I get a bigger trace with this patch:
Unable to handle kernel paging request for data at address 0x00000000
Faulting instruction address: 0xc0000000002133f0
cpu 0x2: Vector: 300 (Data Access) at [c0000000d9f8b560]
pc: c0000000002133f0: .trace_clock_global+0xb4/0x2a0
lr: c000000000213458: .trace_clock_global+0x11c/0x2a0
sp: c0000000d9f8b7e0
msr: 800000000200b032
dar: 0
dsisr: 40000000
current = 0xc0000000d9f7d100
paca = 0xc000000007fc8e00
pid = 1667, comm = ftrace_stack_tr
Unrecoverable FP Unavailable Exception 800 at c0000000016a9540
cpu 0x0: Vector: 8Unable to handle0 kernel paging r0 equest for data (at
address 0xbffFffffe0175b688
PU UnavaFaulting instruciltion address: 0xac0000000001017fcb
le) at [c0000000d9f8a6a0]
p pc: c0000000016a9540: etnetre r? ?f ofro rh ehlepl
lr: [c000000000016a9540: key_type_dns_resolver+0x15110/0x365f8
sp: c0000000018804e8
msr: 8000000000001032
current = 0xc0000000d838d100
paca = 0xc000000007fc8000
pid = 1668, comm = ftrace_stack_ma
pid = 1668, cc0000000002226b0 .rb_reserve_next_event+0x20c/0x804
[c0000000d9f8b9b0] c000000000223178 .ring_buffer_lock_reserve
+0x24c/0x2a4
[c0000000d9f8ba40] c00000000022d6f4 .trace_buffer_lock_reserve+0x58/0xe4
[c0000000d9f8baf0] c00000000022ec9c .trace_current_buffer_lock_reserve
+0x44/0x6c
[c0000000d9f8bb80] c000000000011c5c .ftrace_raw_event_hcall_entry
+0x7c/0x144
[c0000000d9f8bc40] c000000000096624 .__trace_hcall_entry+0xa0/0xec
[c0000000d9f8bcd0] c00000000009786c .plpar_hcall_norets+0x50/0xd0
[c0000000d9f8bd40] c0000000000749c8 .__spin_yield+0x130/0x15c
[c0000000d9f8bdd0] c000000000213458 .trace_clock_global+0x11c/0x2a0
[c0000000d9f8be90] c0000000002226b0 .rb_reserve_next_event+0x20c/0x804
[c0000000d9f8bfa0] c000000000223178 .ring_buffer_lock_reserve
+0x24c/0x2a4
[c0000000d9f8c030] c00000000022d6f4 .trace_buffer_lock_reserve+0x58/0xe4
[c0000000d9f8c0e0] c00000000022ec9c .trace_current_buffer_lock_reserve
+0x44/0x6c
[c0000000d9f8c170] c000000000011c5c .ftrace_raw_event_hcall_entry
+0x7c/0x144
[c0000000d9f8c230] c000000000096624 .__trace_hcall_entry+0xa0/0xec
[c0000000d9f8c2c0] c00000000009786c .plpar_hcall_norets+0x50/0xd0
[c0000000d9f8c330] c0000000000749c8 .__spin_yield+0x130/0x15c
[c0000000d9f8c3c0] c000000000213458 .trace_clock_global+0x11c/0x2a0
[c0000000d9f8c480] c0000000002226b0 .rb_reserve_next_event+0x20c/0x804
[c0000000d9f8c590] c000000000223178 .ring_buffer_lock_reserve
+0x24c/0x2a4
[c0000000d9f8c620] c00000000022d6f4 .trace_buffer_lock_reserve+0x58/0xe4
[c0000000d9f8c6d0] c00000000022ec9c .trace_current_buffer_lock_reserve
+0x44/0x6c
[c0000000d9f8c760] c000000000011c5c .ftrace_raw_event_hcall_entry
+0x7c/0x144
[c0000000d9f8c820] c000000000096624 .__trace_hcall_entry+0xa0/0xec
[c0000000d9f8c8b0] c00000000009786c .plpar_hcall_norets+0x50/0xd0
[c0000000d9f8c920] c0000000000749c8 .__spin_yield+0x130/0x15c
[c0000000d9f8c9b0] c000000000213458 .trace_clock_global+0x11c/0x2a0
[c0000000d9f8ca70] c0000000002226b0 .rb_reserve_next_event+0x20c/0x804
[c0000000d9f8cb80] c000000000223178 .ring_buffer_lock_reserve
+0x24c/0x2a4
