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Date: Thu, 20 Apr 2017 10:43:11 +0100 From: Marc Zyngier <marc.zyngier@....com> To: Mason <slash.tmp@...e.fr>, Thomas Gleixner <tglx@...utronix.de> Cc: Bjorn Helgaas <helgaas@...nel.org>, Robin Murphy <robin.murphy@....com>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, Liviu Dudau <liviu.dudau@....com>, David Laight <david.laight@...lab.com>, linux-pci <linux-pci@...r.kernel.org>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, Thibaud Cornic <thibaud_cornic@...madesigns.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [RFC PATCH v0.2] PCI: Add support for tango PCIe host bridge On 20/04/17 09:20, Mason wrote: > On 19/04/2017 13:19, Mason wrote: > >> My biggest problem is that tango_unmask() is never called. > > FTR, the missing incantation was: > Explicitly calling tango_{mask/unmask/ack} from the corresponding msi_{mask/unmask/ack} Using irq_chip_mask_parent and co, you mean? > Marc, I have one nagging doubt, wrt splitting MSI line selection > and MSI enable. > > tango_irq_domain_alloc : finds an available MSI 'j' to allocate > tango_irq_domain_free : release MSI 'j' > tango_unmask : enable MSI 'j' > tango_mask : disable MSI 'j' > > Is the following scenario guaranteed to never happen? > > tango_irq_domain_alloc // alloc 0 > tango_irq_domain_free // free 0 > tango_irq_domain_alloc // alloc 0 > tango_unmask // enable 0 > tango_unmask // enable 0 = NOP > tango_mask // disable 0 > > In this theoretical scenario, we would be left with a non-functional > MSI 0. I'm not sure I get the example above, and what the various alloc/free calls have to do with anything. If you have unbalanced enable/disable_irq, you loose. Don't do that. M. -- Jazz is not dead. It just smells funny...
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