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| author | James Morse <james.morse@arm.com> | 2016-06-22 10:06:12 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-06-27 16:24:51 +0100 |
| commit | b69e0dc14ce3c4abbd11725ff98a885d4616f9fe (patch) | |
| tree | a3ef54f76d88dfd7632f2a6504ef4aeb7242b5fd /arch/arm64/include | |
| parent | d770b5a04790a4ec1c0864621eef95f5afe773cf (diff) | |
| download | linux-b69e0dc14ce3c4abbd11725ff98a885d4616f9fe.tar.bz2 | |
arm64: smp: Add function to determine if cpus are stuck in the kernel
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 44dbcc93ab67 ("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>
[catalin.marinas@arm.com: cherry-picked from mainline for kexec dependency]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/smp.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h index 433e50405274..022644704a93 100644 --- a/arch/arm64/include/asm/smp.h +++ b/arch/arm64/include/asm/smp.h @@ -124,6 +124,18 @@ static inline void cpu_panic_kernel(void) cpu_park_loop(); } +/* + * If a secondary CPU enters the kernel but fails to come online, + * (e.g. due to mismatched features), and cannot exit the kernel, + * we increment cpus_stuck_in_kernel and leave the CPU in a + * quiesecent loop within the kernel text. The memory containing + * this loop must not be re-used for anything else as the 'stuck' + * core is executing it. + * + * This function is used to inhibit features like kexec and hibernate. + */ +bool cpus_are_stuck_in_kernel(void); + #endif /* ifndef __ASSEMBLY__ */ #endif /* ifndef __ASM_SMP_H */ |