37 lines
1.6 KiB
Diff
37 lines
1.6 KiB
Diff
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 8 Jul 2015 17:14:48 +0200
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Subject: [PATCH 1/2] arm: Disable jump-label on PREEMPT_RT.
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz
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jump-labels are used to efficiently switch between two possible code
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paths. To achieve this, stop_machine() is used to keep the CPU in a
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known state while the opcode is modified. The usage of stop_machine()
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here leads to large latency spikes which can be observed on PREEMPT_RT.
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Jump labels may change the target during runtime and are not restricted
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to debug or "configuration/ setup" part of a PREEMPT_RT system where
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high latencies could be defined as acceptable.
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Disable jump-label support on a PREEMPT_RT system.
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[bigeasy: Patch description.]
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Link: https://lkml.kernel.org/r/20220613182447.112191-2-bigeasy@linutronix.de
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---
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arch/arm/Kconfig | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/arch/arm/Kconfig
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+++ b/arch/arm/Kconfig
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@@ -78,7 +78,7 @@ config ARM
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select HAS_IOPORT
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select HAVE_ARCH_AUDITSYSCALL if AEABI && !OABI_COMPAT
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select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
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- select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
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+ select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU && !PREEMPT_RT
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select HAVE_ARCH_KFENCE if MMU && !XIP_KERNEL
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select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
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select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
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