raw)
In-Reply-To: <20190524085354.27411-26-daniel.vetter@ffwll.ch>

Hi Daniel.

On Fri, May 24, 2019 at 10:53:46AM +0200, Daniel Vetter wrote:
> There's a callchain of:
> 
> fbcon_fb_blaned -> do_(un)blank_screen -> consw->con_blank
           ^^^^^^
Spelling error - as this is a callchain it would be good to have it
fixed.

Patch itself looks fine.

	Sam

> 	-> fbcon_blank -> fb_blank
> 
> Things don't go horribly wrong because the BKL console_lock safes the
> day, but that's about it. And the seeming recursion is broken in 2
> ways:
> - Starting from the fbdev ioctl we set FBINFO_MISC_USEREVENT, which
>   tells the fbcon_blank code to not call fb_blank. This was required
>   to not deadlock when recursing on the fb_notifier_chain mutex.
> - Starting from the con_blank hook we're getting saved by the
>   console_blanked checks in do_blank/unblank_screen. Or at least
>   that's my theory.
> 
> Anyway, recursion isn't awesome, so let's stop it. Breaking the
> recursion avoids the need to be in the FBINFO_MISC_USEREVENT critical
> section, so lets move it out of that too.
> 
> The astute reader will notice that fb_blank seems to require
> lock_fb_info(), which the fbcon code seems to ignore. I have no idea
> how to fix that problem, so let's keep ignoring it.
> 
> v2: I forgot the sysfs blanking code.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
> Cc: Peter Rosin <peda@axentia.se>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Mikulas Patocka <mpatocka@redhat.com>
> Cc: Rob Clark <robdclark@gmail.com>
> ---
>  drivers/video/fbdev/core/fbmem.c   | 4 +++-
>  drivers/video/fbdev/core/fbsysfs.c | 8 ++++++--
>  2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 9366fbe99a58..d6713dce9e31 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1068,7 +1068,6 @@ fb_blank(struct fb_info *info, int blank)
>  	event.data = &blank;
>  
>  	early_ret = fb_notifier_call_chain(FB_EARLY_EVENT_BLANK, &event);
> -	fbcon_fb_blanked(info, blank);
>  
>  	if (info->fbops->fb_blank)
>   		ret = info->fbops->fb_blank(blank, info);
> @@ -1198,6 +1197,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
>  		info->flags |= FBINFO_MISC_USEREVENT;
>  		ret = fb_blank(info, arg);
>  		info->flags &= ~FBINFO_MISC_USEREVENT;
> +
> +		/* might again call into fb_blank */
> +		fbcon_fb_blanked(info, arg);
>  		unlock_fb_info(info);
>  		console_unlock();
>  		break;
> diff --git a/drivers/video/fbdev/core/fbsysfs.c b/drivers/video/fbdev/core/fbsysfs.c
> index 5f329278e55f..252d4f52d2a5 100644
> --- a/drivers/video/fbdev/core/fbsysfs.c
> +++ b/drivers/video/fbdev/core/fbsysfs.c
> @@ -18,6 +18,7 @@
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/fb.h>
> +#include <linux/fbcon.h>
>  #include <linux/console.h>
>  #include <linux/module.h>
>  
> @@ -305,12 +306,15 @@ static ssize_t store_blank(struct device *device,
>  {
>  	struct fb_info *fb_info = dev_get_drvdata(device);
>  	char *last = NULL;
> -	int err;
> +	int err, arg;
>  
> +	arg = simple_strtoul(buf, &last, 0);
>  	console_lock();
>  	fb_info->flags |= FBINFO_MISC_USEREVENT;
> -	err = fb_blank(fb_info, simple_strtoul(buf, &last, 0));
> +	err = fb_blank(fb_info, arg);
>  	fb_info->flags &= ~FBINFO_MISC_USEREVENT;
> +	/* might again call into fb_blank */
> +	fbcon_fb_blanked(fb_info, arg);
>  	console_unlock();
>  	if (err < 0)
>  		return err;
> -- 
> 2.20.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2019-05-25 17:01 UTC|newest]

