diff options
Diffstat (limited to 'debian/patches-rt/0039-arm-Disable-jump-label-on-PREEMPT_RT.patch')
| -rw-r--r-- | debian/patches-rt/0039-arm-Disable-jump-label-on-PREEMPT_RT.patch | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/debian/patches-rt/0039-arm-Disable-jump-label-on-PREEMPT_RT.patch b/debian/patches-rt/0039-arm-Disable-jump-label-on-PREEMPT_RT.patch new file mode 100644 index 000000000..ac47159c4 --- /dev/null +++ b/debian/patches-rt/0039-arm-Disable-jump-label-on-PREEMPT_RT.patch @@ -0,0 +1,42 @@ +From f1c0950a69e46ee1d45192bfae026622da60bdc8 Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner <tglx@linutronix.de> +Date: Wed, 8 Jul 2015 17:14:48 +0200 +Subject: [PATCH 39/62] arm: Disable jump-label on PREEMPT_RT. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.1/older/patches-6.1.69-rt21.tar.xz + +jump-labels are used to efficiently switch between two possible code +paths. To achieve this, stop_machine() is used to keep the CPU in a +known state while the opcode is modified. The usage of stop_machine() +here leads to large latency spikes which can be observed on PREEMPT_RT. + +Jump labels may change the target during runtime and are not restricted +to debug or "configuration/ setup" part of a PREEMPT_RT system where +high latencies could be defined as acceptable. + +Disable jump-label support on a PREEMPT_RT system. + +[bigeasy: Patch description.] + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Link: https://lkml.kernel.org/r/20220613182447.112191-2-bigeasy@linutronix.de +--- + arch/arm/Kconfig | 2 +- + 1 file changed, 1 insertion(+), 1 deletion(-) + +diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig +index 717e596dc13b..f170f29e98ac 100644 +--- a/arch/arm/Kconfig ++++ b/arch/arm/Kconfig +@@ -71,7 +71,7 @@ config ARM + select HARDIRQS_SW_RESEND + select HAVE_ARCH_AUDITSYSCALL if AEABI && !OABI_COMPAT + select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6 +- select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU ++ select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU && !PREEMPT_RT + select HAVE_ARCH_KFENCE if MMU && !XIP_KERNEL + select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU + select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL +-- +2.43.0 + |