[c0000000d9f8cc10] c00000000022d6f4 .trace_buffer_lock_reserve+0x58/0xe4
[c0000000d9f8ccc0] c00000000022ec9c .trace_current_buffer_lock_reserve
+0x44/0x6c
[c0000000d9f8cd50] c000000000011c5c .ftrace_raw_event_hcall_entry
+0x7c/0x144
[c0000000d9f8ce10] c000000000096624 .__trace_hcall_entry+0xa0/0xec
[c0000000d9f8cea0] c00000000009786c .plpar_hcall_norets+0x50/0xd0
[c0000000d9f8cf10] c0000000000749c8 .__spin_yield+0x130/0x15c
[c0000000d9f8cfa0] c000000000213458 .trace_clock_global+0x11c/0x2a0
[c0000000d9f8d060] c0000000002226b0 .rb_reserve_next_event+0x20c/0x804
[c0000000d9f8d170] c000000000223178 .ring_buffer_lock_reserve
+0x24c/0x2a4
[c0000000d9f8d200] c00000000022d6f4 .trace_buffer_lock_reserve+0x58/0xe4
[c0000000d9f8d2b0] c00000000022ec9c .trace_current_buffer_lock_reserve
+0x44/0x6c
[c0000000d9f8d340] c000000000011c5c .ftrace_raw_event_hcall_entry
+0x7c/0x144
[c0000000d9f8d400] c000000000096624 .__trace_hcall_entry+0xa0/0xec
[c0000000d9f8d490] c00000000009786c .plpar_hcall_norets+0x50/0xd0
[c0000000d9f8d500] c0000000000749c8 .__spin_yield+0x130/0x15c
[c0000000d9f8d590] c000000000213458 .trace_clock_global+0x11c/0x2a0
[c0000000d9f8d650] c0000000002226b0 .rb_reserve_next_event+0x20c/0x804
[c0000000d9f8d760] c000000000223178 .ring_buffer_lock_reserve
+0x24c/0x2a4
[c0000000d9f8d7f0] c00000000022d6f4 .trace_buffer_lock_reserve+0x58/0xe4
[c0000000d9f8d8a0] c00000000022ec9c .trace_current_buffer_lock_reserve
+0x44/0x6c
[c0000000d9f8d930] c000000000011c5c .ftrace_raw_event_hcall_entry
+0x7c/0x144
[c0000000d9f8d9f0] c000000000096624 .__trace_hcall_entry+0xa0/0xec
[c0000000d9f8da80] c00000000009786c .plpar_hcall_norets+0x50/0xd0
[c0000000d9f8daf0] c0000000000749c8 .__spin_yield+0x130/0x15c
[c0000000d9f8db80] c000000000213458 .trace_clock_global+0x11c/0x2a0
[c0000000d9f8dc40] c0000000002226b0 .rb_reserve_next_event+0x20c/0x804
[c0000000d9f8dd50] c000000000223178 .ring_buffer_lock_reserve
+0x24c/0x2a4
[c0000000d9f8dde0] c00000000022d6f4 .trace_buffer_lock_reserve+0x58/0xe4
[c0000000d9f8de90] c00000000022ec9c .trace_current_buffer_lock_reserve
+0x44/0x6c
[c0000000d9f8df20] c000000000011c5c .ftrace_raw_event_hcall_entry
+0x7c/0x144
[c0000000d9f8dfe0] c000000000096624 .__trace_hcall_entry+0xa0/0xec
[c0000000d9f8e070] c00000000009786c .plpar_hcall_norets+0x50/0xd0
[c0000000d9f8e0e0] c0000000000749c8 .__spin_yield+0x130/0x15c
[c0000000d9f8e170] c000000000213458 .trace_clock_global+0x11c/0x2a0
[c0000000d9f8e230] c0000000002226b0 .rb_reserve_next_event+0x20c/0x804
Regards--
Subrata
On Wed, 2010-10-13 at 19:29 +0800, Li Zefan wrote:
> Li Zefan wrote:
> > Li Zefan wrote:
> >> Subrata Modak wrote:
> >>> Li,
> >>>
> >>> Can you kindly fix the below issues and send me a new patch ?
> >>>
> >> Sure, I will.
> >>
> >
> > At a first glance, the kernel bug doesn't seem to come from ftrace,
> > at least not directly from it.
> >
> > Question:
> >
> > Can you trigger this bug in latest kernel (2.6.36-rc7)? If you
> > haven't tried it, could you test it? Thanks!
> >
>
> I got a patch from Peter, though he's not sure about the bug yet.
> So could you try this?
