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: Prarit 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: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 1aae78f775fc18e4f01b2ed568a1934e2de6dd31..4025fe4f928f6f4cb2ddcfc0233197e9e0b3ad44 100644 (file)
--- 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 6d728d9284bd0e3b94213206bd93af5afbfb7912..42b2bca0b72ca6aa14e01891cc3903d4d1a27cba 100644 (file)
--- 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 9d74824a708dcdd1cd3b0e6ce4798e79fbbf1c01..f0b4caf85c1a8687496b863745f11838a4d430b8 100644 (file)
--- 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 1d7bca7f4f527c2f25b741da9fc914980a0c43bb..d117262deba305400ba768b1f7cecc945f3faba8 100644 (file)
--- 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 19552096d16b06bd2dac2a9b10212e482a4d0da3..a28c1415357cac9d30fc09195652fbfd099bc421 100644 (file)
--- 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",