ftrace: nmi update statistics

Impact: add more debug info to /debugfs/tracing/dyn_ftrace_total_info

This patch adds dynamic ftrace NMI update statistics to the
/debugfs/tracing/dyn_ftrace_total_info stat file.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 24 insertions, 2 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index fe5f859130b5..6685b0fc1b44 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -91,6 +91,19 @@ static int mod_code_write;
 static void *mod_code_ip;
 static void *mod_code_newcode;
 
+static int nmi_wait_count;
+static atomic_t nmi_update_count;
+
+int ftrace_arch_read_dyn_info(char *buf, int size)
+{
+        int r;
+
+        r = snprintf(buf, size, "%u %u",
+                     nmi_wait_count,
+                     atomic_read(&nmi_update_count));
+        return r;
+}
+
 static void ftrace_mod_code(void)
 {
         /*
@@ -109,8 +122,10 @@ void ftrace_nmi_enter(void)
         atomic_inc(&in_nmi);
         /* Must have in_nmi seen before reading write flag */
         smp_mb();
-        if (mod_code_write)
+        if (mod_code_write) {
                 ftrace_mod_code();
+                atomic_inc(&nmi_update_count);
+        }
 }
 
 void ftrace_nmi_exit(void)
@@ -122,8 +137,15 @@ void ftrace_nmi_exit(void)
 
 static void wait_for_nmi(void)
 {
-        while (atomic_read(&in_nmi))
+        int waited = 0;
+
+        while (atomic_read(&in_nmi)) {
+                waited = 1;
                 cpu_relax();
+        }
+
+        if (waited)
+                nmi_wait_count++;
 }
 
 static int