[PATCH] Fix printk levels for panic, softlockup, etc.

* [PATCH] Fix printk levels for panic, softlockup, etc.
@ 2012-01-26 13:55 Prarit Bhargava
  2012-01-26 21:43 ` [tip:core/urgent] bugs, x86: Fix printk levels for panic, softlockups and stack dumps tip-bot for Prarit Bhargava
  0 siblings, 1 reply; 2+ messages in thread
From: Prarit Bhargava @ 2012-01-26 13:55 UTC (permalink / raw)
  To: linux-kernel; +Cc: Prarit Bhargava, dzickus, x86

rsyslog will display KERN_EMERG messages on a connected terminal.  However,
these messages are useless/undecipherable for a general user.

For example, after a softlockup,

Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ...
kernel:Stack:

Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ...
kernel:Call Trace:

Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ...
kernel:Code: ff ff a8 08 75 25 31 d2 48 8d 86 38 e0 ff ff 48 89 d1 0f 01 c8 0f ae f0 48 8b 86 38 e0 ff ff a8 08 75 08 b1 01 4c 89 e0 0f 01 c9 <e8> ea 69 dd ff 4c 29 e8 48 89 c7 e8 0f bc da ff 49 89 c4 49 89

This happens because the printk levels for these messages are incorrect.
Only an informational message should be displayed on a terminal.

I modified the printk levels for various messages in the kernel and tested
the output by using the drivers/misc/lkdtm.c kernel modules (ie, softlockups,
panics, hard lockups, etc.) and confirmed that the console output was still
the same and that the output to the terminals was correct.

For example, in the case of a softlockup we know see

Message from syslogd@intel-s3e37-04 at Jan 25 10:18:06 ...
BUG: soft lockup - CPU4 stuck for 60s!

instead of the above confusing messages.

AFAICT, the messages no longer have to be KERN_EMERG.  In the most important
case of a panic we set console_verbose().  As for the other less severe
cases the correct data is output to the console and /var/log/messages.

P.

-----8<-----
Adjust printk levels for panic, softlockup, etc, messages in the kernel.

Successfully tested by me using the drivers/misc/lkdtm.c module.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: dzickus@redhat.com
Cc: x86@kernel.org

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
---
 arch/x86/kernel/dumpstack.c    |    3 ++-
 arch/x86/kernel/dumpstack_64.c |    6 +++---
 arch/x86/mm/fault.c            |    4 ++--
 kernel/watchdog.c              |    2 +-
 lib/bug.c                      |    2 +-
 5 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 1aae78f..4025fe4 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -252,7 +252,8 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
 	unsigned short ss;
 	unsigned long sp;
 #endif
-	printk(KERN_EMERG "%s: %04lx [#%d] ", str, err & 0xffff, ++die_counter);
+	printk(KERN_DEFAULT
+	       "%s: %04lx [#%d] ", str, err & 0xffff, ++die_counter);
 #ifdef CONFIG_PREEMPT
 	printk("PREEMPT ");
 #endif
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 6d728d9..42b2bca 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -269,11 +269,11 @@ void show_registers(struct pt_regs *regs)
 		unsigned char c;
 		u8 *ip;
 
-		printk(KERN_EMERG "Stack:\n");
+		printk(KERN_DEFAULT "Stack:\n");
 		show_stack_log_lvl(NULL, regs, (unsigned long *)sp,
-				   0, KERN_EMERG);
+				   0, KERN_DEFAULT);
 
-		printk(KERN_EMERG "Code: ");
+		printk(KERN_DEFAULT "Code: ");
 
 		ip = (u8 *)regs->ip - code_prologue;
 		if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) {
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9d74824..f0b4caf 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -673,7 +673,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 
 	stackend = end_of_stack(tsk);
 	if (tsk != &init_task && *stackend != STACK_END_MAGIC)
-		printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
+		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
 
 	tsk->thread.cr2		= address;
 	tsk->thread.trap_no	= 14;
@@ -684,7 +684,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 		sig = 0;
 
 	/* Executive summary in case the body of the oops scrolled away */
-	printk(KERN_EMERG "CR2: %016lx\n", address);
+	printk(KERN_DEFAULT "CR2: %016lx\n", address);
 
 	oops_end(flags, regs, sig);
 }
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 1d7bca7..d117262 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -296,7 +296,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 		if (__this_cpu_read(soft_watchdog_warn) == true)
 			return HRTIMER_RESTART;
 
-		printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
+		printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 			smp_processor_id(), duration,
 			current->comm, task_pid_nr(current));
 		print_modules();
diff --git a/lib/bug.c b/lib/bug.c
index 1955209..a28c141 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -169,7 +169,7 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 		return BUG_TRAP_TYPE_WARN;
 	}
 
-	printk(KERN_EMERG "------------[ cut here ]------------\n");
+	printk(KERN_DEFAULT "------------[ cut here ]------------\n");
 
 	if (file)
 		printk(KERN_CRIT "kernel BUG at %s:%u!\n",
-- 
1.7.1


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