From: Peter Zijlstra <peterz@infradead.org>
To: Stefan Agner <stefan@agner.ch>
Cc: broonie@kernel.org, festevam@gmail.com, mingo@redhat.com,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: Lockdep warning when using REGCACHE_RBTREE
Date: Fri, 15 Jan 2016 10:45:41 +0100 [thread overview]
Message-ID: <20160115094541.GH3421@worktop> (raw)
In-Reply-To: <afeb9e00e3082de585cfa458a0f47c56@agner.ch>
On Thu, Jan 14, 2016 at 02:30:50PM -0800, Stefan Agner wrote:
> Hi Mark,
>
> I currently work on the DCU DRM driver (drivers/gpu/drm/fsl-dcu/) on a
> Linux 4.4 kernel. With CONFIG_LOCKDEP enabled I get the following
> warning on startup:
>
> [ 1.327284] ------------[ cut here ]------------
> [ 1.332010] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0x120/0x124()
> [ 1.341358] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
> [ 1.521744] [<80375308>] (_regmap_write) from [<80376760>] (regmap_write+0x48/0x68)
> [ 1.535348] [<80376718>] (regmap_write) from [<803538e8>] (fsl_dcu_drm_crtc_create+0x98/0xe8)
> [ 1.549824] [<80353850>] (fsl_dcu_drm_crtc_create) from [<80352df0>] (fsl_dcu_drm_modeset_init+0x5c/0xfc)
> The comment in __lockdep_trace_alloc says:
> "Oi! Can't be having __GFP_FS allocations with IRQs disabled.".
So _regmap_write() does: map->lock(map->lock_arg)
Which isn't very enlightening, since that can be a mutex or a spinlock,
the above strongly suggests spinlock though.
Looking at __regmap_init(), this seems to depend on:
(bus && bus->fast_io) || config->fast_io
now, afaict, regmap_mmio is used in this case, which has .fast_io =
true.
So yeah, fail.
next prev parent reply other threads:[~2016-01-15 9:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 22:30 Lockdep warning when using REGCACHE_RBTREE Stefan Agner
2016-01-15 0:01 ` Mark Brown
2016-01-15 1:14 ` Stefan Agner
2016-01-15 16:28 ` Mark Brown
2016-01-15 19:08 ` Stefan Agner
2016-01-15 9:45 ` Peter Zijlstra [this message]
2016-01-15 11:49 ` Mark Brown
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