Messages in this thread |  | | Date | Sat, 21 Mar 2009 18:32:07 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 0/5] [GIT PULL] updates for tip/tracing/ftrace |
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On Sat, Mar 21, 2009 at 05:58:04PM +0100, Ingo Molnar wrote: > > * Ingo Molnar <mingo@elte.hu> wrote: > > > > > * Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > > > On Fri, 20 Mar 2009, Frederic Weisbecker wrote: > > > > > > > > > > > > VERBOSE_PRINTK_STRING("rcu_torture_reader task started"); > > > > > > - set_user_nice(current, 19); > > > > > > + set_user_nice(current, -1); > > > > > > if (irqreader && cur_ops->irqcapable) > > > > > > setup_timer_on_stack(&t, rcu_torture_timer, 0); > > > > > > > > > > i dont have a reproducer right now. Can you trigger it with latest > > > > > -tip, which has this commit included: > > > > > > > > > > 04cb9ac: rcu: rcu_barrier VS cpu_hotplug: Ensure callbacks in dead cpu are migrated to o > > > > > > > > > > ? > > > > > > > > > > Ingo > > > > > > > > > > > > I tested three times the same things but with 04cb9ac and... it didn't triggered > > > > anymore :-) > > > > > > So lets hope that was the culprit. > > > > > > Great work Frederic! > > > > No new lockups of this nature in overnight -tip testing. It's > > still a bit too early to tell for sure but it's promising ;-) > > just got a lockup again :-/ It hangs here: > > calling init_mmio_trace+0x0/0x12 @ 1 > initcall init_mmio_trace+0x0/0x12 returned 0 after 0 usecs > calling init_graph_trace+0x0/0x12 @ 1 > Testing tracer function_graph: > > and this time i got good stackdumps as well - see below. Config > attached. > > Ingo > > Testing tracer sched_switch: PASSED > initcall init_sched_switch_trace+0x0/0x12 returned 0 after 99609 usecs > calling init_stack_trace+0x0/0x12 @ 1 > Testing tracer sysprof: .. no entries found ..FAILED! > initcall init_stack_trace+0x0/0x12 returned -1 after 101562 usecs > initcall init_stack_trace+0x0/0x12 returned with error code -1 > calling init_function_trace+0x0/0x12 @ 1 > Testing tracer function: PASSED > initcall init_function_trace+0x0/0x12 returned 0 after 104492 usecs > calling init_irqsoff_tracer+0x0/0x2c @ 1 > Testing tracer irqsoff: .. no entries found ..FAILED! > Testing tracer preemptoff: .. no entries found ..FAILED! > Testing tracer preemptirqsoff: .. no entries found ..FAILED!
It's strange that the {*}_off tracers have failed.
> initcall init_irqsoff_tracer+0x0/0x2c returned 0 after 8789 usecs > calling init_wakeup_tracer+0x0/0x58 @ 1 > Testing tracer wakeup: .. no entries found ..FAILED!
This one too. (sysprof doesn't count, it fails for some weeks, I think it's not a hard deal to fix).
> initcall init_wakeup_tracer+0x0/0x58 returned -1 after 298828 usecs > initcall init_wakeup_tracer+0x0/0x58 returned with error code -1 > calling stack_trace_init+0x0/0xc7 @ 1 > initcall stack_trace_init+0x0/0xc7 returned 0 after 0 usecs > calling init_mmio_trace+0x0/0x12 @ 1 > initcall init_mmio_trace+0x0/0x12 returned 0 after 0 usecs > calling init_graph_trace+0x0/0x12 @ 1 > Testing tracer function_graph: <3>INFO: RCU detected CPU 0 stall (t=4294678940/10000 jiffies) > Pid: 1, comm: swapper Not tainted 2.6.29-rc8-tip-02752-g47b1aea-dirty #3264 > Call Trace: > <IRQ> [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff80211150>] print_context_stack+0xa0/0xd3 > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff8020fb26>] dump_trace+0x22d/0x2cc > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff80211008>] show_trace_log_lvl+0x51/0x5d > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff80211029>] show_trace+0x15/0x17 > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff802111fa>] dump_stack+0x77/0x81 > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff8029e6dd>] print_cpu_stall+0x40/0xa4 > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff8029e8be>] check_cpu_stall+0x49/0x76 > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff8029e902>] __rcu_pending+0x17/0xfc > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff8029ea13>] rcu_pending+0x2c/0x5e > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff8026abef>] update_process_times+0x3c/0x77 > [<ffffffff8020c79d>] return_to_handler+0x0/0x73 > [<ffffffff802875dd>] tick_periodic+0x6e/0x70
Still hanging in the timer interrupt. I guess it makes the timer interrupt servicing too slow and then once it is serviced, another one is raised.
But the cause is perhaps more complex
I think you have had too much hanging of this type. I'm preparing a fix that checks periodically if the function graph tracer is spending too much time in an interrupt.
I guess I could count the number of function executed between the irq entry and its exit.
That's the best: if we are hanging in an interrupt, it could be whatever interrupt and the jiffies could not be progressing so I can't rely on time but only on number of functions executed.
May be 10000 calls is a good threshold before killing the function graph inside an interrupt?
Let's try, I will also provide a way to dump the function graph traces from the ring-buffer on the screen, it could help to debug it in this case.
Thanks, Frederic.
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