>
> Note, I don't know if this patch can be applied to 2.6.35-4..
>
> ======================
>
> (From Peter)
>
> Hrmm, not something I've seen before.. but since the migration thread
> and stop_machine are involved, does the below patch which rewrites the
> migration-thread/stop_macehine/scheduler interaction cure this?
>
> This patch is probably .37 fodder, but who knows..
>
> ---
> Subject: sched: Create special class for stop/migrate work
> From: Peter Zijlstra <a.p.zijls...@chello.nl>
> Date: Wed Sep 22 13:53:15 CEST 2010
>
> In order to separate the stop/migrate work thread from the SCHED_FIFO
> implementation, create a special class for it that is of higher priority
> than SCHED_FIFO itself.
>
> This currently solves a problem where cpu-hotplug consumes so much cpu-time
> that the SCHED_FIFO class gets throttled, but has the bandwidth replenishment
> timer pending on the now dead cpu.
>
> It is also required for when we add the planned deadline scheduling class
> above SCHED_FIFO, as the stop/migrate thread still needs to transcent those
> tasks.
>
> Tested-by: Heiko Carstens <heiko.carst...@de.ibm.com>
> Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl>
> LKML-Reference: <1285165776.2275.1022.ca...@laptop>
> ---
> kernel/sched.c | 54 ++++++++++++++++++++----
> kernel/sched_stoptask.c | 108
> ++++++++++++++++++++++++++++++++++++++++++++++++
> kernel/stop_machine.c | 8 ++-
> 3 files changed, 158 insertions(+), 12 deletions(-)
>
> Index: linux-2.6/kernel/sched.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched.c
> +++ linux-2.6/kernel/sched.c
> @@ -486,7 +486,7 @@ struct rq {
> */
> unsigned long nr_uninterruptible;
>
> - struct task_struct *curr, *idle;
> + struct task_struct *curr, *idle, *stop;
> unsigned long next_balance;
> struct mm_struct *prev_mm;
>
> @@ -1837,7 +1837,7 @@ static inline void __set_task_cpu(struct
>
> static const struct sched_class rt_sched_class;
>
> -#define sched_class_highest (&rt_sched_class)
> +#define sched_class_highest (&stop_sched_class)
> #define for_each_class(class) \
> for (class = sched_class_highest; class; class = class->next)
>
> @@ -1917,10 +1917,41 @@ static void deactivate_task(struct rq *r
> #include "sched_idletask.c"
> #include "sched_fair.c"
> #include "sched_rt.c"
> +#include "sched_stoptask.c"
> #ifdef CONFIG_SCHED_DEBUG
> # include "sched_debug.c"
> #endif
>
> +void sched_set_stop_task(int cpu, struct task_struct *stop)
> +{
> + struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
> + struct task_struct *old_stop = cpu_rq(cpu)->stop;
> +
> + if (stop) {
> + /*
> + * Make it appear like a SCHED_FIFO task, its something
> + * userspace knows about and won't get confused about.
> + *
> + * Also, it will make PI more or less work without too
> + * much confusion -- but then, stop work should not
> + * rely on PI working anyway.
> + */
> + sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
> +
> + stop->sched_class = &stop_sched_class;
> + }
> +
> + cpu_rq(cpu)->stop = stop;
> +
> + if (old_stop) {
> + /*
> + * Reset it back to a normal scheduling class so that
> + * it can die in pieces.
