The patch titled
softlockup: improve debug output
has been removed from the -mm tree. Its filename was
softlockup-improve-debug-output.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: softlockup: improve debug output
From: Ingo Molnar <mingo@xxxxxxx>
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@xxxxxxxxxxxxx: fix warning]
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Satyam Sharma <satyam@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/softlockup.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff -puN kernel/softlockup.c~softlockup-improve-debug-output kernel/softlockup.c
--- a/kernel/softlockup.c~softlockup-improve-debug-output
+++ a/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);
}
/*
_
Patches currently in -mm which might be from mingo@xxxxxxx are
origin.patch
git-acpi.patch
git-kvm.patch
net-dccp-fix-link-error-with-config_sysctl.patch
git-netdev-all.patch
fix-build-breakage-if-sysfs-fix.patch
git-x86.patch
hpet-force-enable-on-vt8235-37-chipsets.patch
i386-paravirt-boot-sequence.patch
workqueue-debug-flushing-deadlocks-with-lockdep.patch
workqueue-debug-work-related-deadlocks-with-lockdep.patch
lockdep-fix-mismatched-lockdep_depth-curr_chain_hash-checkpatch-fixes.patch
whitespace-fixes-time-syscalls.patch
whitespace-fixes-interval-timers.patch
whitespace-fixes-system-timers.patch
uninline-find_task_by_xxx-set-of-functions.patch
cpuset-sched_load_balance-flag.patch
cpuset-sched_load_balance-flag-fix.patch
cpuset-sched_load_balance-kmalloc-fix.patch
cpusets-decrustify-cpuset-mask-update-code.patch
cpusets-decrustify-cpuset-mask-update-code-checkpatch-fixes.patch
hotplug-cpu-migrate-a-task-within-its-cpuset.patch
hotplug-cpu-migrate-a-task-within-its-cpuset-fix.patch
hotplug-cpu-migrate-a-task-within-its-cpuset-whitespace-fix.patch
hotplug-cpu-migrate-a-task-within-its-cpuset-doc.patch
hook-up-group-scheduler-with-control-groups.patch
hook-up-group-scheduler-with-control-groups-fix.patch
uninline-forkc-exitc.patch
uninline-forkc-exitc-checkpatch-fixes.patch
detect-atomic-counter-underflows.patch
make-frame_pointer-default=y.patch
mutex-subsystem-synchro-test-module.patch
lockdep-show-held-locks-when-showing-a-stackdump.patch
kmap_atomic-debugging.patch
-
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