On Wed, 23 May 2007 10:47:04 -0400 (EDT) Alan Stern <stern@rowland.harvard.edu> wrote:

quoted text
> On Wed, 23 May 2007, Rafael J. Wysocki wrote:
> 
> > On Wednesday, 23 May 2007 09:48, Andrew Morton wrote:
> > > On Wed, 23 May 2007 00:42:33 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> > > 
> > > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc2/2.6.22-rc2-mm1/
> > > 
> > > This is intermittently getting resume-from-RAM failures.  It is not
> > > sufficiently repeatable to be able to bisect.
> > > 
> > > [ 1381.119362] PM: Preparing system for mem sleep
> > > [ 2331.798452] Stopping tasks ... 
> > > [ 2351.760431] Stopping kernel threads timed out after 20 seconds (2 tasks refusing to freeze):
> > > [ 2351.762385]  ksuspend_usbd
> > > [ 2351.764374]  khubd
> > > [ 2351.766338] Restarting tasks ... done.
> > 
> > Hmm, that seems to be related to usb-fix-suspend-to-ram.patch (probably one of
> > the threads is waiting for a completion by some other thread that has been
> > frozen already).
> 
> 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.
> 

We can do this?

--- a/kernel/power/process.c~freezer-run-show_state-when-freezing-times-out
+++ a/kernel/power/process.c
@@ -157,6 +157,7 @@ static unsigned int try_to_freeze_tasks(
 				freeze_user_space ? "user space processes" :
 					"kernel threads",
 				TIMEOUT / HZ, todo);
+		show_state();
 		read_lock(&tasklist_lock);
 		do_each_thread(g, p) {
 			if (freeze_user_space && !is_user_space(p))
_

but it generates an awful lot of output.

The trace is at http://userweb.kernel.org/~akpm/tasks.txt.  Interesting
bits are

[  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]  =======================


[  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

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