[PATCH 6.1 191/473] dev_printk: Add and use dev_no_printk()

Greg Kroah-Hartman
2024-06-06T14:15:11Z

From: Geert Uytterhoeven <geert+renesas@glider.be>

[ Upstream commit c26ec799042a3888935d59b599f33e41efedf5f8 ]

When printk-indexing is enabled, each dev_printk() invocation emits a
pi_entry structure. This is even true when the dev_printk() is
protected by an always-false check, as is typically the case for debug
messages: while the actual code to print the message is optimized out by
the compiler, the pi_entry structure is still emitted.

Avoid emitting pi_entry structures for unavailable dev_printk() kernel
messages by:
1. Introducing a dev_no_printk() helper, mimicked after the existing
no_printk() helper, which calls _dev_printk() instead of
dev_printk(),
2. Replacing all "if (0) dev_printk(...)" constructs by calls to the
new helper.

This reduces the size of an arm64 defconfig kernel with
CONFIG_PRINTK_INDEX=y by 957 KiB.

Fixes: ad7d61f159db7397 ("printk: index: Add indexing support to dev_printk")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/8583d54f1687c801c6cda8edddf2cf0344c6e883.1709127473.git.geert+renesas@glider.be
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/dev_printk.h | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/include/linux/dev_printk.h b/include/linux/dev_printk.h
index 8904063d4c9f0..65eec5be8ccb9 100644
--- a/include/linux/dev_printk.h
+++ b/include/linux/dev_printk.h
@@ -129,6 +129,16 @@ void _dev_info(const struct device *dev, const char *fmt, ...)
_dev_printk(level, dev, fmt, ##__VA_ARGS__); \
})

+/*
+ * Dummy dev_printk for disabled debugging statements to use whilst maintaining
+ * gcc's format checking.
+ */
+#define dev_no_printk(level, dev, fmt, ...) \
+ ({ \
+ if (0) \
+ _dev_printk(level, dev, fmt, ##__VA_ARGS__); \
+ })
+
/*
* #defines for all the dev_<level> macros to prefix with whatever
* possible use of #define dev_fmt(fmt) ...
@@ -158,10 +168,7 @@ void _dev_info(const struct device *dev, const char *fmt, ...)
dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
#else
#define dev_dbg(dev, fmt, ...) \
-({ \
- if (0) \
- dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
-})
+ dev_no_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
#endif

#ifdef CONFIG_PRINTK
@@ -247,20 +254,14 @@ do { \
} while (0)
#else
#define dev_dbg_ratelimited(dev, fmt, ...) \
-do { \
- if (0) \
- dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
-} while (0)
+ dev_no_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
#endif

#ifdef VERBOSE_DEBUG
#define dev_vdbg dev_dbg
#else
#define dev_vdbg(dev, fmt, ...) \
-({ \
- if (0) \
- dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
-})
+ dev_no_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
#endif

/*
--
2.43.0