[PATCH V11 07/17] riscv: qspinlock: Introduce qspinlock param for command line

[guoren at kernel.org]

From: Guo Ren <guoren at linux.alibaba.com>

Allow cmdline to force the kernel to use queued_spinlock when
CONFIG_RISCV_COMBO_SPINLOCKS=y.

Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  2 ++
 arch/riscv/kernel/setup.c                       | 16 +++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 7dfb540c4f6c..61cacb8dfd0e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4693,6 +4693,8 @@
 			[KNL] Number of legacy pty's. Overwrites compiled-in
 			default number.
 
+	qspinlock	[RISCV] Force to use qspinlock or auto-detect spinlock.
+
 	qspinlock.numa_spinlock_threshold_ns=	[NUMA, PV_OPS]
 			Set the time threshold in nanoseconds for the
 			number of intra-node lock hand-offs before the
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index a447cf360a18..0f084f037651 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -270,6 +270,15 @@ static void __init parse_dtb(void)
 }
 
 #ifdef CONFIG_RISCV_COMBO_SPINLOCKS
+bool enable_qspinlock_key = false;
+static int __init queued_spinlock_setup(char *p)
+{
+	enable_qspinlock_key = true;
+
+	return 0;
+}
+early_param("qspinlock", queued_spinlock_setup);
+
 DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key);
 EXPORT_SYMBOL(combo_qspinlock_key);
 #endif
@@ -277,7 +286,12 @@ EXPORT_SYMBOL(combo_qspinlock_key);
 static void __init riscv_spinlock_init(void)
 {
 #ifdef CONFIG_RISCV_COMBO_SPINLOCKS
-	static_branch_disable(&combo_qspinlock_key);
+	if (!enable_qspinlock_key) {
+		static_branch_disable(&combo_qspinlock_key);
+		pr_info("Ticket spinlock: enabled\n");
+	} else {
+		pr_info("Queued spinlock: enabled\n");
+	}
 #endif
 }
 
-- 
2.36.1