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| author | Ingo Molnar <mingo@elte.hu> | 2007-10-16 23:26:08 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-17 08:42:47 -0700 |
| commit | 43581a10075492445f65234384210492ff333eba (patch) | |
| tree | 2bcec45ff17207f57f8c4f4744b22411d1aeae6c /kernel/softlockup.c | |
| parent | ad3b82795f3f6e641081790409a051312622f2a6 (diff) | |
| download | linux-43581a10075492445f65234384210492ff333eba.tar.gz linux-43581a10075492445f65234384210492ff333eba.tar.bz2 linux-43581a10075492445f65234384210492ff333eba.zip | |
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.
[satyam@infradead.org: fix warning]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/softlockup.c')
| -rw-r--r-- | kernel/softlockup.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/kernel/softlockup.c b/kernel/softlockup.c index e423b3a918fd..65839c54abf5 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); } /* |