linux-kernel - [PATCH v2 1/2] printk: introduce dump_stack

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Date:   Thu,  6 May 2021 12:54:04 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     akpm@...ux-foundation.org, pmladek@...e.com, mingo@...nel.org
Cc:     bo.he@...el.com, yanmin_zhang@...ux.intel.com,
        psodagud@...cinc.com, dvyukov@...gle.com, elver@...gle.com,
        linux-kernel@...r.kernel.org, ryabinin.a.a@...il.com,
        Alexander Potapenko <glider@...gle.com>, he@...gle.com
Subject: [PATCH v2 1/2] printk: introduce dump_stack_lvl()

dump_stack() is used for many different cases, which may require a log
level consistent with other kernel messages surrounding the dump_stack()
call.
Without that, certain systems that are configured to ignore the default
level messages will miss stack traces in critical error reports.

This patch introduces dump_stack_lvl() that behaves similarly to
dump_stack(), but accepts a custom log level.
The old dump_stack() becomes equal to dump_stack_lvl(KERN_DEFAULT).

A somewhat similar patch has been proposed in 2012:
https://lore.kernel.org/lkml/1332493269.2359.9.camel@hebo/
, but wasn't merged.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Petr Mladek <pmladek@...e.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: he, bo <bo.he@...el.com>
Cc: Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Cc: Prasad Sodagudi <psodagud@...cinc.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Marco Elver <elver@...gle.com>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Alexander Potapenko <glider@...gle.com>

---

v2:
 -- export dump_stack_lvl() (spotted by Marco Elver)
---
 include/linux/printk.h |  1 +
 lib/dump_stack.c       | 20 +++++++++++++-------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index fe7eb2351610..abe274305d79 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -206,6 +206,7 @@ void __init setup_log_buf(int early);
 __printf(1, 2) void dump_stack_set_arch_desc(const char *fmt, ...);
 void dump_stack_print_info(const char *log_lvl);
 void show_regs_print_info(const char *log_lvl);
+extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold;
 extern asmlinkage void dump_stack(void) __cold;
 extern void printk_safe_flush(void);
 extern void printk_safe_flush_on_panic(void);
diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index f5a33b6f773f..586e3f2c6a15 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -73,10 +73,10 @@ void show_regs_print_info(const char *log_lvl)
 	dump_stack_print_info(log_lvl);
 }
 
-static void __dump_stack(void)
+static void __dump_stack(const char *log_lvl)
 {
-	dump_stack_print_info(KERN_DEFAULT);
-	show_stack(NULL, NULL, KERN_DEFAULT);
+	dump_stack_print_info(log_lvl);
+	show_stack(NULL, NULL, log_lvl);
 }
 
 /**
@@ -87,7 +87,7 @@ static void __dump_stack(void)
 #ifdef CONFIG_SMP
 static atomic_t dump_lock = ATOMIC_INIT(-1);
 
-asmlinkage __visible void dump_stack(void)
+asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
 {
 	unsigned long flags;
 	int was_locked;
@@ -117,7 +117,7 @@ asmlinkage __visible void dump_stack(void)
 		goto retry;
 	}
 
-	__dump_stack();
+	__dump_stack(log_lvl);
 
 	if (!was_locked)
 		atomic_set(&dump_lock, -1);
@@ -125,9 +125,15 @@ asmlinkage __visible void dump_stack(void)
 	local_irq_restore(flags);
 }
 #else
-asmlinkage __visible void dump_stack(void)
+asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
 {
-	__dump_stack();
+	__dump_stack(log_lvl);
 }
 #endif
+EXPORT_SYMBOL(dump_stack_lvl);
+
+asmlinkage __visible void dump_stack(void)
+{
+	dump_stack_lvl(KERN_DEFAULT);
+}
 EXPORT_SYMBOL(dump_stack);
-- 
2.31.1.527.g47e6f16901-goog