riscv: Use text_mutex instead of patch_lock

We don't need the additional lock protection when patching the text.

There are two patching interfaces here:
 - patch_text: patch code and always synchronize with stop_machine()
 - patch_text_nosync: patch code without synchronization, it's caller's
                      responsibility to synchronize all CPUs if needed.

For the first one, stop_machine() is protected by its own mutex, and
also the irq is already disabled here.

For the second one, in risc-v real case now, it would be used to ftrace
patching the mcount function, since it already running under
kstop_machine(), no other thread will run, so we could use text_mutex
on ftrace side.

Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index fb1e2b8fe254..08396614d6f4 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -7,10 +7,23 @@
 
 #include <linux/ftrace.h>
 #include <linux/uaccess.h>
+#include <linux/memory.h>
 #include <asm/cacheflush.h>
 #include <asm/patch.h>
 
 #ifdef CONFIG_DYNAMIC_FTRACE
+int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
+{
+	mutex_lock(&text_mutex);
+	return 0;
+}
+
+int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
+{
+	mutex_unlock(&text_mutex);
+	return 0;
+}
+
 static int ftrace_check_current_call(unsigned long hook_pos,
 				     unsigned int *expected)
 {