[RFC PATCH 7/7] arm64: Add support for on-demand backtrace of other CPUs
From: Daniel Thompson
Date: Wed Mar 18 2015 - 10:22:44 EST
Currently arm64 has no implementation of arch_trigger_all_cpu_backtace.
The patch provides one for arm64 systems that are built with
CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS (i.e. those that have a pseudo-NMI).
Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/hardirq.h | 2 +-
arch/arm64/include/asm/irq.h | 5 +++
arch/arm64/include/asm/smp.h | 4 +++
arch/arm64/kernel/smp.c | 70 ++++++++++++++++++++++++++++++++++++++++
drivers/irqchip/irq-gic-v3.c | 28 ++++++++++++++++
6 files changed, 109 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 91c0babb6132..cb8d3dce73c3 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -76,6 +76,7 @@ config ARM64
select PERF_USE_VMALLOC
select POWER_RESET
select POWER_SUPPLY
+ select PRINTK_NMI_BACKTRACE if USE_ICC_SYSREGS_FOR_IRQFLAGS
select RTC_LIB
select SPARSE_IRQ
select SYSCTL_EXCEPTION_TRACE
diff --git a/arch/arm64/include/asm/hardirq.h b/arch/arm64/include/asm/hardirq.h
index 6aae421f4d73..e8a3268a891c 100644
--- a/arch/arm64/include/asm/hardirq.h
+++ b/arch/arm64/include/asm/hardirq.h
@@ -20,7 +20,7 @@
#include <linux/threads.h>
#include <asm/irq.h>
-#define NR_IPI 5
+#define NR_IPI 6
typedef struct {
unsigned int __softirq_pending;
diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index 94c53674a31d..4f974a2959bb 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -8,4 +8,9 @@ struct pt_regs;
extern void migrate_irqs(void);
extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
+#if defined CONFIG_SMP && defined CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+extern void arch_trigger_all_cpu_backtrace(bool);
+#define arch_trigger_all_cpu_backtrace(x) arch_trigger_all_cpu_backtrace(x)
+#endif
+
#endif
diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index 780f82c827b6..9b3b5663b88b 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -24,6 +24,10 @@
# error "<asm/smp.h> included in non-SMP build"
#endif
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+#define SMP_IPI_NMI_MASK (1 << 5)
+#endif
+
#define raw_smp_processor_id() (current_thread_info()->cpu)
struct seq_file;
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 328b8ce4b007..9369eee1fa9f 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -68,6 +68,7 @@ enum ipi_msg_type {
IPI_CPU_STOP,
IPI_TIMER,
IPI_IRQ_WORK,
+ IPI_CPU_BACKTRACE,
};
/*
@@ -485,6 +486,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = {
S(IPI_CPU_STOP, "CPU stop interrupts"),
S(IPI_TIMER, "Timer broadcast interrupts"),
S(IPI_IRQ_WORK, "IRQ work interrupts"),
+ S(IPI_CPU_BACKTRACE, "backtrace interrupts"),
};
static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
@@ -559,6 +561,66 @@ static void ipi_cpu_stop(unsigned int cpu)
cpu_relax();
}
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+
+/* For reliability, we're prepared to waste bits here. */
+static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
+
+void arch_trigger_all_cpu_backtrace(bool include_self)
+{
+ int i;
+ int this_cpu = get_cpu();
+
+ if (0 != printk_nmi_backtrace_prepare()) {
+ /*
+ * If there is already an nmi printk sequence in
+ * progress then just give up...
+ */
+ put_cpu();
+ return;
+ }
+
+ cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
+ if (!include_self)
+ cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
+
+ if (!cpumask_empty(to_cpumask(backtrace_mask))) {
+ pr_info("Sending NMI to %s CPUs:\n",
+ (include_self ? "all" : "other"));
+ smp_cross_call(to_cpumask(backtrace_mask), IPI_CPU_BACKTRACE);
+ }
+
+ /* Wait for up to 10 seconds for all CPUs to do the backtrace */
+ for (i = 0; i < 3 * 1000; i++) {
+ if (cpumask_empty(to_cpumask(backtrace_mask)))
+ break;
+ mdelay(1);
+ touch_softlockup_watchdog();
+ }
+
+ printk_nmi_backtrace_complete();
+ put_cpu();
+}
+
+void ipi_cpu_backtrace(struct pt_regs *regs)
+{
+ int cpu = smp_processor_id();
+
+ BUILD_BUG_ON(SMP_IPI_NMI_MASK != BIT(IPI_CPU_BACKTRACE));
+
+ if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
+ printk_nmi_backtrace_this_cpu_begin();
+ pr_warn("NMI backtrace for cpu %d\n", cpu);
+ show_regs(regs);
+ show_stack(NULL, NULL);
+ printk_nmi_backtrace_this_cpu_end();
+
+ cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
+ }
+}
+
+#endif /* CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS */
+
/*
* Main handler for inter-processor interrupts
*/
@@ -605,6 +667,14 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
break;
#endif
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ case IPI_CPU_BACKTRACE:
+ nmi_enter();
+ ipi_cpu_backtrace(regs);
+ nmi_exit();
+ break;
+#endif
+
default:
pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);
break;
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 3923b2a2150c..bdb134ed4519 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -34,6 +34,16 @@
#include "irq-gic-common.h"
#include "irqchip.h"
+#ifndef SMP_IPI_NMI_MASK
+#define SMP_IPI_NMI_MASK 0
+#endif
+
+/*
+ * Copied from arm-gic.h (which we cannot include here because it conflicts
+ * with arm-gic-v3.h)
+ */
+#define GIC_DIST_PRI 0x400
+
struct redist_region {
void __iomem *redist_base;
phys_addr_t phys_base;
@@ -438,6 +448,7 @@ static int gic_dist_supports_lpis(void)
static void gic_cpu_init(void)
{
void __iomem *rbase;
+ unsigned long nmimask, hwirq;
/* Register ourselves with the rest of the world */
if (gic_populate_rdist())
@@ -455,6 +466,23 @@ static void gic_cpu_init(void)
/* initialise system registers */
gic_cpu_sys_reg_init();
+
+ /* Boost the priority of any IPI in the mask */
+ nmimask = SMP_IPI_NMI_MASK;
+ for_each_set_bit(hwirq, &nmimask, 16) {
+ unsigned int pri_reg = (hwirq / 4) * 4;
+ u32 pri_mask = BIT(6 + ((hwirq % 4) * 8));
+ u32 pri_val = readl_relaxed(rbase + GIC_DIST_PRI + pri_reg);
+ u32 actual;
+
+ pri_mask |= BIT(7 + ((hwirq % 4) * 8));
+ pri_val &= ~pri_mask; /* priority boost */
+ writel_relaxed(pri_val, rbase + GIC_DIST_PRI + pri_reg);
+
+ actual = readl_relaxed(rbase + GIC_DIST_PRI + pri_reg);
+ }
+ gic_dist_wait_for_rwp();
+ gic_redist_wait_for_rwp();
}
#ifdef CONFIG_SMP
--
2.1.0
--
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