On 05/23, Andrew Morton wrote:
>
> On Wed, 23 May 2007 10:47:04 -0400 (EDT) Alan Stern <[email protected]> wrote:
>
> > Is it possible to get an Alt-SysRq-T stack trace during those 20
> > seconds? Knowing what those threads are waiting for would be a big
> > help.
>
> [ 144.201264] khubd D 00400005 0 160 2 (L-TLB)
> [ 144.204358] c207fe78 00000046 90399a85 00400005 00000246 c207fe60 c25b0cc4 c206f4cc
> [ 144.204539] 00000286 00000000 769e4cea 0040000a 90399a85 00400005 c32713c0 c207fed4
> [ 144.207754] 00000001 c207fe94 c207febc c02e8e1b 00000000 00000000 00000000 00000000
> [ 144.210934] Call Trace:
> [ 144.217012] [<c02e8e1b>] wait_for_completion+0x68/0x91
> [ 144.220090] [<c011824f>] default_wake_function+0x0/0x9
> [ 144.223158] [<c0127a41>] flush_cpu_workqueue+0x4d/0x55
> [ 144.226223] [<c0127a69>] wq_barrier_func+0x0/0x8
> [ 144.229269] [<c026343d>] usb_release_dev+0x28/0x63
> [ 144.232340] [<c0233011>] device_release+0x37/0x7c
> [ 144.235431] [<c01cb6c7>] kobject_cleanup+0x3d/0x54
> [ 144.238520] [<c01cb6de>] kobject_release+0x0/0x8
> [ 144.241631] [<c01cc2a7>] kref_put+0x75/0x82
> [ 144.244699] [<c0265482>] hub_thread+0x376/0xa74
> [ 144.247768] [<c01180c2>] pick_next_task_fair+0xf2/0x12a
> [ 144.250815] [<c0116af1>] __wake_up_common+0x31/0x4f
> [ 144.253864] [<c012a259>] autoremove_wake_function+0x0/0x35
> [ 144.256902] [<c026510c>] hub_thread+0x0/0xa74
> [ 144.259944] [<c012a102>] kthread+0x36/0x5c
> [ 144.262891] [<c012a0cc>] kthread+0x0/0x5c
> [ 144.265757] [<c010464b>] kernel_thread_helper+0x7/0x10
> [ 144.268716] =======================
Looks like usb_release_dev() does flush_workqueue() under usb_lock_device().
Is it possible? If yes, flush_workqueue() stalls because this lock is need
to finish the execution of ->wakeup_work (below).
usb_release_dev:
#ifdef CONFIG_USB_SUSPEND
cancel_delayed_work(&udev->autosuspend);
flush_workqueue(ksuspend_usb_wq);
#endif
What is the reason for flush_workqueue() here? _IF_ it is only needed to flush
->autosuspend, we can use cancel_rearming_delayed_work(&udev->autosuspend).
> [ 144.137704] ksuspend_usbd D 00400005 0 157 2 (L-TLB)
> [ 144.140830] c2085f18 00000046 9072767a 00400005 c20626f0 c010449b c3182118 c206288c
> [ 144.141011] c3182120 c3182120 76d728df 0040000a 9072767a 00400005 c3271200 c3182118
> [ 144.144263] c3182120 00000246 c20626f0 c02ea1c9 00000000 00000000 00000000 00000000
> [ 144.147576] Call Trace:
> [ 144.153929] [<c010449b>] common_interrupt+0x23/0x28
> [ 144.157245] [<c02ea1c9>] __down+0xba/0xc6
> [ 144.160528] [<c011824f>] default_wake_function+0x0/0x9
> [ 144.163832] [<c02664fc>] hcd_resume_work+0x0/0x43
> [ 144.167126] [<c02e9fd3>] __down_failed+0x7/0xc
> [ 144.170372] [<c0266518>] hcd_resume_work+0x1c/0x43
> [ 144.173603] [<c01278cf>] run_workqueue+0x6d/0xdf
> [ 144.176780] [<c0127b4c>] worker_thread+0x0/0xd0
> [ 144.179885] [<c0127b4c>] worker_thread+0x0/0xd0
> [ 144.182930] [<c0127c12>] worker_thread+0xc6/0xd0
> [ 144.185964] [<c012a259>] autoremove_wake_function+0x0/0x35
> [ 144.189056] [<c012a102>] kthread+0x36/0x5c
> [ 144.192118] [<c012a0cc>] kthread+0x0/0x5c
> [ 144.195153] [<c010464b>] kernel_thread_helper+0x7/0x10
Oleg.
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