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From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	DRI Development <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 00/33] fbcon notifier begone!
Date: Mon, 27 May 2019 13:56:48 +0200	[thread overview]
Message-ID: <CAKMK7uEikzt0VRk-9nAScw1ppoOUs4Ay_L4KqHRD5FJBJAWmMQ@mail.gmail.com> (raw)
In-Reply-To: <20190527071729.GM21222@phenom.ffwll.local>

On Mon, May 27, 2019 at 9:17 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Sat, May 25, 2019 at 07:19:28PM +0200, Sam Ravnborg wrote:
> > Hi Daniel.
> >
> > Good work, nice cleanup all over.
> >
> > A few comments to a few patches - not something that warrant a
> > new series to be posted as long as it is fixed before the patches are
> > applied.
>
> Hm yeah good idea, I'll add that to the next version.

Actually I thought a bit more about the locking story, and it's a bit
worse than my simple plan here. I think better to just have that
floating around, and not make it look like it's an easy simple
cleanup.

The case I forgot about is that any places that has a printk can
recurse through the console_lock, which means we need a lot more
try_lock than I originally thought we'd need.
-Daniel

>
> > > btw for future plans: I think this is tricky enough (it's old code and all
> > > that) that we should let this soak for 2-3 kernel releases. I think the
> > > following would be nice subsequent cleanup/fixes:
> > >
> > > - push the console lock completely from fbmem.c to fbcon.c. I think we're
> > >   mostly there with prep, but needs to pondering of corner cases.
> > I wonder - should this code consistently use __acquire() etc so we could
> > get a little static analysis help for the locking?
> >
> > I have not played with this for several years and I do not know the
> > maturity of this today.
>
> Ime these sparse annotations are pretty useless because too inflexible. I
> tend to use runtime locking checks based on lockdep. Those are more
> accurate, and work even when the place the lock is taken is very far away
> from where you're checking, without having to annoate all functions in
> between. We need that for something like console_lock which is a very big
> lock. Only downside is that only paths you hit at runtime are checked.
>
> > > - move fbcon.c from using indices for tracking fb_info (and accessing
> > >   registered_fbs without proper locking all the time) to real fb_info
> > >   pointers with the right amount of refcounting. Mostly motivated by the
> > >   fun I had trying to simplify fbcon_exit().
> > >
> > > - make sure that fbcon call lock/unlock_fb when it calls fbmem.c
> > >   functions, and sprinkle assert_lockdep_held around in fbmem.c. This
> > >   needs the console_lock cleanups first.
> > >
> > > But I think that's material for maybe next year or so.
> > Or maybe after next kernel release.
> > Could we put this nice plan into todo.rst or similar so we do not have
> > to hunt it down by asking google?
> >
> > For the whole series you can add my:
> > Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> >
> > Some parts are reviewed as "this looks entirely correct", other parts
> > I would claim that I actually understood.
> > And after having spend some hours on this a r-b seems in order.
>
> Thanks, Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

  reply	other threads:[~2019-05-27 11:57 UTC|newest]

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-24  8:53 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
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 [this message]
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
  -- strict thread matches above, loose matches on Subject: below --
2019-05-20  8:21 [PATCH 00/33] fbcon notifier begone! Daniel Vetter

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