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authorDaniel Thompson <daniel.thompson@linaro.org>2015-12-18 11:53:37 +0000
committerDaniel Thompson <daniel.thompson@linaro.org>2016-08-11 12:48:12 +0100
commit2af5ebfc75d6cca56209b649782a303ca9b211dd (patch)
tree8eb9f290a38a8a01c7aaf7fb9297e823a7052b38
parent9b1b985f6c8e5e01bf93105117a5cd5c5f8c9e6a (diff)
downloadlinux-dev/trigger_backtrace-v4.8.tar.gz
ARM: Allow IPI_CPU_BACKTRACE to exploit FIQdev/trigger_backtrace-v4.8
The GIC (v1 & v2) driver allows its implementation of handle_arch_irq() to be called from the FIQ handler but currently the ARM code is not able to exploit this. Extend handle_fiq_as_nmi() to call handle_arch_irq(). This will affect all interrupt controllers, including ones that do not support FIQ. This is OK because a spurious FIQ is normally fatal. Handling a spurious FIQ like a normal interrupt does risk deadlock but does give us a chance of surviving long enough to get an error message out. We also extend the SMP code to indicate to irq drivers which IPIs they should seek to implement using FIQ. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
-rw-r--r--arch/arm/include/asm/smp.h9
-rw-r--r--arch/arm/kernel/smp.c6
-rw-r--r--arch/arm/kernel/traps.c11
3 files changed, 25 insertions, 1 deletions
diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index 3d6dc8b460e4..daf869cff02e 100644
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -18,6 +18,15 @@
# error "<asm/smp.h> included in non-SMP build"
#endif
+/*
+ * Identify which IPIs are safe for the irqchip to handle using FIQ.
+ *
+ * This information is advisory. The interrupt controller may not be capable
+ * of routing these IPIs to FIQ and the kernel will continue to work if they
+ * are routed to IRQ as normal.
+ */
+#define SMP_IPI_FIQ_MASK 0x80
+
#define raw_smp_processor_id() (current_thread_info()->cpu)
struct seq_file;
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 861521606c6d..5e955ad80a1e 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -644,6 +644,11 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
break;
case IPI_CPU_BACKTRACE:
+ if (in_nmi()) {
+ nmi_cpu_backtrace(regs);
+ break;
+ }
+
printk_nmi_enter();
irq_enter();
nmi_cpu_backtrace(regs);
@@ -757,6 +762,7 @@ static void raise_nmi(cpumask_t *mask)
if (cpumask_test_cpu(smp_processor_id(), mask) && irqs_disabled())
nmi_cpu_backtrace(NULL);
+ BUILD_BUG_ON(SMP_IPI_FIQ_MASK != BIT(IPI_CPU_BACKTRACE));
smp_cross_call(mask, IPI_CPU_BACKTRACE);
}
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index bc698383e822..8f6173cd0a54 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -479,7 +479,16 @@ asmlinkage void __exception_irq_entry handle_fiq_as_nmi(struct pt_regs *regs)
nmi_enter();
- /* nop. FIQ handlers for special arch/arm features can be added here. */
+ /*
+ * Either the interrupt controller supports FIQ, meaning it will
+ * do the right thing with this call, or we will end up treating a
+ * spurious FIQ (which is normally fatal) as though it were an IRQ
+ * which, although it risks deadlock, still gives us a sporting
+ * chance of surviving long enough to log errors.
+ */
+#ifdef CONFIG_MULTI_IRQ_HANDLER
+ handle_arch_irq(regs);
+#endif
nmi_exit();