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 <rmk+kernel@xxxxxxxxxxxxxxx>
---
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();
+ }
}
/**
--
2.7.4
--
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