linux-kernel - [PATCHv2 23/50] nios2: Add show_stack

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Message-Id: <20200316143916.195608-24-dima@arista.com>
Date:   Mon, 16 Mar 2020 14:38:49 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Dmitry Safonov <dima@...sta.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Ley Foon Tan <lftan@...era.com>,
        nios2-dev@...ts.rocketboards.org
Subject: [PATCHv2 23/50] nios2: Add show_stack_loglvl()

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Introduce show_stack_loglvl(), that eventually will substitute
show_stack().

Cc: Ley Foon Tan <lftan@...era.com>
Cc: nios2-dev@...ts.rocketboards.org
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 arch/nios2/kernel/traps.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/nios2/kernel/traps.c b/arch/nios2/kernel/traps.c
index 486db793923c..08071caa9b36 100644
--- a/arch/nios2/kernel/traps.c
+++ b/arch/nios2/kernel/traps.c
@@ -52,12 +52,14 @@ void _exception(int signo, struct pt_regs *regs, int code, unsigned long addr)
 }
 
 /*
- * The show_stack is an external API which we do not use ourselves.
+ * The show_stack(), show_stack_loglvl() are external API
+ * which we do not use ourselves.
  */
 
 int kstack_depth_to_print = 48;
 
-void show_stack(struct task_struct *task, unsigned long *stack)
+void show_stack_loglvl(struct task_struct *task, unsigned long *stack,
+		       const char *loglvl)
 {
 	unsigned long *endstack, addr;
 	int i;
@@ -72,16 +74,16 @@ void show_stack(struct task_struct *task, unsigned long *stack)
 	addr = (unsigned long) stack;
 	endstack = (unsigned long *) PAGE_ALIGN(addr);
 
-	pr_emerg("Stack from %08lx:", (unsigned long)stack);
+	printk("%sStack from %08lx:", loglvl, (unsigned long)stack);
 	for (i = 0; i < kstack_depth_to_print; i++) {
 		if (stack + 1 > endstack)
 			break;
 		if (i % 8 == 0)
-			pr_emerg("\n       ");
-		pr_emerg(" %08lx", *stack++);
+			printk("%s\n       ", loglvl);
+		printk("%s %08lx", loglvl, *stack++);
 	}
 
-	pr_emerg("\nCall Trace:");
+	printk("%s\nCall Trace:", loglvl);
 	i = 0;
 	while (stack + 1 <= endstack) {
 		addr = *stack++;
@@ -97,11 +99,16 @@ void show_stack(struct task_struct *task, unsigned long *stack)
 		     (addr <= (unsigned long) _etext))) {
 			if (i % 4 == 0)
 				pr_emerg("\n       ");
-			pr_emerg(" [<%08lx>]", addr);
+			printk("%s [<%08lx>]", loglvl, addr);
 			i++;
 		}
 	}
-	pr_emerg("\n");
+	printk("%s\n", loglvl);
+}
+
+void show_stack(struct task_struct *task, unsigned long *stack)
+{
+	show_stack_loglvl(task, stack, KERN_EMERG);
 }
 
 void __init trap_init(void)
-- 
2.25.1