linux-kernel - Re: [lkp-robot] [lib/rbtree] c21f87074d: WARNING:at_kernel/events/core.c:#perf_swevent

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Date:   Fri, 17 Nov 2017 14:05:22 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     kernel test robot <xiaolong.ye@...el.com>
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Davidlohr Bueso <dbueso@...e.de>,
        Fengguang Wu <fengguang.wu@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...org,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...e.hu>
Subject: Re: [lkp-robot] [lib/rbtree]  c21f87074d:
 WARNING:at_kernel/events/core.c:#perf_swevent_add

On Fri, 17 Nov 2017 10:26:27 +0800 kernel test robot <xiaolong.ye@...el.com> wrote:

> 
> FYI, we noticed the following commit (built with gcc-6):
> 
> commit: c21f87074dc24c9e5a13dc63918b2d30891d190f ("lib/rbtree-test: lower default params")
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> 
> in testcase: boot

Looks like a false positive to me.  That commit fiddles with
lib/interval_tree_test.c and lib/rbtree_test.c.

> on test machine: qemu-system-x86_64 -enable-kvm -smp 2 -m 512M
> 
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> 
> 
> +---------------------------------------------------+------------+------------+
> |                                                   | ced2d43150 | c21f87074d |
> +---------------------------------------------------+------------+------------+
> | boot_successes                                    | 3          | 2          |
> | boot_failures                                     | 13         | 14         |
> | BUG:kernel_hang_in_test_stage                     | 13         | 14         |
> | WARNING:at_kernel/events/core.c:#perf_swevent_add | 0          | 14         |
> | RIP:perf_swevent_add                              | 0          | 14         |
> +---------------------------------------------------+------------+------------+
> 
> 
> 
> [   14.436079] WARNING: CPU: 0 PID: 412 at kernel/events/core.c:7735 perf_swevent_add+0x90/0xe0
> [   14.437206] Modules linked in:
> [   14.437548] CPU: 0 PID: 412 Comm: trinity-main Not tainted 4.14.0-rc8-00303-gc21f870 #2
> [   14.438407] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> [   14.439350] task: ffff88001c554fc0 task.stack: ffff88001ef30000
> [   14.440006] RIP: 0010:perf_swevent_add+0x90/0xe0
> [   14.440546] RSP: 0018:ffff88001ef33c28 EFLAGS: 00010096
> [   14.441095] RAX: 00000000ffffffff RBX: ffff88001e00d3d8 RCX: 0000000000000002
> [   14.441876] RDX: ffff88001c554fc0 RSI: 0000000000000001 RDI: ffff88001e00d3d8
> [   14.442652] RBP: 0000000000000009 R08: 00000004e4fe313d R09: 0000000098260c66
> [   14.443429] R10: ffff88001ef33c58 R11: 0000000000000002 R12: 0000000000000000
> [   14.444187] R13: 0000000000000000 R14: 0000000000000001 R15: ffff88001ed7b508
> [   14.444931] FS:  00007ff942e15700(0000) GS:ffffffff81c29000(0000) knlGS:0000000000000000
> [   14.445780] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   14.446404] CR2: 0000000001697a28 CR3: 000000001dfbb000 CR4: 00000000000006b0
> [   14.447158] Call Trace:
> [   14.447468]  event_sched_in+0xee/0x240
> [   14.447884]  group_sched_in+0x5f/0x1a0
> [   14.448298]  ctx_sched_in+0x363/0x3ca
> [   14.448758]  perf_event_sched_in+0x66/0x6d
> [   14.449314]  ctx_resched+0x9d/0xaf
> [   14.449716]  __perf_install_in_context+0x104/0x137
> [   14.450225]  remote_function+0x1e/0x43
> [   14.450710]  ? rb_free_rcu+0x13/0x13
> [   14.451109]  smp_call_function_single+0x39/0x4a
> [   14.451644]  ? __perf_event_enable+0x182/0x182
> [   14.452111]  task_function_call+0x57/0x95
> [   14.452605]  ? __perf_event_enable+0x182/0x182
> [   14.453094]  perf_install_in_context+0xbe/0x128
> [   14.453580]  SyS_perf_event_open+0xea0/0x11bf
> [   14.454050]  entry_SYSCALL_64_fastpath+0x1e/0xad
> [   14.454606] RIP: 0033:0x7ff94292a6d9
> [   14.455002] RSP: 002b:00007ffdb9512bb8 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
> [   14.455852] RAX: ffffffffffffffda RBX: 0000000001695a20 RCX: 00007ff94292a6d9
> [   14.456618] RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 000000000141c000
> [   14.457378] RBP: 0000000000002011 R08: 0000000000000003 R09: 0000000000000004
> [   14.458121] R10: ffffffffffffffff R11: 0000000000000246 R12: 00000000000225f1
> [   14.458919] R13: 0000000000002000 R14: 0000000001695a10 R15: 00000000000005f0
> [   14.459751] Code: 89 ed 49 bc eb 83 b5 80 46 86 c8 61 4c 09 f5 49 0f af ec e8 41 a0 fe ff 48 c1 ed 38 4d 8d 64 ed 00 4d 85 e4 75 0e e8 2e a0 fe ff <0f> ff bb ea ff ff ff eb 37 e8 20 a0 fe ff 49 8b 6c ed 00 4c 8d 
> [   14.461842] ---[ end trace 43d85185818af4ed ]---
> 

that's the WARN_ON_ONCE() in

static int perf_swevent_add(struct perf_event *event, int flags)
{
	struct swevent_htable *swhash = this_cpu_ptr(&swevent_htable);
	struct hw_perf_event *hwc = &event->hw;
	struct hlist_head *head;

	if (is_sampling_event(event)) {
		hwc->last_period = hwc->sample_period;
		perf_swevent_set_period(event);
	}

	hwc->state = !(flags & PERF_EF_START);

	head = find_swevent_head(swhash, event);
	if (WARN_ON_ONCE(!head))
		return -EINVAL;

	hlist_add_head_rcu(&event->hlist_entry, head);
	perf_event_update_userpage(event);

	return 0;
}