linux-kernel - [PATCH v2] PM: fix dynamic debug within pm_pr

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Message-ID: <20220312043624.40732-1-dacohen@pm.me>
Date:   Sat, 12 Mar 2022 04:36:45 +0000
From:   David Cohen <dacohen@...me>
To:     rafael@...nel.org, pavel@....cz, len.brown@...el.com
Cc:     David Cohen <dacohen@...me>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] PM: fix dynamic debug within pm_pr_debug()

Currently, pm_pr_debug() and pm_deferred_pr_debug() use __pm_pr_debug()
to filter pm debug messages based on pm_debug_messages_on flag.
According to __pm_pr_debug() implementation, pm_deferred_pr_debug()
indirectly calls printk_deferred() within __pm_pr_debug() which doesn't
support dynamic debug, but pm_pr_debug() indirectly calls pr_debug()
which does support dynamic debug.

The problem is if we enable/disable dynamic debug inside __pm_pr_debug()
it will affect all pm_pr_debug() calls at once, so we can't individually
control them.

This patch changes __pm_pr_debug() implementation into macros to make
pr_debug() to be directly called by all pm_pr_debug() cases. As a direct
side effect all pm_pr_debug() can be individually controlled by dynamic
debug feature.

Signed-off-by: David Cohen <dacohen@...me>
---
 include/linux/suspend.h | 19 +++++++++++++++----
 kernel/power/main.c     | 29 -----------------------------
 2 files changed, 15 insertions(+), 33 deletions(-)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 300273ff40cc..d727d3c867e3 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -542,22 +542,33 @@ static inline void unlock_system_sleep(void) {}
 #ifdef CONFIG_PM_SLEEP_DEBUG
 extern bool pm_print_times_enabled;
 extern bool pm_debug_messages_on;
-extern __printf(2, 3) void __pm_pr_dbg(bool defer, const char *fmt, ...);
+#define __pm_pr_dbg(fmt, ...)					\
+	do {							\
+		if (pm_debug_messages_on)			\
+			pr_debug("PM: " fmt, ##__VA_ARGS__);	\
+	} while(0)
+#define __pm_deferred_pr_dbg(fmt, ...)				\
+	do {							\
+		if (pm_debug_messages_on)			\
+			printk_deferred(KERN_DEBUG "PM: " fmt, ##__VA_ARGS__);	\
+	} while(0)
 #else
 #define pm_print_times_enabled	(false)
 #define pm_debug_messages_on	(false)

 #include <linux/printk.h>

-#define __pm_pr_dbg(defer, fmt, ...) \
+#define __pm_pr_dbg(fmt, ...) \
+	no_printk(KERN_DEBUG fmt, ##__VA_ARGS__)
+#define __pm_deferred_pr_dbg(fmt, ...) \
 	no_printk(KERN_DEBUG fmt, ##__VA_ARGS__)
 #endif

 #define pm_pr_dbg(fmt, ...) \
-	__pm_pr_dbg(false, fmt, ##__VA_ARGS__)
+	__pm_pr_dbg(fmt, ##__VA_ARGS__)

 #define pm_deferred_pr_dbg(fmt, ...) \
-	__pm_pr_dbg(true, fmt, ##__VA_ARGS__)
+	__pm_deferred_pr_dbg(fmt, ##__VA_ARGS__)

 #ifdef CONFIG_PM_AUTOSLEEP

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 7e646079fbeb..5242bf2ee469 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -545,35 +545,6 @@ static int __init pm_debug_messages_setup(char *str)
 }
 __setup("pm_debug_messages", pm_debug_messages_setup);

-/**
- * __pm_pr_dbg - Print a suspend debug message to the kernel log.
- * @defer: Whether or not to use printk_deferred() to print the message.
- * @fmt: Message format.
- *
- * The message will be emitted if enabled through the pm_debug_messages
- * sysfs attribute.
- */
-void __pm_pr_dbg(bool defer, const char *fmt, ...)
-{
-	struct va_format vaf;
-	va_list args;
-
-	if (!pm_debug_messages_on)
-		return;
-
-	va_start(args, fmt);
-
-	vaf.fmt = fmt;
-	vaf.va = &args;
-
-	if (defer)
-		printk_deferred(KERN_DEBUG "PM: %pV", &vaf);
-	else
-		printk(KERN_DEBUG "PM: %pV", &vaf);
-
-	va_end(args);
-}
-
 #else /* !CONFIG_PM_SLEEP_DEBUG */
 static inline void pm_print_times_init(void) {}
 #endif /* CONFIG_PM_SLEEP_DEBUG */
--
2.35.1