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From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Stein <alexander.stein@systec-electronic.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 2/2] arm: perf: Mark as non-removable
Date: Wed, 4 Jan 2017 11:40:56 +0000	[thread overview]
Message-ID: <20170104114056.GO14217@n2100.armlinux.org.uk> (raw)
In-Reply-To: <20170104113025.GE8329@leverpostej>

On Wed, Jan 04, 2017 at 11:30:25AM +0000, Mark Rutland wrote:
> On Wed, Jan 04, 2017 at 10:19:46AM +0100, Alexander Stein wrote:
> > I'm not sure if the change above works with remove functions set in struct 
> > bus_type too.
> > But on the other hand this would hide errors in drivers which are actually 
> > removable but do not cleanup properly which DEBUG_TEST_DRIVER_REMOVE tries to 
> > detect.
> > By setting .suppress_bind_attrs = true explicitely you state "This 
> > driver cannot be removed!", so the remove callback is not missing by accident.
> 
> I'm not sure I follow. If the remove callback is accidentally missing,
> the driver is not "actually removable" today -- there's either no remove
> code, or it's not been wired up (the latter of which will likely result
> in a compiler warning about an unused function).
> 
> Aborting the remove early in those cases is much safer than forcefully
> removing a driver without a remove callback.

Drivers without a remove function may be removable - there's more layers
than just the driver - there's the bus layer as well, which may or may
not direct to a private-bus pointer.

There's no real way for the core driver model code to know whether the
lack of the ->remove in the struct device_driver is something that
prevents a driver being removed, or whether it's handled via some other
method.  Eg, platform drivers.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

  reply	other threads:[~2017-01-04 11:41 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-21 15:03 [PATCH v2 0/2] mark driver " Alexander Stein
2016-12-21 15:03 ` [PATCH v2 1/2] drivers/perf: arm_pmu: Use devm_ allocators Alexander Stein
2016-12-21 15:03 ` [PATCH v2 2/2] arm: perf: Mark as non-removable Alexander Stein
2016-12-22 22:48   ` Mark Rutland
2017-01-04  9:19     ` Alexander Stein
2017-01-04 11:30       ` Mark Rutland
2017-01-04 11:40         ` Russell King - ARM Linux [this message]
2017-01-04 11:46           ` Mark Rutland
2017-01-04 18:17             ` Will Deacon
2016-12-21 23:17 ` [PATCH v2 0/2] mark driver " Russell King - ARM Linux

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