On Thu, 2010-10-14 at 00:07 +0530, Subrata Modak wrote:
> I get a bigger trace with this patch:
However i merged this test cases with LTP just now except the default
running part. I will raise a bug internally and try to see if a fix is
available.
Regards--
Subrata
>
> 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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