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Message-ID: <252c5d0b-0195-0a56-e236-21e8da449071@oracle.com>
Date: Tue, 24 Jan 2017 08:47:15 -0500
From: Boris Ostrovsky <boris.ostrovsky@...cle.com>
To: Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v3 3/3] xen: optimize xenbus driver for multiple
concurrent xenstore accesses
On 01/23/2017 01:59 PM, Boris Ostrovsky wrote:
> On 01/23/2017 05:09 AM, Juergen Gross wrote:
>> Handling of multiple concurrent Xenstore accesses through xenbus driver
>> either from the kernel or user land is rather lame today: xenbus is
>> capable to have one access active only at one point of time.
>>
>>
This patch appears to break save/restore:
[ 39.979281] Freezing user space processes ... (elapsed 0.000 seconds)
done.
[ 39.981347] Freezing remaining freezable tasks ... (elapsed 0.000
seconds) done.
[ 39.983853] PM: freeze of devices complete after 0.537 msecs
[ 39.984955] suspending xenstore...
[ 246.751144] INFO: task xenwatch:35 blocked for more than 120 seconds.
[ 246.752286] Not tainted 4.10.0-rc5upstream-00311-g3eda026 #2
[ 246.753378] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 246.754489] xenwatch D12056 35 2 0x00000000
[ 246.755624] Call Trace:
[ 246.756732] __schedule+0x225/0x6f0
[ 246.757834] schedule+0x3c/0xb0
[ 246.758918] xs_suspend+0x84/0xc0
[ 246.759983] ? woken_wake_function+0x10/0x10
[ 246.761039] do_suspend+0x52/0x190
[ 246.762079] ? xenbus_transaction_end+0x2f/0x40
[ 246.763097] shutdown_handler+0xfc/0x130
[ 246.764086] xenwatch_thread+0xaa/0x150
[ 246.765076] ? woken_wake_function+0x10/0x10
[ 246.766042] ? schedule+0x3c/0xb0
[ 246.766951] ? _raw_spin_unlock_irqrestore+0x15/0x20
[ 246.767869] ? xenbus_printf+0xa0/0xa0
[ 246.768603] kthread+0x109/0x140
[ 246.769057] ? __kthread_init_worker+0x30/0x30
[ 246.769514] ret_from_fork+0x2c/0x40
[ 246.769963] NMI backtrace for cpu 1
[ 246.770422] CPU: 1 PID: 322 Comm: khungtaskd Not tainted
4.10.0-rc5upstream-00311-g3eda026 #2
[ 246.770898] Call Trace:
[ 246.771366] dump_stack+0x67/0x98
[ 246.771413] ? x86_vector_alloc_irqs+0x111/0x1a0
[ 246.771413] nmi_cpu_backtrace+0xae/0xb0
[ 246.771413] ? hw_nmi_get_sample_period+0x20/0x20
[ 246.771413] nmi_trigger_cpumask_backtrace+0x126/0x160
[ 246.771413] arch_trigger_cpumask_backtrace+0x14/0x20
[ 246.771413] watchdog+0x3bf/0x470
[ 246.771413] ? reset_hung_task_detector+0x20/0x20
[ 246.771413] ? schedule+0x3c/0xb0
[ 246.771413] ? _raw_spin_unlock_irqrestore+0x15/0x20
[ 246.771413] ? reset_hung_task_detector+0x20/0x20
[ 246.771413] kthread+0x109/0x140
[ 246.771413] ? proc_cap_handler+0x1a0/0x1a0
[ 246.771413] ? __kthread_init_worker+0x30/0x30
[ 246.771413] ? proc_cap_handler+0x1a0/0x1a0
[ 246.771413] ? proc_cap_handler+0x1a0/0x1a0
[ 246.771413] ret_from_fork+0x2c/0x40
[ 246.778690] Sending NMI from CPU 1 to CPUs 0:
[ 246.779265] NMI backtrace for cpu 0
[ 246.779609] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
4.10.0-rc5upstream-00311-g3eda026 #2
[ 246.779961] task: ffffffff81e11500 task.stack: ffffffff81e00000
[ 246.780257] RIP: e030:xen_hypercall_sched_op+0xa/0x20
[ 246.780257] RSP: e02b:ffffffff81e03dd0 EFLAGS: 00000246
[ 246.780257] RAX: 0000000000000000 RBX: ffffffff81e11500 RCX:
ffffffff810013aa
[ 246.780257] RDX: 0000000000000001 RSI: deadbeefdeadf00d RDI:
deadbeefdeadf00d
[ 246.780257] RBP: ffffffff81e03de8 R08: 0100000000000000 R09:
ffff88003f212940
[ 246.780257] R10: 0000000000000000 R11: 0000000000000246 R12:
0000000000000000
[ 246.780257] R13: 0000000000000000 R14: ffffffff81e11502 R15:
ffffffff81e11500
[ 246.780257] FS: 00007f53626e9700(0000) GS:ffff88003f200000(0000)
knlGS:0000000000000000
[ 246.780257] CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 246.780257] CR2: ffffffffff600400 CR3: 0000000007616000 CR4:
0000000000042660
[ 246.780257] Call Trace:
[ 246.780257] ? xen_safe_halt+0x10/0x20
[ 246.780257] default_idle+0x1d/0x100
[ 246.780257] arch_cpu_idle+0xa/0x10
[ 246.780257] default_idle_call+0x1e/0x30
[ 246.780257] do_idle+0x17c/0x250
[ 246.780257] cpu_startup_entry+0x1d/0x20
[ 246.780257] rest_init+0x80/0x90
[ 246.780257] start_kernel+0x483/0x490
[ 246.780257] ? set_init_arg+0x5e/0x5e
[ 246.780257] x86_64_start_reservations+0x2a/0x2c
[ 246.780257] xen_start_kernel+0x51b/0x51d
[ 246.780257] Code: cc 51 41 53 b8 1c 00 00 00 0f 05 41 5b 59 c3 cc cc
cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 51 41 53 b8 1d 00 00 00
0f 05 <41> 5b 59 c3 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
[ 246.952336] Kernel panic - not syncing: hung_task: blocked tasks
[ 246.952818] CPU: 1 PID: 322 Comm: khungtaskd Not tainted
4.10.0-rc5upstream-00311-g3eda026 #2
[ 246.953318] Call Trace:
[ 246.953318] dump_stack+0x67/0x98
[ 246.953318] panic+0xcd/0x22c
[ 246.953318] ? find_next_bit+0xb/0x10
[ 246.953318] watchdog+0x3cd/0x470
[ 246.953318] ? reset_hung_task_detector+0x20/0x20
[ 246.953318] ? schedule+0x3c/0xb0
[ 246.953318] ? _raw_spin_unlock_irqrestore+0x15/0x20
[ 246.953318] ? reset_hung_task_detector+0x20/0x20
[ 246.953318] kthread+0x109/0x140
[ 246.953318] ? proc_cap_handler+0x1a0/0x1a0
[ 246.953318] ? __kthread_init_worker+0x30/0x30
[ 246.953318] ? proc_cap_handler+0x1a0/0x1a0
[ 246.953318] ? proc_cap_handler+0x1a0/0x1a0
[ 246.953318] ret_from_fork+0x2c/0x40
[ 246.953318] Kernel Offset: disabled
-bash-4.1# xl destroy bootstrap-x86_64
-boris
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