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Date: Thu, 25 Sep 2014 16:35:49 +0200 (CEST) From: Thomas Gleixner <tglx@...utronix.de> To: Dave Jones <davej@...hat.com> cc: linux-mm@...ck.org, Frederic Weisbecker <fweisbec@...il.com>, Peter Zijlstra <peterz@...radead.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: hrtimer deadlock caused by nohz_full On Thu, 25 Sep 2014, Dave Jones wrote: > Got this on a box that had been fuzzing for 12 hours or so. > There's also some timer stuff going on htere, so cc'ing the usual suspects. And it's a hrtimer lockup > [<ffffffffa10f95f8>] ? hrtimer_try_to_cancel+0x58/0x1f0 > [<ffffffffa10d103d>] ? lock_release+0x1d/0x300 > [<ffffffffa10d103d>] ? lock_release+0x1d/0x300 > [<ffffffffa10f95f8>] ? hrtimer_try_to_cancel+0x58/0x1f0 > [<ffffffffa10d103d>] ? lock_release+0x1d/0x300 > <<EOE>> <IRQ> [<ffffffffa1823ac4>] _raw_spin_unlock_irqrestore+0x24/0x70 > [<ffffffffa10f95f8>] hrtimer_try_to_cancel+0x58/0x1f0 > [<ffffffffa10f97aa>] hrtimer_cancel+0x1a/0x30 > [<ffffffffa110a0e7>] tick_nohz_restart+0x17/0x90 > [<ffffffffa110af38>] __tick_nohz_full_check+0xc8/0xe0 > [<ffffffffa110af5e>] nohz_full_kick_work_func+0xe/0x10 > [<ffffffffa117c9bf>] irq_work_run_list+0x4f/0x70 > [<ffffffffa117ca0a>] irq_work_run+0x2a/0x60 > [<ffffffffa10f82eb>] update_process_times+0x5b/0x70 > [<ffffffffa1109dc5>] tick_sched_handle.isra.21+0x25/0x60 > [<ffffffffa110a0b1>] tick_sched_timer+0x41/0x60 > [<ffffffffa10f8c71>] __run_hrtimer+0x81/0x480 > [<ffffffffa110a070>] ? tick_sched_do_timer+0x90/0x90 > [<ffffffffa10f9b27>] hrtimer_interrupt+0x107/0x260 > [<ffffffffa10331a4>] local_apic_timer_interrupt+0x34/0x60 > [<ffffffffa182734f>] smp_apic_timer_interrupt+0x3f/0x60 > [<ffffffffa182576f>] apic_timer_interrupt+0x6f/0x80 hrtimer_interrupt tick_sched_timer tick_sched_handle update_process_times irq_work_run irq_work_run_list nohz_full_kick_work_func __tick_nohz_full_check tick_nohz_restart hrtimer_cancel And that hrtimer_cancel is: static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) { hrtimer_cancel(&ts->sched_timer); Now, that's really bad because we are in the timer callback of ts->sched_timer. So hrtimer_cancel will loop forever waiting for the callback to complete. Frederic !?!? Thanks, tglx -- 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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