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Subject: Re: [PATCH v2] platform-msi: Free descriptors in
 platform_msi_domain_free()
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Nadav Haklai <nadavh@marvell.com>,
        Gregory Clement <gregory.clement@bootlin.com>,
        Maxime Chevallier <maxime.chevallier@bootlin.com>,
        Antoine Tenart <antoine.tenart@bootlin.com>,
        Stefan Chulski <stefanc@marvell.com>, stable@vger.kernel.org
References: <20181011091234.9605-1-miquel.raynal@bootlin.com>
From: Marc Zyngier <marc.zyngier@arm.com>
Message-ID: <2422611e-5d39-d0df-dc09-5b54cd02c9d8@arm.com>
Date: Fri, 12 Oct 2018 11:24:23 +0100
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Hi Miquel,

On 11/10/18 10:12, Miquel Raynal wrote:
> Since the addition of platform MSI support, there were two helpers
> supposed to allocate/free IRQs for a device:
> 
>      platform_msi_domain_alloc_irqs()
>      platform_msi_domain_free_irqs()
> 
> In these helpers, IRQ descriptors are allocated in the "alloc" routine
> while they are freed in the "free" one.
> 
> Later, two other helpers have been added to handle IRQ domains on top
> of MSI domains:
> 
>      platform_msi_domain_alloc()
>      platform_msi_domain_free()
> 
> Seen from the outside, the logic is pretty close with the former
> helpers and people used it with the same logic as before: a
> platform_msi_domain_alloc() call should be balanced with a
> platform_msi_domain_free() call. While this is probably what was
> intended to do, the platform_msi_domain_free() does not remove/free
> the IRQ descriptor(s) created/inserted in
> platform_msi_domain_alloc().
> 
> One effect of such situation is that removing a module that requested
> an IRQ will let one orphaned IRQ descriptor (with an allocated MSI
> entry) in the device descriptors list. Next time the module will be
> inserted back, one will observe that the allocation will happen twice
> in the MSI domain, one time for the remaining descriptor, one time for
> the new one. It also has the side effect to quickly overshoot the
> maximum number of allocated MSI and then prevent any module requesting
> an interrupt in the same domain to be inserted anymore.
> 
> This situation has been met with loops of insertion/removal of the
> mvpp2.ko module (requesting 15 MSIs each time).
> 
> Fixes: 552c494a7666 ("platform-msi: Allow creation of a MSI-based stacked irq domain")
> Cc: stable@vger.kernel.org
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Thanks for the respin. If nobody disagrees, I'll route this through 
Thomas to stash into tip, and hopefully have that in 4.19.

	M.
-- 
Jazz is not dead. It just smells funny...