powerpc: NMI IPI make NMI IPIs fully sychronous

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There is an asynchronous aspect to smp_send_nmi_ipi. The caller waits
for all CPUs to call in to the handler, but it does not wait for
completion of the handler. This is a needless complication, so remove
it and always wait synchronously.

The synchronous wait allows the caller to easily time out and clear
the wait for completion (zero nmi_ipi_busy_count) in the case of badly
behaved handlers. This would have prevented the recent smp_send_stop
NMI IPI bug from causing the system to hang.

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

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Nicholas Piggin 2018-04-25 15:17:59 +10:00 • committed by Michael Ellerman

parent 9b81c0211c

commit 5b73151fff

3 changed files with 27 additions and 25 deletions

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1

arch/powerpc/include/asm/smp.h

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44

arch/powerpc/kernel/smp.c

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1

arch/powerpc/kernel/watchdog.c

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