Thread overview: 103+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-24  8:53 [PATCH 00/33] fbcon notifier begone! Daniel Vetter
2019-05-24  8:53 ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 01/33] dummycon: Sprinkle locking checks Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 02/33] fbdev: locking check for fb_set_suspend Daniel Vetter
2019-05-24  8:53 ` [PATCH 03/33] vt: might_sleep() annotation for do_blank_screen Daniel Vetter
2019-05-24  8:53 ` [PATCH 04/33] vt: More locking checks Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-27  7:08   ` Daniel Vetter
2019-05-27  7:08     ` Daniel Vetter
2019-05-27  7:22     ` Greg Kroah-Hartman
2019-05-24  8:53 ` [PATCH 05/33] fbdev/sa1100fb: Remove dead code Daniel Vetter
2019-05-24  8:53 ` [PATCH 06/33] fbdev/cyber2000: Remove struct display Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 07/33] fbdev/aty128fb: Remove dead code Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 08/33] fbcon: s/struct display/struct fbcon_display/ Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 09/33] fbcon: Remove fbcon_has_exited Daniel Vetter
2019-05-25 15:38   ` Sam Ravnborg
2019-05-25 15:38     ` Sam Ravnborg
2019-05-27  6:10     ` Daniel Vetter
2019-05-27  6:10       ` Daniel Vetter
2019-05-27  6:51       ` Sam Ravnborg
2019-05-27  6:51         ` Sam Ravnborg
2019-05-24  8:53 ` [PATCH 10/33] fbcon: call fbcon_fb_(un)registered directly Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 11/33] fbdev/sh_mobile: remove sh_mobile_lcdc_display_notify Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-25 15:01   ` Sam Ravnborg
2019-05-25 15:01     ` Sam Ravnborg
2019-05-27  6:13     ` Daniel Vetter
2019-05-27  6:52       ` Sam Ravnborg
2019-05-24  8:53 ` [PATCH 12/33] fbdev/omap: sysfs files can't disappear before the device is gone Daniel Vetter
2019-05-24  8:53 ` [PATCH 13/33] fbdev: " Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 14/33] staging/olpc: lock_fb_info can't fail Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-27  7:10   ` Daniel Vetter
2019-05-27  7:22     ` Greg KH
2019-05-27  7:22       ` Greg KH
2019-05-24  8:53 ` [PATCH 15/33] fbdev/atyfb: " Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 16/33] fbdev: lock_fb_info cannot fail Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 17/33] fbcon: call fbcon_fb_bind directly Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 18/33] fbdev: make unregister/unlink functions not fail Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 19/33] fbdev: unify unlink_framebuffer paths Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 20/33] fbdev/sh_mob: Remove fb notifier callback Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 21/33] fbdev: directly call fbcon_suspended/resumed Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 22/33] fbcon: Call fbcon_mode_deleted/new_modelist directly Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 23/33] fbdev: Call fbcon_get_requirement directly Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 24/33] Revert "backlight/fbcon: Add FB_EVENT_CONBLANK" Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24 13:14   ` Daniel Thompson
2019-05-24 13:14     ` Daniel Thompson
2019-05-24 13:14     ` Daniel Thompson
2019-05-24 15:28     ` Daniel Vetter
2019-05-24 15:28       ` Daniel Vetter
2019-05-27 10:59       ` Bartlomiej Zolnierkiewicz
2019-05-27 10:59         ` Bartlomiej Zolnierkiewicz
2019-05-24  8:53 ` [PATCH 25/33] fbmem: pull fbcon_fb_blanked out of fb_blank Daniel Vetter
2019-05-25 17:00   ` Sam Ravnborg [this message]
2019-05-25 17:00     ` Sam Ravnborg
2019-05-24  8:53 ` [PATCH 26/33] fbdev: remove FBINFO_MISC_USEREVENT around fb_blank Daniel Vetter
2019-05-24  8:53 ` [PATCH 27/33] fb: Flatten control flow in fb_set_var Daniel Vetter
2019-05-24  8:53 ` [PATCH 28/33] fbcon: replace FB_EVENT_MODE_CHANGE/_ALL with direct calls Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 29/33] vgaswitcheroo: call fbcon_remap_all directly Daniel Vetter
2019-05-24  8:53   ` Daniel Vetter
2019-05-24  8:53 ` [PATCH 30/33] fbcon: Call con2fb_map functions directly Daniel Vetter
2019-05-24  8:53 ` [PATCH 31/33] fbcon: Document what I learned about fbcon locking Daniel Vetter
2019-05-24  8:53 ` [PATCH 32/33] staging/olpc_dcon: Add drm conversion to TODO Daniel Vetter
2019-05-27  7:11   ` Daniel Vetter
2019-05-27  7:11     ` Daniel Vetter
2019-05-27  7:22     ` Greg KH
2019-05-24  8:53 ` [PATCH 33/33] backlight: simplify lcd notifier Daniel Vetter
2019-05-24 11:03 ` ✗ Fi.CI.CHECKPATCH: warning for fbcon notifier begone! (rev3) Patchwork
2019-05-24 11:18 ` ✗ Fi.CI.SPARSE: " Patchwork
2019-05-24 11:23 ` ✓ Fi.CI.BAT: success " Patchwork
2019-05-25 17:19 ` [PATCH 00/33] fbcon notifier begone! Sam Ravnborg
2019-05-27  7:17   ` Daniel Vetter
2019-05-27 11:56     ` Daniel Vetter
2019-05-25 17:24 ` ✗ Fi.CI.IGT: failure for fbcon notifier begone! (rev3) Patchwork
2019-05-26 15:34 ` ✗ Fi.CI.CHECKPATCH: warning for fbcon notifier begone! (rev4) Patchwork
2019-05-26 15:49 ` ✗ Fi.CI.SPARSE: " Patchwork
2019-05-26 15:53 ` ✓ Fi.CI.BAT: success " Patchwork
2019-05-27 11:02 ` ✓ Fi.CI.IGT: " Patchwork
2019-05-28  9:02 [PATCH 00/33] fbcon notifier begone v3! 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

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