powerpc: allow soft-NMI watchdog to cover timer interrupts with large decrementers

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Large decrementers (e.g., POWER9) can take a very long time to wrap,
so when the timer iterrupt handler sets the decrementer to max so as
to avoid taking another decrementer interrupt when hard enabling
interrupts before running timers, it effectively disables the soft
NMI coverage for timer interrupts.

Fix this by using the traditional 31-bit value instead, which wraps
after a few seconds. masked interrupt code does the same thing, and
in normal operation neither of these paths would ever wrap even the
31 bit value.

Note: the SMP watchdog should catch timer interrupt lockups, but it
is preferable for the local soft-NMI to catch them, mainly to avoid
the IPI.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

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Nicholas Piggin 2018-05-05 03:19:32 +10:00 • committed by Michael Ellerman

parent 3f984620f9

commit a7cba02dec

1 changed files with 13 additions and 6 deletions

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arch/powerpc/kernel/time.c

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