linux-kernel - [PATCHv2 27/50] riscv: Add show_stack

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Date:   Mon, 16 Mar 2020 14:38:53 +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>,
        Albert Ou <aou@...s.berkeley.edu>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv@...ts.infradead.org
Subject: [PATCHv2 27/50] riscv: 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: Albert Ou <aou@...s.berkeley.edu>
Cc: Palmer Dabbelt <palmer@...belt.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>
Cc: linux-riscv@...ts.infradead.org
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 arch/riscv/kernel/stacktrace.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index a76892b48fff..5b414ba9848b 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -98,16 +98,23 @@ static void notrace walk_stackframe(struct task_struct *task,
 
 static bool print_trace_address(unsigned long pc, void *arg)
 {
-	print_ip_sym(KERN_DEFAULT, pc);
+	const char *loglvl = arg;
+
+	print_ip_sym(loglvl, pc);
 	return false;
 }
 
-void show_stack(struct task_struct *task, unsigned long *sp)
+void show_stack_loglvl(struct task_struct *task, unsigned long *sp,
+		       const char *loglvl)
 {
 	pr_cont("Call Trace:\n");
-	walk_stackframe(task, NULL, print_trace_address, NULL);
+	walk_stackframe(task, NULL, print_trace_address, (void *)loglvl);
 }
 
+void show_stack(struct task_struct *task, unsigned long *sp)
+{
+	show_stack_loglvl(task, sp, KERN_DEFAULT);
+}
 
 static bool save_wchan(unsigned long pc, void *arg)
 {
-- 
2.25.1