dyndbg: avoid calling dyndbg_emit_prefix when it has no work

Wrap function in a static-inline one, which checks flags to avoid
calling the function unnecessarily.

And hoist its output-buffer initialization to the grand-caller, which
is already allocating the buffer on the stack, and can trivially
initialize it too.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20210504222235.1033685-2-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index a57ee75..dce631e 100644 (file)
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -32,6 +32,11 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_INCL_FUNCNAME   (1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO     (1<<3)
 #define _DPRINTK_FLAGS_INCL_TID                (1<<4)
+
+#define _DPRINTK_FLAGS_INCL_ANY                \
+       (_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
+        _DPRINTK_FLAGS_INCL_LINENO  | _DPRINTK_FLAGS_INCL_TID)
+
 #if defined DEBUG
 #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
 #else

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 921d0a6..3989204 100644 (file)
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -586,13 +586,11 @@ static int remaining(int wrote)
        return 0;
 }
 
-static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
+static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
 {
        int pos_after_tid;
        int pos = 0;
 
-       *buf = '\0';
-
        if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
                if (in_interrupt())
                        pos += snprintf(buf + pos, remaining(pos), "<intr> ");
@@ -618,11 +616,18 @@ static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
        return buf;
 }
 
+static inline char *dynamic_emit_prefix(struct _ddebug *desc, char *buf)
+{
+       if (unlikely(desc->flags & _DPRINTK_FLAGS_INCL_ANY))
+               return __dynamic_emit_prefix(desc, buf);
+       return buf;
+}
+
 void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
 {
        va_list args;
        struct va_format vaf;
-       char buf[PREFIX_SIZE];
+       char buf[PREFIX_SIZE] = "";
 
        BUG_ON(!descriptor);
        BUG_ON(!fmt);
@@ -655,7 +660,7 @@ void __dynamic_dev_dbg(struct _ddebug *descriptor,
        if (!dev) {
                printk(KERN_DEBUG "(NULL device *): %pV", &vaf);
        } else {
-               char buf[PREFIX_SIZE];
+               char buf[PREFIX_SIZE] = "";
 
                dev_printk_emit(LOGLEVEL_DEBUG, dev, "%s%s %s: %pV",
                                dynamic_emit_prefix(descriptor, buf),
@@ -684,7 +689,7 @@ void __dynamic_netdev_dbg(struct _ddebug *descriptor,
        vaf.va = &args;
 
        if (dev && dev->dev.parent) {
-               char buf[PREFIX_SIZE];
+               char buf[PREFIX_SIZE] = "";
 
                dev_printk_emit(LOGLEVEL_DEBUG, dev->dev.parent,
                                "%s%s %s %s%s: %pV",
@@ -720,7 +725,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
        vaf.va = &args;
 
        if (ibdev && ibdev->dev.parent) {
-               char buf[PREFIX_SIZE];
+               char buf[PREFIX_SIZE] = "";
 
                dev_printk_emit(LOGLEVEL_DEBUG, ibdev->dev.parent,
                                "%s%s %s %s: %pV",