[PATCH v2] ARM: avoid Cortex-A9 livelock on tight dmb loops
From: Russell King <hidden>
Date: 2018-06-01 11:00:16
Also in:
linux-omap
Subsystem:
arm port, omap powerdomain soc adaptation layer support, omap2+ support, the rest · Maintainers:
Russell King, Paul Walmsley, Aaro Koskinen, Andreas Kemnade, Kevin Hilman, Roger Quadros, Tony Lindgren, Linus Torvalds
Executing loops such as: while (1) cpu_relax(); with interrupts disabled results in a livelock of the entire system, as other CPUs are prevented making progress. This is most noticable as a failure of crashdump kexec, which stops just after issuing: Loading crashdump kernel... to the system console. Two other locations of these loops within the ARM code have been identified and fixed up. Signed-off-by: Russell King <redacted> --- v2: use wfe() instead of cpu_do_idle arch/arm/include/asm/barrier.h | 2 ++ arch/arm/kernel/machine_kexec.c | 5 ++++- arch/arm/kernel/smp.c | 4 +++- arch/arm/mach-omap2/prm_common.c | 4 +++- 4 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h
index 69772e742a0a..83ae97c049d9 100644
--- a/arch/arm/include/asm/barrier.h
+++ b/arch/arm/include/asm/barrier.h@@ -11,6 +11,8 @@ #define sev() __asm__ __volatile__ ("sev" : : : "memory") #define wfe() __asm__ __volatile__ ("wfe" : : : "memory") #define wfi() __asm__ __volatile__ ("wfi" : : : "memory") +#else +#define wfe() do { } while (0) #endif #if __LINUX_ARM_ARCH__ >= 7
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index dd2eb5f76b9f..76300f3813e8 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c@@ -91,8 +91,11 @@ void machine_crash_nonpanic_core(void *unused) set_cpu_online(smp_processor_id(), false); atomic_dec(&waiting_for_crash_ipi); - while (1) + + while (1) { cpu_relax(); + wfe(); + } } void crash_smp_send_stop(void)
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 9ec9a366ef44..a39fe6ab89a2 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c@@ -570,8 +570,10 @@ static void ipi_cpu_stop(unsigned int cpu) local_fiq_disable(); local_irq_disable(); - while (1) + while (1) { cpu_relax(); + wfe(); + } } static DEFINE_PER_CPU(struct completion *, cpu_completion);
diff --git a/arch/arm/mach-omap2/prm_common.c b/arch/arm/mach-omap2/prm_common.c
index 021b5a8b9c0a..bb15a9eec05c 100644
--- a/arch/arm/mach-omap2/prm_common.c
+++ b/arch/arm/mach-omap2/prm_common.c@@ -522,8 +522,10 @@ void omap_prm_reset_system(void) prm_ll_data->reset_system(); - while (1) + while (1) { cpu_relax(); + wfe(); + } } /**
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2.7.4