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Commit e509bd7d authored by Mika Westerberg's avatar Mika Westerberg Committed by Thomas Gleixner
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genirq: Allow migration of chained interrupts by installing default action



When a CPU is offlined all interrupts that have an action are migrated to
other still online CPUs. However, if the interrupt has chained handler
installed this is not done. Chained handlers are used by GPIO drivers which
support interrupts, for instance.

When the affinity is not corrected properly we end up in situation where
most interrupts are not arriving to the online CPUs anymore. For example on
Intel Braswell system which has SD-card card detection signal connected to
a GPIO the IO-APIC routing entries look like below after CPU1 is offlined:

  pin30, enabled , level, low , V(52), IRR(0), S(0), logical , D(03), M(1)
  pin31, enabled , level, low , V(42), IRR(0), S(0), logical , D(03), M(1)
  pin32, enabled , level, low , V(62), IRR(0), S(0), logical , D(03), M(1)
  pin5b, enabled , level, low , V(72), IRR(0), S(0), logical , D(03), M(1)

The problem here is that the destination mask still contains both CPUs even
if CPU1 is already offline. This means that the IO-APIC still routes
interrupts to the other CPU as well.

We solve the problem by providing a default action for chained interrupts.
This action allows the migration code to correct affinity (as it finds
desc->action != NULL).

Also make the default action handler to emit a warning if for some reason a
chained handler ends up calling it.

Signed-off-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Link: http://lkml.kernel.org/r/1444039935-30475-1-git-send-email-mika.westerberg@linux.intel.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 9e7e2b0a
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