[PATCH 6.1 v1] RISC-V: fix lock splat in riscv_cpufeature_patch_func()

[Conor Dooley <conor@kernel.org>]

From: Conor Dooley <conor.dooley@microchip.com>

Guenter reported a lockdep splat that appears to have been present for a
while in v6.1.y & the backports of the riscv_patch_in_stop_machine dance
did nothing to help here, as the lock is not being taken when
patch_text_nosync() is called in riscv_cpufeature_patch_func().
Add the lock/unlock; elide the splat.

Fixes: c15ac4fd60d5 ("riscv/ftrace: Add dynamic function tracer support")
Reported-by: Guenter Roeck <linux@roeck-us.net>
cc: stable@vger.kernel.org
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/kernel/cpufeature.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 694267d1fe81..fd1238df6149 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -9,6 +9,7 @@
 #include <linux/bitmap.h>
 #include <linux/ctype.h>
 #include <linux/libfdt.h>
+#include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <asm/alternative.h>
@@ -316,8 +317,11 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
 		}
 
 		tmp = (1U << alt->errata_id);
-		if (cpu_req_feature & tmp)
+		if (cpu_req_feature & tmp) {
+			mutex_lock(&text_mutex);
 			patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
+			mutex_unlock(&text_mutex);
+		}
 	}
 }
 #endif
-- 
2.39.2