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powerpc: Re-enable dynticks 

Implement arch_irq_work_has_interrupt() for powerpc

Commit 9b01f5bf3 introduced a dependency on "IRQ work self-IPIs" for
full dynamic ticks to be enabled, by expecting architectures to
implement a suitable arch_irq_work_has_interrupt() routine.

Several arches have implemented this routine, including x86 (3010279f)
and arm (09f6edd4), but powerpc was omitted.

This patch implements this routine for powerpc.

The symptom, at boot (on powerpc systems) with "nohz_full=<CPU list>"
is displayed:

     NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs

after this patch:

     NO_HZ: Full dynticks CPUs: <CPU list>.

Tested against 3.19.

powerpc implements "IRQ work self-IPIs" by setting the decrementer to 1 in
arch_irq_work_raise(), which causes a decrementer exception on the next
timebase tick. We then handle the work in __timer_interrupt().

CC: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul A. Clarke <pc@us.ibm.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[mpe: Flesh out change log, fix ws & include guards, remove include of processor.h]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Paul Clarke 2015-02-20 11:13:33 -06:00 committed by Michael Ellerman
parent c517d838eb
commit fea559f303
1 changed files with 9 additions and 0 deletions
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9
arch/powerpc/include/asm/irq_work.h Normal file
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#ifndef _ASM_POWERPC_IRQ_WORK_H
#define _ASM_POWERPC_IRQ_WORK_H
static inline bool arch_irq_work_has_interrupt(void)
{
return true;
}
#endif /* _ASM_POWERPC_IRQ_WORK_H */