linux-kernel - [RFC PATCH 2/3] arm: kgdb: Add support for IPI FIQ roundup

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Date:	Thu, 14 Aug 2014 12:15:50 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Russell King <linux@....linux.org.uk>
Cc:	Daniel Thompson <daniel.thompson@...aro.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kgdb-bugreport@...ts.sourceforge.net, patches@...aro.org,
	linaro-kernel@...ts.linaro.org,
	John Stultz <john.stultz@...aro.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Colin Cross <ccross@...roid.com>, kernel-team@...roid.com,
	Rob Herring <robherring2@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Martin <Dave.Martin@....com>,
	Fabio Estevam <festevam@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Nicolas Pitre <nico@...aro.org>
Subject: [RFC PATCH 2/3] arm: kgdb: Add support for IPI FIQ roundup

Rounding up the other CPUs using FIQ improves debugger robustness.

Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
---
 arch/arm/include/asm/kgdb.h |  1 +
 arch/arm/kernel/kgdb.c      | 20 ++++++++++++++++----
 arch/arm/kernel/kgdb_fiq.c  |  7 ++++++-
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/arm/include/asm/kgdb.h b/arch/arm/include/asm/kgdb.h
index 5de21f01..ceb466f 100644
--- a/arch/arm/include/asm/kgdb.h
+++ b/arch/arm/include/asm/kgdb.h
@@ -50,6 +50,7 @@ static inline void arch_kgdb_breakpoint(void)
 extern void kgdb_handle_bus_error(void);
 extern int kgdb_fault_expected;
 
+extern int kgdb_fiq_enabled;
 extern char kgdb_fiq_handler;
 extern char kgdb_fiq_handler_end;
 asmlinkage void __exception_irq_entry kgdb_fiq_do_handle(struct pt_regs *regs);
diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
index a74b53c..e5c3ec0 100644
--- a/arch/arm/kernel/kgdb.c
+++ b/arch/arm/kernel/kgdb.c
@@ -175,14 +175,26 @@ static struct undef_hook kgdb_compiled_brkpt_hook = {
 
 static void kgdb_call_nmi_hook(void *ignored)
 {
-       kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
+	kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
 }
 
 void kgdb_roundup_cpus(unsigned long flags)
 {
-       local_irq_enable();
-       smp_call_function(kgdb_call_nmi_hook, NULL, 0);
-       local_irq_disable();
+#ifdef CONFIG_FIQ
+	struct cpumask mask;
+
+	if (kgdb_fiq_enabled) {
+		cpumask_copy(&mask, cpu_online_mask);
+		cpumask_clear_cpu(raw_smp_processor_id(), &mask);
+		if (!cpumask_empty(&mask))
+			send_fiq_ipi_mask(&mask);
+		return;
+	}
+#endif
+
+	local_irq_enable();
+	smp_call_function(kgdb_call_nmi_hook, NULL, 0);
+	local_irq_disable();
 }
 
 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
diff --git a/arch/arm/kernel/kgdb_fiq.c b/arch/arm/kernel/kgdb_fiq.c
index a894dde..f7a2c3d 100644
--- a/arch/arm/kernel/kgdb_fiq.c
+++ b/arch/arm/kernel/kgdb_fiq.c
@@ -24,7 +24,7 @@
 #include <asm/fiq.h>
 #include <asm/exception.h>
 
-static int kgdb_fiq_enabled;
+int kgdb_fiq_enabled;
 module_param_named(enable, kgdb_fiq_enabled, int, 0600);
 MODULE_PARM_DESC(enable, "set to 1 to enable FIQ KGDB");
 
@@ -40,6 +40,11 @@ asmlinkage void __exception_irq_entry kgdb_fiq_do_handle(struct pt_regs *regs)
 {
 	int actual;
 
+	if (!kgdb_nmicallback(raw_smp_processor_id(), regs)) {
+		handle_IPI_FIQ(regs);
+		return;
+	}
+
 	nmi_enter();
 	actual = ack_fiq(kgdb_fiq);
 	WARN_ON(actual != kgdb_fiq);
-- 
1.9.3

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