[patch 26/93] powerpc: add show_stack_loglvl()

From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, benh@kernel.crashing.org,
	dima@arista.com, linux-mm@kvack.org, mm-commits@vger.kernel.org,
	mpe@ellerman.id.au, paulus@samba.org,
	torvalds@linux-foundation.org
Subject: [patch 26/93] powerpc: add show_stack_loglvl()
Date: Mon, 08 Jun 2020 21:31:14 -0700	[thread overview]
Message-ID: <20200609043114.VET-IRl5c%akpm@linux-foundation.org> (raw)
In-Reply-To: <20200608212922.5b7fa74ca3f4e2444441b7f9@linux-foundation.org>

From: Dmitry Safonov <dima@arista.com>
Subject: powerpc: 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().

[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u

Link: http://lkml.kernel.org/r/20200418201944.482088-27-dima@arista.com
Signed-off-by: Dmitry Safonov <dima@arista.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/powerpc/kernel/process.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

--- a/arch/powerpc/kernel/process.c~powerpc-add-show_stack_loglvl
+++ a/arch/powerpc/kernel/process.c
@@ -2063,7 +2063,8 @@ unsigned long get_wchan(struct task_stru
 
 static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;
 
-void show_stack(struct task_struct *tsk, unsigned long *stack)
+void show_stack_loglvl(struct task_struct *tsk, unsigned long *stack,
+		       const char *loglvl)
 {
 	unsigned long sp, ip, lr, newsp;
 	int count = 0;
@@ -2088,7 +2089,7 @@ void show_stack(struct task_struct *tsk,
 	}
 
 	lr = 0;
-	printk("Call Trace:\n");
+	printk("%sCall Trace:\n", loglvl);
 	do {
 		if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD))
 			break;
@@ -2097,7 +2098,8 @@ void show_stack(struct task_struct *tsk,
 		newsp = stack[0];
 		ip = stack[STACK_FRAME_LR_SAVE];
 		if (!firstframe || ip != lr) {
-			printk("["REG"] ["REG"] %pS", sp, ip, (void *)ip);
+			printk("%s["REG"] ["REG"] %pS",
+				loglvl, sp, ip, (void *)ip);
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 			ret_addr = ftrace_graph_ret_addr(current,
 						&ftrace_idx, ip, stack);
@@ -2119,8 +2121,9 @@ void show_stack(struct task_struct *tsk,
 			struct pt_regs *regs = (struct pt_regs *)
 				(sp + STACK_FRAME_OVERHEAD);
 			lr = regs->link;
-			printk("--- interrupt: %lx at %pS\n    LR = %pS\n",
-			       regs->trap, (void *)regs->nip, (void *)lr);
+			printk("%s--- interrupt: %lx at %pS\n    LR = %pS\n",
+			       loglvl, regs->trap,
+			       (void *)regs->nip, (void *)lr);
 			firstframe = 1;
 		}
 
@@ -2130,6 +2133,11 @@ void show_stack(struct task_struct *tsk,
 	put_task_stack(tsk);
 }
 
+void show_stack(struct task_struct *tsk, unsigned long *stack)
+{
+	show_stack_loglvl(tsk, stack, KERN_DEFAULT);
+}
+
 #ifdef CONFIG_PPC64
 /* Called with hard IRQs off */
 void notrace __ppc64_runlatch_on(void)
_

