linux-kernel - Re: [RFC v2 3/6] irq: bypass: Extend skeleton for ARM forwarding control

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Message-ID: <559AA552.3010400@redhat.com>
Date:	Mon, 6 Jul 2015 17:57:06 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Eric Auger <eric.auger@...aro.org>, eric.auger@...com,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
	kvm@...r.kernel.org, christoffer.dall@...aro.org,
	marc.zyngier@....com, alex.williamson@...hat.com,
	avi.kivity@...il.com, mtosatti@...hat.com, feng.wu@...el.com,
	joro@...tes.org, b.reynal@...tualopensystems.com
Cc:	linux-kernel@...r.kernel.org, patches@...aro.org
Subject: Re: [RFC v2 3/6] irq: bypass: Extend skeleton for ARM forwarding
 control



On 06/07/2015 17:35, Eric Auger wrote:
>>> diff --git a/kernel/irq/bypass.c b/kernel/irq/bypass.c
>>> >> index 5d0f92b..efadbe5 100644
>>> >> --- a/kernel/irq/bypass.c
>>> >> +++ b/kernel/irq/bypass.c
>>> >> @@ -19,6 +19,42 @@ static LIST_HEAD(producers);
>>> >>  static LIST_HEAD(consumers);
>>> >>  static DEFINE_MUTEX(lock);
>>> >>  
>>> >> +/* lock must be hold when calling connect */
>> > 
>> > If a lock must be held while callbacks are called, you have to document
>> > that producers and consumers must _not_ call back into the IRQ bypass
>> > manager.  (If they have to, you have to document explicitly "This
>> > function can be called from producer and consumer callbacks" whenever
>> > relevant).
> OK Thanks

Also, please document on functions that take the irq bypass mutex that
they can sleep.  In fact irq_bypass_{,un}register_{producer,consumer}
need kerneldoc comments.

The good thing is that this helps a bit forming a lock hierarchy across
the subsystems, for example irq bypass mutex outside vfio_platform_irq
spinlock, because you cannot have a spinlock inside the mutex.  I think
that all of your six callbacks are fine.

Paolo
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