Re: [tip:sched/urgent] sched: Check sched_domain before computing group power

[Yinghai Lu <yinghai@kernel.org>]

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On Wed, Nov 27, 2013 at 11:07 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> On Wed, Nov 27, 2013 at 7:02 PM, David Rientjes <rientjes@google.com> wrote:

> maybe not related, now in another system, linus's tree + Srikar's patch.
>
> got
>
> [   33.546361] divide error: 0000 [#1]
> SMP
> [   33.589436] Modules linked in:
> [   33.592869] CPU: 15 PID: 567 Comm: kworker/u482:0 Not tainted
> 3.13.0-rc1-yh-00324-gcf1be1c-dirty #10
> [   33.603075] Hardware name: Oracle Corporation
> [   33.609571] calling  ipc_ns_init+0x0/0x14 @ 1
> [   33.609575] initcall ipc_ns_init+0x0/0x14 returned 0 after 0 usecs
> [   33.609577] calling  init_mmap_min_addr+0x0/0x16 @ 1
> [   33.609579] initcall init_mmap_min_addr+0x0/0x16 returned 0 after 0 usecs
> [   33.609583] calling  init_cpufreq_transition_notifier_list+0x0/0x1b @ 1
> [   33.609621] initcall init_cpufreq_transition_notifier_list+0x0/0x1b
> returned 0 after 0 usecs
> [   33.609624] calling  net_ns_init+0x0/0xfa @ 1
> [   33.677194] task: ffff897c5ba5c8c0 ti: ffff897c5ba8e000 task.ti:
> ffff897c5ba8e000
> [   33.685558] RIP: 0010:[<ffffffff810dbf2c>]  [<ffffffff810dbf2c>]
> find_busiest_group+0x2ac/0x880
> [   33.695310] RSP: 0000:ffff897c5ba8f9a8  EFLAGS: 00010046
> [   33.701253] RAX: 000000000001dfff RBX: 00000000ffffffff RCX: 000000000001e000
> [   33.709226] RDX: 0000000000000000 RSI: 0000000000000078 RDI: 0000000000000000
> [   33.717198] RBP: ffff897c5ba8fb08 R08: 0000000000000000 R09: 0000000000000000
> [   33.725178] R10: 0000000000000000 R11: 000000000001e000 R12: ffff897c5ba8fa90
> [   33.733156] R13: ffff897c5ad61d80 R14: 0000000000000000 R15: ffff897c5ba8fba0
> [   33.741132] FS:  0000000000000000(0000) GS:ffff897d7c200000(0000)
> knlGS:0000000000000000
> [   33.750164] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   33.756593] CR2: 0000000000000168 CR3: 0000000002a14000 CR4: 00000000001407e0
> [   33.764571] Stack:
> [   33.766822]  0000000000000000 0000000000000046 0000000000000048
> 0000000000000000
> [   33.775141]  ffff897c5ad61d98 ffff897c5ba8fa20 0000000000000036
> 00000000000003ab
> [   33.783461]  00000000000003ab 0000000000000139 00000000000044e8
> 0000000100000003
> [   33.791789] Call Trace:
> [   33.794549]  [<ffffffff810dc6c8>] load_balance+0x1c8/0x8d0
> [   33.800701]  [<ffffffff810ee65b>] ? __lock_acquire+0xadb/0xce0
> [   33.807222]  [<ffffffff810dd2d1>] idle_balance+0x101/0x1c0
> [   33.813355]  [<ffffffff810dd214>] ? idle_balance+0x44/0x1c0
> [   33.819618]  [<ffffffff8207a5bb>] __schedule+0x2cb/0xa10
> [   33.825584]  [<ffffffff810e86c8>] ? trace_hardirqs_off_caller+0x28/0x160
> [   33.833089]  [<ffffffff810e880d>] ? trace_hardirqs_off+0xd/0x10
> [   33.839731]  [<ffffffff810d3b84>] ? local_clock+0x34/0x60
> [   33.845788]  [<ffffffff810ba7bb>] ? worker_thread+0x2db/0x370
> [   33.852241]  [<ffffffff8207f8a0>] ? _raw_spin_unlock_irq+0x30/0x40
> [   33.859150]  [<ffffffff8207ad65>] schedule+0x65/0x70
> [   33.864700]  [<ffffffff810ba7c0>] worker_thread+0x2e0/0x370
> [   33.870932]  [<ffffffff810ec17d>] ? trace_hardirqs_on+0xd/0x10
> [   33.877472]  [<ffffffff810ba4e0>] ? manage_workers.isra.17+0x330/0x330
> [   33.884789]  [<ffffffff810c18c8>] kthread+0x108/0x110
> [   33.890441]  [<ffffffff810c17c0>] ? __init_kthread_worker+0x70/0x70
> [   33.897465]  [<ffffffff8208812c>] ret_from_fork+0x7c/0xb0
> [   33.903504]  [<ffffffff810c17c0>] ? __init_kthread_worker+0x70/0x70
> [   33.910508] Code: 89 85 b8 fe ff ff 49 8b 45 10 41 8b 75 0c 44 8b
> 50 08 44 8b 58 04 89 f0 48 c1 e0 0a 45 89 d1 49 8d 44 01 ff 48 89 c2
> 48 c1 fa 3f <49> f7 f9 31 d2 49 89 c1 89 f0 44 89 de 41 f7 f1 48 81 c6
> 00 02
> [   33.932375] RIP  [<ffffffff810dbf2c>] find_busiest_group+0x2ac/0x880
> [   33.939491]  RSP <ffff897c5ba8f9a8>
> [   33.943418] ---[ end trace 7a833c0cac54cac8 ]---

Hi, PeterZ,

This divide_by_zero could be workaround with attached patch.

Yinghai

[-- Attachment #2: sched_divide_by_zero_workaround.patch --]
[-- Type: text/x-patch, Size: 469 bytes --]

---
 kernel/sched/core.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6/kernel/sched/core.c
===================================================================
--- linux-2.6.orig/kernel/sched/core.c
+++ linux-2.6/kernel/sched/core.c
@@ -5737,6 +5737,9 @@ static int __sdt_alloc(const struct cpum
 			if (!sgp)
 				return -ENOMEM;
 
+			/* avoid divide-by-zero in sg_capacity() */
+			sgp->power_orig = 1;
+
 			*per_cpu_ptr(sdd->sgp, j) = sgp;
 		}
 	}