Messages in this thread | | | Date | Wed, 10 Sep 2014 22:08:00 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [Patch v4 14/16] x86, irq: Introduce helper to check whether an IOAPIC has been registered |
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On Wed, 10 Sep 2014, Jiang Liu wrote: > On 2014/9/9 20:37, Thomas Gleixner wrote: > >> + ret = mp_ioapic_registered(gsi_base); > >> + up_write(&acpi_ioapic_rwsem); > >> + > >> + return ret; > >> +} > > > > So I assume that this is for a particular caller in the apci ioapic > > hotplug code and that call site has its own serialization. Otherwise > > the return value is not protected at all. > > > > Please add a Docbook comment to that function, and document the > > locking rules as thats pretty non obvious. > How about this comments about locking rules? > /* > * Locks related to IOAPIC hotplug > * Hotplug side: > * ->lock_device_hotplug() //device_hotplug_lock > * ->acpi_ioapic_rwsem > * ->ioapic_lock > * Interrupt mapping side: > * ->acpi_ioapic_rwsem > * ->ioapic_mutex > * ->ioapic_lock > */
That looks asymetric. Why is the hotplug side not taking ioapic_mutex?
Thanks,
tglx
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