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From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/atomic: Acquire connection_mutex lock in drm_helper_probe_single_connector_modes.
Date: Wed, 29 Mar 2017 15:31:27 +0200	[thread overview]
Message-ID: <20170329153127.2a78d4e7@bbrezillon> (raw)
In-Reply-To: <20170329132645.w5j7gvizgrtkvxon@phenom.ffwll.local>

On Wed, 29 Mar 2017 15:26:45 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Wed, Mar 29, 2017 at 12:16:50PM +0200, Maarten Lankhorst wrote:
> > mode_valid() and get_modes() called
> > from drm_helper_probe_single_connector_modes()
> > may need to look at connector->state because what a valid mode is may
> > depend on connector properties being set. For example some HDMI modes
> > might be rejected when a connector property forces the connector
> > into DVI mode.
> > 
> > Some implementations of detect() already lock all state,
> > so we have to pass an acquire_ctx to them to prevent a deadlock.
> > 
> > This means changing the function signature of detect() slightly,
> > and passing the acquire_ctx for locking multiple crtc's.
> > It might be NULL, in which case expensive operations should be avoided.
> > 
> > intel_dp.c however ignores the force flag, so still lock
> > connection_mutex there if needed.
> > 
> > Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
> > Cc: Manasi Navare <manasi.d.navare@intel.com>  
> 
> Hm only noticed this now, but mixing up force with the acquire_ctx sounds
> like very bad interface design. Yes, the only user of the new hook works
> like that, but that's really accidental I think. I think just having the
> ctx everywhere (for atomic drivers at least) would be a lot safer. This is
> extremely surprising (and undocumented suprise at that).

Yes, I was about to say the same thing: the interface is not very
clear, and I don't understand why ctx = NULL implies force = false.
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  reply	other threads:[~2017-03-29 13:31 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-29 10:16 [PATCH] drm/atomic: Acquire connection_mutex lock in drm_helper_probe_single_connector_modes Maarten Lankhorst
2017-03-29 10:54 ` ✓ Fi.CI.BAT: success for " Patchwork
2017-03-29 13:26 ` [PATCH] " Daniel Vetter
2017-03-29 13:31   ` Boris Brezillon [this message]
2017-03-29 13:51     ` [Intel-gfx] " Maarten Lankhorst
2017-03-29 14:06       ` Daniel Vetter
2017-03-29 14:16         ` Maarten Lankhorst

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