Re: [LTP] [PATCH v2] Add ftrace-stress-test to LTP

[Subrata Modak <subrata@linux.vnet.ibm.com>]

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.zijlstra@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.carstens@de.ibm.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> LKML-Reference: <1285165776.2275.1022.camel@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, &param);
> +
> +		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, &param);
>  		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 */
> +};
> 
> 
> 


------------------------------------------------------------------------------
Beautiful is writing same markup. Internet Explorer 9 supports
standards for HTML5, CSS3, SVG 1.1,  ECMAScript5, and DOM L2 & L3.
Spend less time writing and  rewriting code and more time creating great
experiences on the web. Be a part of the beta today.
http://p.sf.net/sfu/beautyoftheweb
_______________________________________________
Ltp-list mailing list
Ltp-list@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/ltp-list