ACPI: add dynamic_debug support

Commit 1a699476e258 ("ACPI / hotplug / PCI: Hotplug notifications
from acpi_bus_notify()") added debug messages for a few common
events. These debug messages are unconditionally enabled if
CONFIG_DYNAMIC_DEBUG is defined, contrary to the documented
meaning, making the ACPI system spew lots of unwanted noise on
any kernel with dynamic debugging.

The bug was introduced by commit fbfddae69657 ("ACPI: Add
acpi_handle_<level>() interfaces"), which added the
CONFIG_DYNAMIC_DEBUG dependency without respecting its meaning.

Fix by adding real support for dynamic_debug.

Fixes: fbfddae69657 ("ACPI: Add acpi_handle_<level>() interfaces")
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/utils.c

@@ -30,6 +30,7 @@
 #include <linux/types.h>
 #include <linux/hardirq.h>
 #include <linux/acpi.h>
+#include <linux/dynamic_debug.h>
 
 #include "internal.h"
 
@@ -456,6 +457,24 @@ acpi_evaluate_ost(acpi_handle handle, u32 source_event, u32 status_code,
 }
 EXPORT_SYMBOL(acpi_evaluate_ost);
 
+/**
+ * acpi_handle_path: Return the object path of handle
+ *
+ * Caller must free the returned buffer
+ */
+static char *acpi_handle_path(acpi_handle handle)
+{
+	struct acpi_buffer buffer = {
+		.length = ACPI_ALLOCATE_BUFFER,
+		.pointer = NULL
+	};
+
+	if (in_interrupt() ||
+	    acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer) != AE_OK)
+		return NULL;
+	return buffer.pointer;
+}
+
 /**
  * acpi_handle_printk: Print message with ACPI prefix and object path
  *
@@ -469,29 +488,50 @@ acpi_handle_printk(const char *level, acpi_handle handle, const char *fmt, ...)
 {
 	struct va_format vaf;
 	va_list args;
-	struct acpi_buffer buffer = {
-		.length = ACPI_ALLOCATE_BUFFER,
-		.pointer = NULL
-	};
 	const char *path;
 
 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	if (in_interrupt() ||
-	    acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer) != AE_OK)
-		path = "<n/a>";
-	else
-		path = buffer.pointer;
-
-	printk("%sACPI: %s: %pV", level, path, &vaf);
+	path = acpi_handle_path(handle);
+	printk("%sACPI: %s: %pV", level, path ? path : "<n/a>" , &vaf);
 
 	va_end(args);
-	kfree(buffer.pointer);
+	kfree(path);
 }
 EXPORT_SYMBOL(acpi_handle_printk);
 
+#if defined(CONFIG_DYNAMIC_DEBUG)
+/**
+ * __acpi_handle_debug: pr_debug with ACPI prefix and object path
+ *
+ * This function is called through acpi_handle_debug macro and debug
+ * prints a message with ACPI prefix and object path. This function
+ * acquires the global namespace mutex to obtain an object path.  In
+ * interrupt context, it shows the object path as <n/a>.
+ */
+void
+__acpi_handle_debug(struct _ddebug *descriptor, acpi_handle handle,
+		    const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+	const char *path;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	path = acpi_handle_path(handle);
+	__dynamic_pr_debug(descriptor, "ACPI: %s: %pV", path ? path : "<n/a>", &vaf);
+
+	va_end(args);
+	kfree(path);
+}
+EXPORT_SYMBOL(__acpi_handle_debug);
+#endif
+
 /**
  * acpi_has_method: Check whether @handle has a method named @name
  * @handle: ACPI device handle

include/linux/acpi.h

@@ -37,6 +37,7 @@
 
 #include <linux/list.h>
 #include <linux/mod_devicetable.h>
+#include <linux/dynamic_debug.h>
 
 #include <acpi/acpi.h>
 #include <acpi/acpi_bus.h>
@@ -589,6 +590,14 @@ static inline __printf(3, 4) void
 acpi_handle_printk(const char *level, void *handle, const char *fmt, ...) {}
 #endif	/* !CONFIG_ACPI */
 
+#if defined(CONFIG_ACPI) && defined(CONFIG_DYNAMIC_DEBUG)
+__printf(3, 4)
+void __acpi_handle_debug(struct _ddebug *descriptor, acpi_handle handle, const char *fmt, ...);
+#else
+#define __acpi_handle_debug(descriptor, handle, fmt, ...)		\
+	acpi_handle_printk(KERN_DEBUG, handle, fmt, ##__VA_ARGS__);
+#endif
+
 /*
  * acpi_handle_<level>: Print message with ACPI prefix and object path
  *
@@ -610,11 +619,19 @@ acpi_handle_printk(const char *level, void *handle, const char *fmt, ...) {}
 #define acpi_handle_info(handle, fmt, ...)				\
 	acpi_handle_printk(KERN_INFO, handle, fmt, ##__VA_ARGS__)
 
-/* REVISIT: Support CONFIG_DYNAMIC_DEBUG when necessary */
-#if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
+#if defined(DEBUG)
 #define acpi_handle_debug(handle, fmt, ...)				\
 	acpi_handle_printk(KERN_DEBUG, handle, fmt, ##__VA_ARGS__)
 #else
+#if defined(CONFIG_DYNAMIC_DEBUG)
+#define acpi_handle_debug(handle, fmt, ...)				\
+do {									\
+	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);			\
+	if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT))		\
+		__acpi_handle_debug(&descriptor, handle, pr_fmt(fmt),	\
+				##__VA_ARGS__);				\
+} while (0)
+#else
 #define acpi_handle_debug(handle, fmt, ...)				\
 ({									\
 	if (0)								\
@@ -622,5 +639,6 @@ acpi_handle_printk(const char *level, void *handle, const char *fmt, ...) {}
 	0;								\
 })
 #endif
+#endif
 
 #endif	/*_LINUX_ACPI_H*/