• Pallipadi, Venkatesh's avatar
    x86, irq: Remove IRQ_DISABLED check in process context IRQ move · 6ec3cfec
    Pallipadi, Venkatesh authored
    As discussed in the thread here:
    
      http://marc.info/?l=linux-kernel&m=123964468521142&w=2
    
    Eric W. Biederman observed:
    
    > It looks like some additional bugs have slipped in since last I looked.
    >
    > set_irq_affinity does this:
    > ifdef CONFIG_GENERIC_PENDING_IRQ
    >        if (desc->status & IRQ_MOVE_PCNTXT || desc->status & IRQ_DISABLED) {
    >                cpumask_copy(desc->affinity, cpumask);
    >                desc->chip->set_affinity(irq, cpumask);
    >        } else {
    >                desc->status |= IRQ_MOVE_PENDING;
    >                cpumask_copy(desc->pending_mask, cpumask);
    >        }
    > #else
    >
    > That IRQ_DISABLED case is a software state and as such it has nothing to
    > do with how safe it is to move an irq in process context.
    
    [...]
    
    >
    > The only reason we migrate MSIs in interrupt context today is that there
    > wasn't infrastructure for support migration both in interrupt context
    > and outside of it.
    
    Yes. The idea here was to force the MSI migration to happen in process
    context. One of the patches in the series did
    
            disable_irq(dev->irq);
            irq_set_affinity(dev->irq, cpumask_of(dev->cpu));
            enable_irq(dev->irq);
    
    with the above patch adding irq/manage code check for interrupt disabled
    and moving the interrupt in process context.
    
    IIRC, there was no IRQ_MOVE_PCNTXT when we were developing this HPET
    code and we ended up having this ugly hack. IRQ_MOVE_PCNTXT was there
    when we eventually submitted the patch upstream. But, looks like I did a
    blind rebasing instead of using IRQ_MOVE_PCNTXT in hpet MSI code.
    
    Below patch fixes this. i.e., revert commit 932775a4
    and add PCNTXT to HPET MSI setup. Also removes copying of desc->affinity
    in generic code as set_affinity routines are doing it internally.
    Reported-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
    Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    Cc: "Li Shaohua" <shaohua.li@intel.com>
    Cc: Gary Hade <garyhade@us.ibm.com>
    Cc: "lcm@us.ibm.com" <lcm@us.ibm.com>
    Cc: suresh.b.siddha@intel.com
    LKML-Reference: <20090413222058.GB8211@linux-os.sc.intel.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    6ec3cfec
io_apic.c 99.1 KB