genirq/affinity: Defer affinity setting if irq chip is busy

The case that interrupt affinity setting fails with -EBUSY can be handled
in the kernel completely by using the already available generic pending
infrastructure.

If a irq_chip::set_affinity() fails with -EBUSY, handle it like the
interrupts for which irq_chip::set_affinity() can only be invoked from
interrupt context. Copy the new affinity mask to irq_desc::pending_mask and
set the affinity pending bit. The next raised interrupt for the affected
irq will check the pending bit and try to set the new affinity from the
handler. This avoids that -EBUSY is returned when an affinity change is
requested from user space and the previous change has not been cleaned
up. The new affinity will take effect when the next interrupt is raised
from the device.

Fixes: dccfe3147b42 ("x86/vector: Simplify vector move cleanup")
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Song Liu <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Cc: [email protected]
Cc: Mike Travis <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Tariq Toukan <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

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