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From:   Douglas Anderson <dianders@chromium.org>
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        Sumit Garg <sumit.garg@linaro.org>,
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Subject: [PATCH v8 04/10] nmi: backtrace: Allow runtime arch specific override
Date:   Wed, 19 Apr 2023 15:55:58 -0700
Message-ID: <20230419155341.v8.4.I3929b13cb2fab48772537aa308cd89e6f8a6753c@changeid>
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From: Sumit Garg <sumit.garg@linaro.org>

Add a boolean return to arch_trigger_cpumask_backtrace() to support a
use-case where a particular architecture detects at runtime if it supports
NMI backtrace or it would like to fallback to default implementation using
SMP cross-calls.

Currently such an architecture example is arm64 supporting pseudo NMIs
feature which is only available on platforms which have support for GICv3
or later version.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v8:
- Add loongarch support, too

 arch/arm/include/asm/irq.h       |  2 +-
 arch/arm/kernel/smp.c            |  3 ++-
 arch/loongarch/include/asm/irq.h |  2 +-
 arch/loongarch/kernel/process.c  |  3 ++-
 arch/mips/include/asm/irq.h      |  2 +-
 arch/mips/kernel/process.c       |  3 ++-
 arch/powerpc/include/asm/nmi.h   |  2 +-
 arch/powerpc/kernel/stacktrace.c |  3 ++-
 arch/sparc/include/asm/irq_64.h  |  2 +-
 arch/sparc/kernel/process_64.c   |  4 +++-
 arch/x86/include/asm/irq.h       |  2 +-
 arch/x86/kernel/apic/hw_nmi.c    |  3 ++-
 include/linux/nmi.h              | 12 ++++--------
 13 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
index a7c2337b0c7d..e6b62c7d6f0e 100644
--- a/arch/arm/include/asm/irq.h
+++ b/arch/arm/include/asm/irq.h
@@ -32,7 +32,7 @@ void init_IRQ(void);
 #ifdef CONFIG_SMP
 #include <linux/cpumask.h>
 
-extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
+extern bool arch_trigger_cpumask_backtrace(const cpumask_t *mask,
 					   bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 0b8c25763adc..acb97d9219b1 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -849,7 +849,8 @@ static void raise_nmi(cpumask_t *mask)
 	__ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask);
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_nmi);
+	return true;
 }
diff --git a/arch/loongarch/include/asm/irq.h b/arch/loongarch/include/asm/irq.h
index a115e8999c69..c7a152d6bf0c 100644
--- a/arch/loongarch/include/asm/irq.h
+++ b/arch/loongarch/include/asm/irq.h
@@ -40,7 +40,7 @@ void spurious_interrupt(void);
 #define NR_IRQS_LEGACY 16
 
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
-void arch_trigger_cpumask_backtrace(const struct cpumask *mask, bool exclude_self);
+bool arch_trigger_cpumask_backtrace(const struct cpumask *mask, bool exclude_self);
 
 #define MAX_IO_PICS 2
 #define NR_IRQS	(64 + (256 * MAX_IO_PICS))
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index fa2443c7afb2..8f7f818f5c4e 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -339,9 +339,10 @@ static void raise_backtrace(cpumask_t *mask)
 	}
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace);
+	return true;
 }
 
 #ifdef CONFIG_64BIT
diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
index 44f9824c1d8c..daf16173486a 100644
--- a/arch/mips/include/asm/irq.h
+++ b/arch/mips/include/asm/irq.h
@@ -77,7 +77,7 @@ extern int cp0_fdc_irq;
 
 extern int get_c0_fdc_int(void);
 
-void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
 				    bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 093dbbd6b843..7d538571830a 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -750,9 +750,10 @@ static void raise_backtrace(cpumask_t *mask)
 	}
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace);
+	return true;
 }
 
 int mips_get_process_fp_mode(struct task_struct *task)
diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h
index c3c7adef74de..135f65adcf63 100644
--- a/arch/powerpc/include/asm/nmi.h
+++ b/arch/powerpc/include/asm/nmi.h
@@ -12,7 +12,7 @@ static inline void watchdog_nmi_set_timeout_pct(u64 pct) {}
 #endif
 
 #ifdef CONFIG_NMI_IPI
-extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
+extern bool arch_trigger_cpumask_backtrace(const cpumask_t *mask,
 					   bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif
diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
index 5de8597eaab8..0fee4bded7ba 100644
--- a/arch/powerpc/kernel/stacktrace.c
+++ b/arch/powerpc/kernel/stacktrace.c
@@ -221,8 +221,9 @@ static void raise_backtrace_ipi(cpumask_t *mask)
 	}
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
+	return true;
 }
 #endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */
diff --git a/arch/sparc/include/asm/irq_64.h b/arch/sparc/include/asm/irq_64.h
index 154df2cf19f4..00a0051a9da0 100644
--- a/arch/sparc/include/asm/irq_64.h
+++ b/arch/sparc/include/asm/irq_64.h
@@ -87,7 +87,7 @@ static inline unsigned long get_softint(void)
 	return retval;
 }
 
-void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
 				    bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 
diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
index 91c2b8124527..f9aea1df3adf 100644
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -236,7 +236,7 @@ static void __global_reg_poll(struct global_reg_snapshot *gp)
 	}
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	struct thread_info *tp = current_thread_info();
 	struct pt_regs *regs = get_irq_regs();
@@ -291,6 +291,8 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 	memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
 
 	spin_unlock_irqrestore(&global_cpu_snapshot_lock, flags);
+
+	return true;
 }
 
 #ifdef CONFIG_MAGIC_SYSRQ
diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index 768aa234cbb4..f731638cc38e 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -43,7 +43,7 @@ extern void init_ISA_irqs(void);
 extern void __init init_IRQ(void);
 
 #ifdef CONFIG_X86_LOCAL_APIC
-void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
 				    bool exclude_self);
 
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 34a992e275ef..e7dcd28bc824 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -34,10 +34,11 @@ static void nmi_raise_cpu_backtrace(cpumask_t *mask)
 	apic->send_IPI_mask(mask, NMI_VECTOR);
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self,
 				      nmi_raise_cpu_backtrace);
+	return true;
 }
 
 static int nmi_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 048c0b9aa623..7d8a77cd1e03 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -145,26 +145,22 @@ static inline void touch_nmi_watchdog(void)
 #ifdef arch_trigger_cpumask_backtrace
 static inline bool trigger_all_cpu_backtrace(void)
 {
-	arch_trigger_cpumask_backtrace(cpu_online_mask, false);
-	return true;
+	return arch_trigger_cpumask_backtrace(cpu_online_mask, false);
 }
 
 static inline bool trigger_allbutself_cpu_backtrace(void)
 {
-	arch_trigger_cpumask_backtrace(cpu_online_mask, true);
-	return true;
+	return arch_trigger_cpumask_backtrace(cpu_online_mask, true);
 }
 
 static inline bool trigger_cpumask_backtrace(struct cpumask *mask)
 {
-	arch_trigger_cpumask_backtrace(mask, false);
-	return true;
+	return arch_trigger_cpumask_backtrace(mask, false);
 }
 
 static inline bool trigger_single_cpu_backtrace(int cpu)
 {
-	arch_trigger_cpumask_backtrace(cpumask_of(cpu), false);
-	return true;
+	return arch_trigger_cpumask_backtrace(cpumask_of(cpu), false);
 }
 
 /* generic implementation */
-- 
2.40.0.634.g4ca3ef3211-goog