linux-kernel - [PATCH] xtensa: improve stack dumping

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Message-Id: <20191106181617.1832-1-jcmvbkbc@gmail.com>
Date:   Wed,  6 Nov 2019 10:16:17 -0800
From:   Max Filippov <jcmvbkbc@...il.com>
To:     linux-xtensa@...ux-xtensa.org
Cc:     Chris Zankel <chris@...kel.net>, linux-kernel@...r.kernel.org,
        Dmitry Safonov <dima@...sta.com>,
        Petr Mladek <pmladek@...e.com>,
        Max Filippov <jcmvbkbc@...il.com>
Subject: [PATCH] xtensa: improve stack dumping

Collect whole stack dump lines in a buffer and print the whole buffer
when it's ready with pr_info instead of pr_cont. This makes stack dump
lines consistent in SMP case and relies less on pr_cont/printk
differences related to timestamps.
Make size of stack dump configurable.
Drop extra newline output in show_trace as its output format does not
depend on CONFIG_KALLSYMS.

Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
---
 arch/xtensa/Kconfig.debug  |  7 +++++++
 arch/xtensa/kernel/traps.c | 12 ++++++------
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/xtensa/Kconfig.debug b/arch/xtensa/Kconfig.debug
index 39de98e20018..83cc8d12fa0e 100644
--- a/arch/xtensa/Kconfig.debug
+++ b/arch/xtensa/Kconfig.debug
@@ -31,3 +31,10 @@ config S32C1I_SELFTEST
 	  It is easy to make wrong hardware configuration, this test should catch it early.
 
 	  Say 'N' on stable hardware.
+
+config PRINT_STACK_DEPTH
+	int "Stack depth to print" if DEBUG_KERNEL
+	default 64
+	help
+	  This option allows you to set the stack depth that the kernel
+	  prints in stack traces.
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 4a6c495ce9b6..b0c952652c73 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -491,17 +491,15 @@ void show_trace(struct task_struct *task, unsigned long *sp)
 
 	pr_info("Call Trace:\n");
 	walk_stackframe(sp, show_trace_cb, NULL);
-#ifndef CONFIG_KALLSYMS
-	pr_cont("\n");
-#endif
 }
 
-static int kstack_depth_to_print = 24;
+static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;
 
 void show_stack(struct task_struct *task, unsigned long *sp)
 {
 	int i = 0;
 	unsigned long *stack;
+	char buf[9 * 8 + 1];
 
 	if (!sp)
 		sp = stack_pointer(task);
@@ -512,10 +510,12 @@ void show_stack(struct task_struct *task, unsigned long *sp)
 	for (i = 0; i < kstack_depth_to_print; i++) {
 		if (kstack_end(sp))
 			break;
-		pr_cont(" %08lx", *sp++);
+		sprintf(buf + (i % 8) * 9, " %08lx", *sp++);
 		if (i % 8 == 7)
-			pr_cont("\n");
+			pr_info("%s\n", buf);
 	}
+	if (i % 8)
+		pr_info("%s\n", buf);
 	show_trace(task, stack);
 }
 
-- 
2.20.1