On 7/20/2016 10:04 PM, Christoph Lameter wrote:
We are trying to test the patchset on x86 and are getting strange backtraces and aborts. It seems that the cpu before the cpu we are running on creates an irq_work event that causes a latency event on the next cpu. This is weird. Is there a new round robin IPI feature in the kernel that I am not aware of?
This seems to be from your clocksource declaring itself to be unstable, and then scheduling work to safely remove that timer. I haven't looked at this code before (in kernel/time/clocksource.c under CONFIG_CLOCKSOURCE_WATCHDOG) since the timers on arm64 and tile aren't unstable. Is it possible to boot your machine with a stable clocksource?
Backtraces from dmesg: [ 956.603223] latencytest/7928: task_isolation mode lost due to irq_work [ 956.610817] cpu 12: irq_work violating task isolation for latencytest/7928 on cpu 13 [ 956.619985] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 4.7.0-rc7-stream1 #1 [ 956.628765] Hardware name: Dell Inc. PowerEdge R630/0CNCJW, BIOS 2.0.2 03/15/2016 [ 956.637642] 0000000000000086 ce6735c7b39e7b81 ffff88103e783d00 ffffffff8134f6ff [ 956.646739] ffff88102c50d700 000000000000000d ffff88103e783d28 ffffffff811986f4 [ 956.655828] ffff88102c50d700 ffff88203cf97f80 000000000000000d ffff88103e783d68 [ 956.664924] Call Trace: [ 956.667945] <IRQ> [<ffffffff8134f6ff>] dump_stack+0x63/0x84 [ 956.674740] [<ffffffff811986f4>] task_isolation_debug_task+0xb4/0xd0 [ 956.682229] [<ffffffff810b4a13>] _task_isolation_debug+0x83/0xc0 [ 956.689331] [<ffffffff81179c0c>] irq_work_queue_on+0x9c/0x120 [ 956.696142] [<ffffffff811075e4>] tick_nohz_full_kick_cpu+0x44/0x50 [ 956.703438] [<ffffffff810b48d9>] wake_up_nohz_cpu+0x99/0x110 [ 956.710150] [<ffffffff810f57e1>] internal_add_timer+0x71/0xb0 [ 956.716959] [<ffffffff810f696b>] add_timer_on+0xbb/0x140 [ 956.723283] [<ffffffff81100ca0>] clocksource_watchdog+0x230/0x300 [ 956.730480] [<ffffffff81100a70>] ? __clocksource_unstable.isra.2+0x40/0x40 [ 956.738555] [<ffffffff810f5615>] call_timer_fn+0x35/0x120 [ 956.744973] [<ffffffff81100a70>] ? __clocksource_unstable.isra.2+0x40/0x40 [ 956.753046] [<ffffffff810f64cc>] run_timer_softirq+0x23c/0x2f0 [ 956.759952] [<ffffffff816d4397>] __do_softirq+0xd7/0x2c5 [ 956.766272] [<ffffffff81091245>] irq_exit+0xf5/0x100 [ 956.772209] [<ffffffff816d41d2>] smp_apic_timer_interrupt+0x42/0x50 [ 956.779600] [<ffffffff816d231c>] apic_timer_interrupt+0x8c/0xa0 [ 956.786602] <EOI> [<ffffffff81569eb0>] ? poll_idle+0x40/0x80 [ 956.793490] [<ffffffff815697dc>] cpuidle_enter_state+0x9c/0x260 [ 956.800498] [<ffffffff815699d7>] cpuidle_enter+0x17/0x20 [ 956.806810] [<ffffffff810cf497>] cpu_startup_entry+0x2b7/0x3a0 [ 956.813717] [<ffffffff81050e6c>] start_secondary+0x15c/0x1a0 [ 1036.601758] cpu 12: irq_work violating task isolation for latencytest/8447 on cpu 13 [ 1036.610922] CPU: 12 PID: 0 Comm: swapper/12 Not tainted 4.7.0-rc7-stream1 #1 [ 1036.619692] Hardware name: Dell Inc. PowerEdge R630/0CNCJW, BIOS 2.0.2 03/15/2016 [ 1036.628551] 0000000000000086 ce6735c7b39e7b81 ffff88103e783d00 ffffffff8134f6ff [ 1036.637648] ffff88102dca0000 000000000000000d ffff88103e783d28 ffffffff811986f4 [ 1036.646741] ffff88102dca0000 ffff88203cf97f80 000000000000000d ffff88103e783d68 [ 1036.655833] Call Trace: [ 1036.658852] <IRQ> [<ffffffff8134f6ff>] dump_stack+0x63/0x84 [ 1036.665649] [<ffffffff811986f4>] task_isolation_debug_task+0xb4/0xd0 [ 1036.673136] [<ffffffff810b4a13>] _task_isolation_debug+0x83/0xc0 [ 1036.680237] [<ffffffff81179c0c>] irq_work_queue_on+0x9c/0x120 [ 1036.687091] [<ffffffff811075e4>] tick_nohz_full_kick_cpu+0x44/0x50 [ 1036.694388] [<ffffffff810b48d9>] wake_up_nohz_cpu+0x99/0x110 [ 1036.701089] [<ffffffff810f57e1>] internal_add_timer+0x71/0xb0 [ 1036.707896] [<ffffffff810f696b>] add_timer_on+0xbb/0x140 [ 1036.714210] [<ffffffff81100ca0>] clocksource_watchdog+0x230/0x300 [ 1036.721411] [<ffffffff81100a70>] ? __clocksource_unstable.isra.2+0x40/0x40 [ 1036.729478] [<ffffffff810f5615>] call_timer_fn+0x35/0x120 [ 1036.735899] [<ffffffff81100a70>] ? __clocksource_unstable.isra.2+0x40/0x40 [ 1036.743970] [<ffffffff810f64cc>] run_timer_softirq+0x23c/0x2f0 [ 1036.750878] [<ffffffff816d4397>] __do_softirq+0xd7/0x2c5 [ 1036.757199] [<ffffffff81091245>] irq_exit+0xf5/0x100 [ 1036.763132] [<ffffffff816d41d2>] smp_apic_timer_interrupt+0x42/0x50 [ 1036.770520] [<ffffffff816d231c>] apic_timer_interrupt+0x8c/0xa0 [ 1036.777520] <EOI> [<ffffffff81569eb0>] ? poll_idle+0x40/0x80 [ 1036.784410] [<ffffffff815697dc>] cpuidle_enter_state+0x9c/0x260 [ 1036.791413] [<ffffffff815699d7>] cpuidle_enter+0x17/0x20 [ 1036.797734] [<ffffffff810cf497>] cpu_startup_entry+0x2b7/0x3a0 [ 1036.804641] [<ffffffff81050e6c>] start_secondary+0x15c/0x1a0
-- Chris Metcalf, Mellanox Technologies http://www.mellanox.com -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
