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Date: Sun, 11 Jan 2015 11:59:45 +0000 From: "Stoidner, Christoph" <c.stoidner@...ero.de> To: "paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: AW: Question concerning RCU Hi Paul, many thanks for your fast answer! Now I have changed my application in that way, that it does not require Xenomai/I-Pipe anymore. That means my kernel is build now from mainline source, with preempt_rt only and no Xenomai or I-Pipe. However the problem is exact the same. After some runtime (minutes or hours) the kernel freezes and JTAG debugging shows that it ends-up in an endless loop in rcu_print_task_stall (as described before). > First I have seen this. Were you doing lots of CPU-hotplug operations? My system has only one core. So I think there should not be any CPU-hotplugging. > If you have more CPUs than the value of CONFIG_RCU_FANOUT (which > defaults to 16), and if your workload offlined a full block of CPUs (full > blocks being CPUs 0-15, 16-31, 32-47, and so on for the default value > of CONFIG_RCU_FANOUT), then there is a theoretical issue that -might- > cause the problem that you are seeing. Also this could not only happen on a single core system. Am I right? I have no idea how to find the problem. Do you have any more hints or ideas? Here is a backtrace when the problem has occurred on the system without Xenomai/I-Pipe: #0 rcu_print_task_stall (rnp=0xc0498dc8 <rcu_preempt_state>) at kernel/rcutree_plugin.h:528 #1 0xc005cabc in print_other_cpu_stall (rsp=0xc0498dc8 <rcu_preempt_state>) at kernel/rcutree.c:885 #2 check_cpu_stall (rdp=0x80000093, rsp=0xc0498dc8 <rcu_preempt_state>) at kernel/rcutree.c:977 #3 __rcu_pending (rdp=0x80000093, rsp=0xc0498dc8 <rcu_preempt_state>) at kernel/rcutree.c:2750 #4 rcu_pending (cpu=<optimized out>) at kernel/rcutree.c:2800 #5 rcu_check_callbacks (cpu=<optimized out>, user=<optimized out>) at kernel/rcutree.c:2179 #6 0xc0027648 in update_process_times (user_tick=0) at kernel/timer.c:1427 #7 0xc004e840 in tick_sched_timer (timer=0xc0498860 <tick_cpu_sched>) at kernel/time/tick-sched.c:1095 #8 0xc003a0dc in __run_hrtimer (timer=0xc0498860 <tick_cpu_sched>, now=<optimized out>) at kernel/hrtimer.c:1363 #9 0xc003ab4c in hrtimer_interrupt (dev=<optimized out>) at kernel/hrtimer.c:1582 #10 0xc02bf7bc in mxs_timer_interrupt (irq=<optimized out>, dev_id=<optimized out>) at drivers/clocksource/mxs_timer.c:132 #11 0xc0055154 in handle_irq_event_percpu (desc=0xc7804c00, action=0xc04b0520 <mxs_timer_irq>) at kernel/irq/handle.c:144 #12 0xc0055320 in handle_irq_event (desc=0xc7804c00) at kernel/irq/handle.c:197 #13 0xc00578b8 in handle_level_irq (irq=<optimized out>, desc=0xc7804c00) at kernel/irq/chip.c:406 #14 0xc0054aec in generic_handle_irq_desc (desc=<optimized out>, irq=16) at include/linux/irqdesc.h:115 #15 generic_handle_irq (irq=16) at kernel/irq/irqdesc.c:314 #16 0xc000f58c in handle_IRQ (irq=16, regs=<optimized out>) at arch/arm/kernel/irq.c:80 #17 0xc000e360 in __irq_svc () at arch/arm/kernel/entry-armv.S:202 #18 0xc000e360 in __irq_svc () at arch/arm/kernel/entry-armv.S:202 #19 0xc000e360 in __irq_svc () at arch/arm/kernel/entry-armv.S:202 #20 0xc000e360 in __irq_svc () at arch/arm/kernel/entry-armv.S:202 ... Thanks and regards, Christoph -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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