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From: Dawei Li <dawei.li@shingroup.cn>
To: davem@davemloft.net,
	andreas@gaisler.com
Cc: sparclinux@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	sam@ravnborg.org,
	Dawei Li <dawei.li@shingroup.cn>
Subject: [PATCH v2 7/7] sparc/smp: Remove on-stack cpumask var
Date: Sat, 20 Apr 2024 13:15:47 +0800
Message-Id: <20240420051547.3681642-8-dawei.li@shingroup.cn>
In-Reply-To: <20240420051547.3681642-1-dawei.li@shingroup.cn>
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In general it's preferable to avoid placing cpumasks on the stack, as
for large values of NR_CPUS these can consume significant amounts of
stack space and make stack overflows more likely.

- Change prototype of sparc32_ipi_ops::cross_call() so that it takes
  const cpumask * arg and all its callers accordingly.

- As for all cross_call() implementations, divide cpumask_test_cpu() call
  into several sub calls to avoid on-stack cpumask var.

Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
---
 arch/sparc/include/asm/smp_32.h | 12 ++++++------
 arch/sparc/kernel/kernel.h      | 11 +++++++++++
 arch/sparc/kernel/leon_smp.c    | 11 ++++-------
 arch/sparc/kernel/sun4d_smp.c   | 10 ++++------
 arch/sparc/kernel/sun4m_smp.c   | 10 ++++------
 5 files changed, 29 insertions(+), 25 deletions(-)

diff --git a/arch/sparc/include/asm/smp_32.h b/arch/sparc/include/asm/smp_32.h
index 2cf7971d7f6c..9b6a166f6a57 100644
--- a/arch/sparc/include/asm/smp_32.h
+++ b/arch/sparc/include/asm/smp_32.h
@@ -54,7 +54,7 @@ void smp_bogo(struct seq_file *);
 void smp_info(struct seq_file *);
 
 struct sparc32_ipi_ops {
-	void (*cross_call)(void *func, cpumask_t mask, unsigned long arg1,
+	void (*cross_call)(void *func, const cpumask_t *mask, unsigned long arg1,
 			   unsigned long arg2, unsigned long arg3,
 			   unsigned long arg4);
 	void (*resched)(int cpu);
@@ -65,29 +65,29 @@ extern const struct sparc32_ipi_ops *sparc32_ipi_ops;
 
 static inline void xc0(void *func)
 {
-	sparc32_ipi_ops->cross_call(func, *cpu_online_mask, 0, 0, 0, 0);
+	sparc32_ipi_ops->cross_call(func, cpu_online_mask, 0, 0, 0, 0);
 }
 
 static inline void xc1(void *func, unsigned long arg1)
 {
-	sparc32_ipi_ops->cross_call(func, *cpu_online_mask, arg1, 0, 0, 0);
+	sparc32_ipi_ops->cross_call(func, cpu_online_mask, arg1, 0, 0, 0);
 }
 static inline void xc2(void *func, unsigned long arg1, unsigned long arg2)
 {
-	sparc32_ipi_ops->cross_call(func, *cpu_online_mask, arg1, arg2, 0, 0);
+	sparc32_ipi_ops->cross_call(func, cpu_online_mask, arg1, arg2, 0, 0);
 }
 
 static inline void xc3(void *func, unsigned long arg1, unsigned long arg2,
 		       unsigned long arg3)
 {
-	sparc32_ipi_ops->cross_call(func, *cpu_online_mask,
+	sparc32_ipi_ops->cross_call(func, cpu_online_mask,
 				    arg1, arg2, arg3, 0);
 }
 
 static inline void xc4(void *func, unsigned long arg1, unsigned long arg2,
 		       unsigned long arg3, unsigned long arg4)
 {
-	sparc32_ipi_ops->cross_call(func, *cpu_online_mask,
+	sparc32_ipi_ops->cross_call(func, cpu_online_mask,
 				    arg1, arg2, arg3, arg4);
 }
 
diff --git a/arch/sparc/kernel/kernel.h b/arch/sparc/kernel/kernel.h
index a8fb7c0bf053..36747e8f7e36 100644
--- a/arch/sparc/kernel/kernel.h
+++ b/arch/sparc/kernel/kernel.h
@@ -4,6 +4,7 @@
 
 #include <linux/interrupt.h>
 #include <linux/ftrace.h>
+#include <linux/smp.h>
 
 #include <asm/traps.h>
 #include <asm/head.h>
@@ -75,6 +76,16 @@ int sparc32_classify_syscall(unsigned int syscall);
 #endif
 
 #ifdef CONFIG_SPARC32
+
+#ifdef CONFIG_SMP
+static inline bool cpu_for_ipi(const cpumask_t *mask, unsigned int cpu)
+{
+	return cpumask_test_cpu(cpu, mask) &&
+	       cpumask_test_cpu(cpu, cpu_online_mask) &&
+	       cpu != smp_processor_id();
+}
+#endif /* CONFIG_SMP */
+
 /* setup_32.c */
 struct linux_romvec;
 void sparc32_start_kernel(struct linux_romvec *rp);
diff --git a/arch/sparc/kernel/leon_smp.c b/arch/sparc/kernel/leon_smp.c
index 1ee393abc463..291884c8d82a 100644
--- a/arch/sparc/kernel/leon_smp.c
+++ b/arch/sparc/kernel/leon_smp.c
@@ -372,7 +372,7 @@ static struct smp_funcall {
 static DEFINE_SPINLOCK(cross_call_lock);
 
