linux/kernel/irq
Pallipadi, Venkatesh 6ec3cfeca0 x86, irq: Remove IRQ_DISABLED check in process context IRQ move
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 932775a4ab
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: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Acked-by: "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: Ingo Molnar <mingo@elte.hu>
2009-04-14 15:21:13 +02:00
..
autoprobe.c async: Asynchronous function calls to speed up kernel boot 2009-01-07 08:45:46 -08:00
chip.c Merge branch 'core/percpu' into percpu-cpumask-x86-for-linus-2 2009-03-27 17:28:43 +01:00
devres.c genirq: add support for threaded interrupts to devres 2009-03-24 12:15:23 +01:00
handle.c Merge branch 'linus' into irq/threaded 2009-04-06 01:41:22 +02:00
internals.h PM: Introduce functions for suspending and resuming device interrupts 2009-03-30 21:46:54 +02:00
Makefile PM: Introduce functions for suspending and resuming device interrupts 2009-03-30 21:46:54 +02:00
manage.c x86, irq: Remove IRQ_DISABLED check in process context IRQ move 2009-04-14 15:21:13 +02:00
migration.c cpumask: update irq_desc to use cpumask_var_t 2009-01-11 19:12:46 +01:00
numa_migrate.c irq: fix cpumask memory leak on offstack cpumask kernels 2009-04-03 19:14:44 +02:00
pm.c PM: Introduce functions for suspending and resuming device interrupts 2009-03-30 21:46:54 +02:00
proc.c cpumask: update irq_desc to use cpumask_var_t 2009-01-11 19:12:46 +01:00
resend.c generic: sparse irqs: use irq_desc() together with dyn_array, instead of irq_desc[] 2008-10-16 16:52:29 +02:00
spurious.c irq: provide debug_poll_all_shared_irqs() method under CONFIG_DEBUG_SHIRQ 2009-01-16 17:46:49 +01:00