2.6.23-stable review patch. If anyone has any objections, please let us know. ------------------ From: Ingo Molnar This is a merge of commits a5f2ce3c6024a5bb895647b6bd88ecae5001020a and 43581a10075492445f65234384210492ff333eba in mainline to fix a warning in the 2.6.23.3 kernel release. softlockup watchdog: style cleanups kernel/softirq.c grew a few style uncleanlinesses in the past few months, clean that up. No functional changes: text data bss dec hex filename 1126 76 4 1206 4b6 softlockup.o.before 1129 76 4 1209 4b9 softlockup.o.after ( the 3 bytes .text increase is due to the "<1>" appended to one of the printk messages. ) Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds 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! [] show_trace_log_lvl+0x19/0x2e [] show_trace+0x12/0x14 [] dump_stack+0x14/0x16 [] softlockup_tick+0xbe/0xd0 [] run_local_timers+0x12/0x14 [] update_process_times+0x3e/0x63 [] tick_sched_timer+0x7c/0xc0 [] hrtimer_interrupt+0x135/0x1ba [] smp_apic_timer_interrupt+0x6e/0x80 [] apic_timer_interrupt+0x33/0x38 [] syscall_call+0x7/0xb ======================= The new format is: BUG: soft lockup detected on CPU#1! [prctl:2363] Pid: 2363, comm: prctl EIP: 0060:[] 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 [] show_trace_log_lvl+0x19/0x2e [] show_trace+0x12/0x14 [] show_regs+0x1ab/0x1b3 [] softlockup_tick+0xef/0x108 [] run_local_timers+0x12/0x14 [] update_process_times+0x3e/0x63 [] tick_sched_timer+0x7c/0xc0 [] hrtimer_interrupt+0x135/0x1ba [] smp_apic_timer_interrupt+0x6e/0x80 [] apic_timer_interrupt+0x33/0x38 [] 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 Signed-off-by: Satyam Sharma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/softlockup.c | 37 +++++++++++++++++++++++-------------- 1 file changed, 23 insertions(+), 14 deletions(-) --- a/kernel/softlockup.c +++ b/kernel/softlockup.c @@ -15,13 +15,16 @@ #include #include +#include + static DEFINE_SPINLOCK(print_lock); static DEFINE_PER_CPU(unsigned long, touch_timestamp); static DEFINE_PER_CPU(unsigned long, print_timestamp); static DEFINE_PER_CPU(struct task_struct *, watchdog_task); -static int did_panic = 0; +static int did_panic; +int softlockup_thresh = 10; static int softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) @@ -70,6 +73,7 @@ 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) { @@ -99,21 +103,26 @@ 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 + softlockup_thresh)) + return; + + 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); + spin_lock(&print_lock); + printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", + this_cpu, now - touch_timestamp, + current->comm, current->pid); + if (regs) + show_regs(regs); + else dump_stack(); - spin_unlock(&print_lock); - } + spin_unlock(&print_lock); } /* * The watchdog thread - runs every second and touches the timestamp. */ -static int watchdog(void * __bind_cpu) +static int watchdog(void *__bind_cpu) { struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; @@ -151,13 +160,13 @@ cpu_callback(struct notifier_block *nfb, BUG_ON(per_cpu(watchdog_task, hotcpu)); p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); if (IS_ERR(p)) { - printk("watchdog for %i failed\n", hotcpu); + printk(KERN_ERR "watchdog for %i failed\n", hotcpu); return NOTIFY_BAD; } - per_cpu(touch_timestamp, hotcpu) = 0; - per_cpu(watchdog_task, hotcpu) = p; + per_cpu(touch_timestamp, hotcpu) = 0; + per_cpu(watchdog_task, hotcpu) = p; kthread_bind(p, hotcpu); - break; + break; case CPU_ONLINE: case CPU_ONLINE_FROZEN: wake_up_process(per_cpu(watchdog_task, hotcpu)); @@ -177,7 +186,7 @@ cpu_callback(struct notifier_block *nfb, kthread_stop(p); break; #endif /* CONFIG_HOTPLUG_CPU */ - } + } return NOTIFY_OK; } -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/