 /* Cross calls must be serialized, at least currently. */
-static void leon_cross_call(void *func, cpumask_t mask, unsigned long arg1,
+static void leon_cross_call(void *func, const cpumask_t *mask, unsigned long arg1,
 			    unsigned long arg2, unsigned long arg3,
 			    unsigned long arg4)
 {
@@ -403,14 +403,11 @@ static void leon_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 		{
 			register int i;
 
-			cpumask_clear_cpu(smp_processor_id(), &mask);
-			cpumask_and(&mask, cpu_online_mask, &mask);
 			for (i = 0; i <= high; i++) {
-				if (cpumask_test_cpu(i, &mask)) {
+				if (cpu_for_ipi(mask, i)) {
 					ccall_info.processors_in[i] = 0;
 					ccall_info.processors_out[i] = 0;
 					leon_send_ipi(i, LEON3_IRQ_CROSS_CALL);
-
 				}
 			}
 		}
@@ -420,7 +417,7 @@ static void leon_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 
 			i = 0;
 			do {
-				if (!cpumask_test_cpu(i, &mask))
+				if (!cpu_for_ipi(mask, i))
 					continue;
 
 				while (!ccall_info.processors_in[i])
@@ -429,7 +426,7 @@ static void leon_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 
 			i = 0;
 			do {
-				if (!cpumask_test_cpu(i, &mask))
+				if (!cpu_for_ipi(mask, i))
 					continue;
 
 				while (!ccall_info.processors_out[i])
diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
index 9a62a5cf3337..7dc57ca05728 100644
--- a/arch/sparc/kernel/sun4d_smp.c
+++ b/arch/sparc/kernel/sun4d_smp.c
@@ -281,7 +281,7 @@ static struct smp_funcall {
 static DEFINE_SPINLOCK(cross_call_lock);
 
 /* Cross calls must be serialized, at least currently. */
-static void sun4d_cross_call(void *func, cpumask_t mask, unsigned long arg1,
+static void sun4d_cross_call(void *func, const cpumask_t *mask, unsigned long arg1,
 			     unsigned long arg2, unsigned long arg3,
 			     unsigned long arg4)
 {
@@ -315,10 +315,8 @@ static void sun4d_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 		{
 			register int i;
 
-			cpumask_clear_cpu(smp_processor_id(), &mask);
-			cpumask_and(&mask, cpu_online_mask, &mask);
 			for (i = 0; i <= high; i++) {
-				if (cpumask_test_cpu(i, &mask)) {
+				if (cpu_for_ipi(mask, i)) {
 					ccall_info.processors_in[i] = 0;
 					ccall_info.processors_out[i] = 0;
 					sun4d_send_ipi(i, IRQ_CROSS_CALL);
@@ -331,7 +329,7 @@ static void sun4d_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 
 			i = 0;
 			do {
-				if (!cpumask_test_cpu(i, &mask))
+				if (!cpu_for_ipi(mask, i))
 					continue;
 				while (!ccall_info.processors_in[i])
 					barrier();
@@ -339,7 +337,7 @@ static void sun4d_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 
 			i = 0;
 			do {
-				if (!cpumask_test_cpu(i, &mask))
+				if (!cpu_for_ipi(mask, i))
 					continue;
 				while (!ccall_info.processors_out[i])
 					barrier();
diff --git a/arch/sparc/kernel/sun4m_smp.c b/arch/sparc/kernel/sun4m_smp.c
index 056df034e79e..3f43f64e3489 100644
--- a/arch/sparc/kernel/sun4m_smp.c
+++ b/arch/sparc/kernel/sun4m_smp.c
@@ -170,7 +170,7 @@ static struct smp_funcall {
 static DEFINE_SPINLOCK(cross_call_lock);
 
 /* Cross calls must be serialized, at least currently. */
-static void sun4m_cross_call(void *func, cpumask_t mask, unsigned long arg1,
+static void sun4m_cross_call(void *func, const cpumask_t *mask, unsigned long arg1,
 			     unsigned long arg2, unsigned long arg3,
 			     unsigned long arg4)
 {
@@ -191,10 +191,8 @@ static void sun4m_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 		{
 			register int i;
 
-			cpumask_clear_cpu(smp_processor_id(), &mask);
-			cpumask_and(&mask, cpu_online_mask, &mask);
 			for (i = 0; i < ncpus; i++) {
-				if (cpumask_test_cpu(i, &mask)) {
+				if (cpu_for_ipi(mask, i)) {
 					ccall_info.processors_in[i] = 0;
 					ccall_info.processors_out[i] = 0;
 					sun4m_send_ipi(i, IRQ_CROSS_CALL);
@@ -210,7 +208,7 @@ static void sun4m_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 
 			i = 0;
 			do {
-				if (!cpumask_test_cpu(i, &mask))
+				if (!cpu_for_ipi(mask, i))
 					continue;
 				while (!ccall_info.processors_in[i])
 					barrier();
@@ -218,7 +216,7 @@ static void sun4m_cross_call(void *func, cpumask_t mask, unsigned long arg1,
 
 			i = 0;
 			do {
-				if (!cpumask_test_cpu(i, &mask))
+				if (!cpu_for_ipi(mask, i))
 					continue;
 				while (!ccall_info.processors_out[i])
 					barrier();
-- 
2.27.0