Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=43581a10075492445f65234384210492ff333eba
Commit:     43581a10075492445f65234384210492ff333eba
Parent:     ad3b82795f3f6e641081790409a051312622f2a6
Author:     Ingo Molnar <[EMAIL PROTECTED]>
AuthorDate: Tue Oct 16 23:26:08 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Oct 17 08:42:47 2007 -0700

    softlockup: improve debug output
    
    Improve the debuggability of kernel lockups by enhancing the debug
    output of the softlockup detector: print the task that causes the lockup
    and try to print a more intelligent backtrace.
    
    The old format was:
    
      BUG: soft lockup detected on CPU#1!
       [<c0105e4a>] show_trace_log_lvl+0x19/0x2e
       [<c0105f43>] show_trace+0x12/0x14
       [<c0105f59>] dump_stack+0x14/0x16
       [<c015f6bc>] softlockup_tick+0xbe/0xd0
       [<c013457d>] run_local_timers+0x12/0x14
       [<c01346b8>] update_process_times+0x3e/0x63
       [<c0145fb8>] tick_sched_timer+0x7c/0xc0
       [<c0140a75>] hrtimer_interrupt+0x135/0x1ba
       [<c011bde7>] smp_apic_timer_interrupt+0x6e/0x80
       [<c0105aa3>] apic_timer_interrupt+0x33/0x38
       [<c0104f8a>] syscall_call+0x7/0xb
       =======================
    
    The new format is:
    
      BUG: soft lockup detected on CPU#1! [prctl:2363]
    
      Pid: 2363, comm:                prctl
      EIP: 0060:[<c013915f>] CPU: 1
      EIP is at sys_prctl+0x24/0x18c
       EFLAGS: 00000213    Not tainted  (2.6.22-cfs-v20 #26)
      EAX: 00000001 EBX: 000003e7 ECX: 00000001 EDX: f6df0000
      ESI: 000003e7 EDI: 000003e7 EBP: f6df0fb0 DS: 007b ES: 007b FS: 00d8
      CR0: 8005003b CR2: 4d8c3340 CR3: 3731d000 CR4: 000006d0
       [<c0105e4a>] show_trace_log_lvl+0x19/0x2e
       [<c0105f43>] show_trace+0x12/0x14
       [<c01040be>] show_regs+0x1ab/0x1b3
       [<c015f807>] softlockup_tick+0xef/0x108
       [<c013457d>] run_local_timers+0x12/0x14
       [<c01346b8>] update_process_times+0x3e/0x63
       [<c0145fcc>] tick_sched_timer+0x7c/0xc0
       [<c0140a89>] hrtimer_interrupt+0x135/0x1ba
       [<c011bde7>] smp_apic_timer_interrupt+0x6e/0x80
       [<c0105aa3>] apic_timer_interrupt+0x33/0x38
       [<c0104f8a>] syscall_call+0x7/0xb
       =======================
    
    Note that in the old format we only knew that some system call locked
    up, we didnt know _which_. With the new format we know that it's at a
    specific place in sys_prctl(). [which was where i created an artificial
    kernel lockup to test the new format.]
    
    This is also useful if the lockup happens in user-space - the user-space
    EIP (and other registers) will be printed too. (such a lockup would
    either suggest that the task was running at SCHED_FIFO:99 and looping
    for more than 10 seconds, or that the softlockup detector has a
    false-positive.)
    
    The task name is printed too first, just in case we dont manage to print
    a useful backtrace.
    
    [EMAIL PROTECTED]: fix warning]
    Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
    Signed-off-by: Satyam Sharma <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 kernel/softlockup.c |   20 +++++++++++++-------
 1 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index e423b3a..65839c5 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -15,6 +15,8 @@
 #include <linux/notifier.h>
 #include <linux/module.h>
 
+#include <asm/irq_regs.h>
+
 static DEFINE_SPINLOCK(print_lock);
 
 static DEFINE_PER_CPU(unsigned long, touch_timestamp);
@@ -72,6 +74,7 @@ void softlockup_tick(void)
        int this_cpu = smp_processor_id();
        unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
        unsigned long print_timestamp;
+       struct pt_regs *regs = get_irq_regs();
        unsigned long now;
 
        if (touch_timestamp == 0) {
@@ -101,15 +104,18 @@ void softlockup_tick(void)
                wake_up_process(per_cpu(watchdog_task, this_cpu));
 
        /* Warn about unreasonable 10+ seconds delays: */
-       if (now > (touch_timestamp + 10)) {
-               per_cpu(print_timestamp, this_cpu) = touch_timestamp;
+       if (now <= (touch_timestamp + 10))
+               return;
 
-               spin_lock(&print_lock);
-               printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n",
-                       this_cpu);
+       per_cpu(print_timestamp, this_cpu) = touch_timestamp;
+
+       spin_lock(&print_lock);
+       printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n", this_cpu);
+       if (regs)
+               show_regs(regs);
+       else
                dump_stack();
-               spin_unlock(&print_lock);
-       }
+       spin_unlock(&print_lock);
 }
 
 /*
-
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