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Commit b0f4c4b3 authored by Prarit Bhargava's avatar Prarit Bhargava Committed by Ingo Molnar
Browse files

bugs, x86: Fix printk levels for panic, softlockups and stack dumps 



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 we get:

 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 now see the much
more informative:

 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.

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

Signed-off-by: default avatarPrarit Bhargava <prarit@redhat.com>
Cc: dzickus@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1327586134-11926-1-git-send-email-prarit@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b64b223a

arch/x86/kernel/dumpstack.c

+2 −1
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/dumpstack_64.c

+3 −3
Original line number Diff line number Diff line
@@ -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)) {

arch/x86/mm/fault.c

+2 −2
Original line number Diff line number Diff line
@@ -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);

}

kernel/watchdog.c

+1 −1
Original line number Diff line number Diff line
@@ -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();

lib/bug.c

+1 −1
Original line number Diff line number Diff line
@@ -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",