> + */
> + old_stop->sched_class = &rt_sched_class;
> + }
> +}
> +
> /*
> * __normal_prio - return the priority that is based on the static prio
> */
> @@ -3720,17 +3751,13 @@ pick_next_task(struct rq *rq)
> return p;
> }
>
> - class = sched_class_highest;
> - for ( ; ; ) {
> + for_each_class(class) {
> p = class->pick_next_task(rq);
> if (p)
> return p;
> - /*
> - * Will never be NULL as the idle class always
> - * returns a non-NULL p:
> - */
> - class = class->next;
> }
> +
> + BUG(); /* the idle class will always have a runnable task */
> }
>
> /*
> @@ -4659,6 +4686,15 @@ static int __sched_setscheduler(struct t
> */
> rq = __task_rq_lock(p);
>
> + /*
> + * Changing the policy of the stop threads its a very bad idea
> + */
> + if (p == rq->stop) {
> + __task_rq_unlock(rq);
> + raw_spin_unlock_irqrestore(&p->pi_lock, flags);
> + return -EINVAL;
> + }
> +
> #ifdef CONFIG_RT_GROUP_SCHED
> if (user) {
> /*
> Index: linux-2.6/kernel/stop_machine.c
> ===================================================================
> --- linux-2.6.orig/kernel/stop_machine.c
> +++ linux-2.6/kernel/stop_machine.c
> @@ -287,11 +287,12 @@ static int cpu_stopper_thread(void *data
> goto repeat;
> }
>
> +extern void sched_set_stop_task(int cpu, struct task_struct *stop);
> +
> /* manage stopper for a cpu, mostly lifted from sched migration thread mgmt
> */
> static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb,
> unsigned long action, void *hcpu)
> {
> - struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
> unsigned int cpu = (unsigned long)hcpu;
> struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
> struct task_struct *p;
> @@ -304,13 +305,13 @@ static int __cpuinit cpu_stop_cpu_callba
> cpu);
> if (IS_ERR(p))
> return NOTIFY_BAD;
> - sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m);
> get_task_struct(p);
> + kthread_bind(p, cpu);
> + sched_set_stop_task(cpu, p);
> stopper->thread = p;
> break;
>
> case CPU_ONLINE:
> - kthread_bind(stopper->thread, cpu);
> /* strictly unnecessary, as first user will wake it */
> wake_up_process(stopper->thread);
> /* mark enabled */
> @@ -325,6 +326,7 @@ static int __cpuinit cpu_stop_cpu_callba
> {
> struct cpu_stop_work *work;
>
> + sched_set_stop_task(cpu, NULL);
> /* kill the stopper */
> kthread_stop(stopper->thread);
> /* drain remaining works */
> Index: linux-2.6/kernel/sched_stoptask.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6/kernel/sched_stoptask.c
> @@ -0,0 +1,108 @@
> +/*
> + * stop-task scheduling class.
> + *
> + * The stop task is the highest priority task in the system, it preempts
> + * everything and will be preempted by nothing.
> + *
> + * See kernel/stop_machine.c
> + */
> +
> +#ifdef CONFIG_SMP
> +static int
> +select_task_rq_stop(struct rq *rq, struct task_struct *p,
> + int sd_flag, int flags)
> +{
> + return task_cpu(p); /* stop tasks as never migrate */
> +}
> +#endif /* CONFIG_SMP */
> +
> +static void
> +check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
> +{
> + resched_task(rq->curr); /* we preempt everything */
> +}
> +
> +static struct task_struct *pick_next_task_stop(struct rq *rq)
> +{
> + struct task_struct *stop = rq->stop;
> +
> + if (stop && stop->state == TASK_RUNNING)
> + return stop;
> +
> + return NULL;
> +}
> +
> +static void
> +enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
> +{
> +}
> +
> +static void
> +dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
> +{
> +}
> +
> +static void yield_task_stop(struct rq *rq)
> +{
> + BUG(); /* the stop task should never yield, its pointless. */
> +}
> +
> +static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
> +{
> +}
> +
> +static void task_tick_stop(struct rq *rq, struct task_struct *curr, int
> queued)
> +{
> +}
> +
> +static void set_curr_task_stop(struct rq *rq)
> +{
> +}
> +
> +static void switched_to_stop(struct rq *rq, struct task_struct *p,
> + int running)
> +{
> + BUG(); /* its impossible to change to this class */
> +}
> +
> +static void prio_changed_stop(struct rq *rq, struct task_struct *p,
> + int oldprio, int running)
> +{
> + BUG(); /* how!?, what priority? */
> +}
> +
> +static unsigned int
> +get_rr_interval_stop(struct rq *rq, struct task_struct *task)
> +{
> + return 0;
> +}
> +
> +/*
> + * Simple, special scheduling class for the per-CPU stop tasks:
> + */
> +static const struct sched_class stop_sched_class = {
> + .next = &rt_sched_class,
> +
> + .enqueue_task = enqueue_task_stop,
> + .dequeue_task = dequeue_task_stop,
> + .yield_task = yield_task_stop,
> +
> + .check_preempt_curr = check_preempt_curr_stop,
> +
> + .pick_next_task = pick_next_task_stop,
> + .put_prev_task = put_prev_task_stop,
> +
> +#ifdef CONFIG_SMP
> + .select_task_rq = select_task_rq_stop,
> +#endif
> +
> + .set_curr_task = set_curr_task_stop,
> + .task_tick = task_tick_stop,
> +
> + .get_rr_interval = get_rr_interval_stop,
> +
> + .prio_changed = prio_changed_stop,
> + .switched_to = switched_to_stop,
> +
> + /* no .task_new for stop tasks */
> +};
>
>
>
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