csky/ftrace: Fixup ftrace_modify_code deadlock without CPU_HAS_ICACHE_INS

If ICACHE_INS is not supported, we use IPI to sync icache on each
core. But ftrace_modify_code is called from stop_machine from default
implementation of arch_ftrace_update_code and stop_machine callback
is irq_disabled. When you call ipi with irq_disabled, a deadlock will
happen.

We couldn't use icache_flush with irq_disabled, but startup make_nop
is specific case and it needn't ipi other cores.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/arch/csky/kernel/ftrace.c b/arch/csky/kernel/ftrace.c
index b4502cd2eabe..44628e3f7fa6 100644
--- a/arch/csky/kernel/ftrace.c
+++ b/arch/csky/kernel/ftrace.c
@@ -3,6 +3,7 @@
 
 #include <linux/ftrace.h>
 #include <linux/uaccess.h>
+#include <linux/stop_machine.h>
 #include <asm/cacheflush.h>
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -201,5 +202,35 @@ int ftrace_disable_ftrace_graph_caller(void)
 #endif /* CONFIG_DYNAMIC_FTRACE */
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
+#ifndef CONFIG_CPU_HAS_ICACHE_INS
+struct ftrace_modify_param {
+	int command;
+	atomic_t cpu_count;
+};
+
+static int __ftrace_modify_code(void *data)
+{
+	struct ftrace_modify_param *param = data;
+
+	if (atomic_inc_return(&param->cpu_count) == 1) {
+		ftrace_modify_all_code(param->command);
+		atomic_inc(&param->cpu_count);
+	} else {
+		while (atomic_read(&param->cpu_count) <= num_online_cpus())
+			cpu_relax();
+		local_icache_inv_all(NULL);
+	}
+
+	return 0;
+}
+
+void arch_ftrace_update_code(int command)
+{
+	struct ftrace_modify_param param = { command, ATOMIC_INIT(0) };
+
+	stop_machine(__ftrace_modify_code, &param, cpu_online_mask);
+}
+#endif
+
 /* _mcount is defined in abi's mcount.S */
 EXPORT_SYMBOL(_mcount);