arm64: smp: Add function to determine if cpus are stuck in the kernel

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kernel/smp.c has a fancy counter that keeps track of the number of CPUs
it marked as not-present and left in cpu_park_loop(). If there are any
CPUs spinning in here, features like kexec or hibernate may release them
by overwriting this memory.

This problem also occurs on machines using spin-tables to release
secondary cores.
After commit 44dbcc93ab ("arm64: Fix behavior of maxcpus=N")
we bring all known cpus into the secondary holding pen, meaning this
memory can't be re-used by kexec or hibernate.

Add a function cpus_are_stuck_in_kernel() to determine if either of these
cases have occurred.

Signed-off-by: James Morse <james.morse@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

...

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James Morse 2016-06-22 10:06:12 +01:00 • committed by Will Deacon

parent 20c27a4270

commit 5c492c3f52

2 changed files with 30 additions and 0 deletions

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12

arch/arm64/include/asm/smp.h

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18

arch/arm64/kernel/smp.c

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