linux-kernel - Re: [PATCH v4] lib: cpu_rmap: avoid flushing all workqueues

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Message-ID: <1357661117.2750.1.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Tue, 8 Jan 2013 16:05:17 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	David Decotigny <decot@...glers.com>,
	<linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Josh Triplett <josh@...htriplett.org>,
	David Howells <dhowells@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: Re: [PATCH v4] lib: cpu_rmap: avoid flushing all workqueues

On Thu, 2013-01-03 at 13:58 -0800, Andrew Morton wrote:
> On Wed, 2 Jan 2013 23:46:46 +0000
> Ben Hutchings <bhutchings@...arflare.com> wrote:
[...]
> > >   drivers/net/ethernet/mellanox/mlx4/ appears to be using
> > >   msix_ctl.pool_lock for exclusion, but I didn't check for coverage.
> > >
> > >   drivers/net/ethernet/sfc/efx.c seems to not need locking because
> > >   all its cpu_rmap operations are at module_init() time.
> > >
> > >   The cpu_rmap code would be less of a hand grenade if each of its
> > >   interface functions documented the caller's locking requirements.
> > 
> > This particular 'hand grenade' *was* documented.  So I don't think
> > documentation is the problem.
> 
> Dunno what you're referring to here.  There is no cpu_rmap() locking
> documentation.
[...]

/**
 * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
 * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
 *
 * Must be called in process context, before freeing the IRQs, and
 * without holding any locks required by global workqueue items.
 */

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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