Hello, Alan.
On Tue, Jan 15, 2013 at 11:01:15PM -0500, Alan Stern wrote:
The current domain implementation is somewhere inbetween. It's not
completely simplistic system and at the same time not developed enough
to do properly stacked flushing.
I like your idea of chronological
On Wed, 16 Jan 2013, Tejun Heo wrote:
Hello, Alan.
On Tue, Jan 15, 2013 at 11:01:15PM -0500, Alan Stern wrote:
The current domain implementation is somewhere inbetween. It's not
completely simplistic system and at the same time not developed enough
to do properly stacked flushing.
Hello, Alan.
On Wed, Jan 16, 2013 at 12:01:53PM -0500, Alan Stern wrote:
The problem here is that flush everything which comes before me is
used to order async jobs. e.g. after async jobs probe the hardware
they order themselves by flushing before registering them, so unless
I don't
On Wed, 16 Jan 2013, Tejun Heo wrote:
Hello, Alan.
On Wed, Jan 16, 2013 at 12:01:53PM -0500, Alan Stern wrote:
The problem here is that flush everything which comes before me is
used to order async jobs. e.g. after async jobs probe the hardware
they order themselves by flushing
[ Added Tejun to the discussion, since he's the async go-to-guy ]
On Mon, Jan 14, 2013 at 10:23 PM, Ming Lei ming@canonical.com wrote:
But I have another idea to address the problem, and let module code call
async_synchronize_full() only if the module requires that explicitly, so how
On Tue, Jan 15, 2013 at 9:36 AM, Linus Torvalds
torva...@linux-foundation.org wrote:
This kind of let's randomly encourage people to write subtly buggy
code that has magical timing dependencies, so that the developer won't
likely even see it because he has fast disks etc code is totally
On Tue, 15 Jan 2013, Linus Torvalds wrote:
Tejun, comments? You can see the whole thread on lkml, but the basic
problem is that the module loading doing the unconditional
async_synchronize_full() has caused problems, because we have
- load module A
- module A does per-controller async
Hello, Linus.
On Tue, Jan 15, 2013 at 09:36:57AM -0800, Linus Torvalds wrote:
Tejun, comments? You can see the whole thread on lkml, but the basic
problem is that the module loading doing the unconditional
async_synchronize_full() has caused problems, because we have
- load module A
-
Hello, Alan.
On Tue, Jan 15, 2013 at 01:20:58PM -0500, Alan Stern wrote:
It may not be so easy. When the SCSI async thread probes the new disk,
it has to do I/O. So it needs to use a scheduler.
But maybe it could use a built-in trivial scheduler until the proper
one is loaded. Then the
On Tue, Jan 15, 2013 at 10:32 AM, Tejun Heo t...@kernel.org wrote:
I think the root problem here, apart from request_module() from block
- which is a bit nasty but making that part completely async would too
be quite nasty albeit in a different way - is that
async_synchronize_full() is way
Hello, Linus
Will continue on another reply but this one is relevant so...
On Tue, Jan 15, 2013 at 10:18:45AM -0800, Linus Torvalds wrote:
Tejun, is there a good way for code to see I'm running in async
context? Then we could do something like
Almost. With a bit of modification we can ask
cc'ing Arjan. Arjan, the original thread can be read from
http://thread.gmane.org/gmane.linux.kernel/1420814
Hello, again.
On Tue, Jan 15, 2013 at 12:18:01PM -0800, Linus Torvalds wrote:
I think that is a good solution if it works, but look out: we need to
synchronize across *all* domains,
For now, I'm gonna implement simple I'm not gonna wait for myself
self-deadlock avoidance. If this needs any more sophistication, I
think we better reimplement it so that we can explicitly match up and
track who's gonna wait for what instead of throwing everything into a
single cookie space
Hello, Arjan.
On Tue, Jan 15, 2013 at 04:25:54PM -0800, Arjan van de Ven wrote:
async fundamentally had the concept of a monotonic increasing number,
and that you could always wait for everyone before me.
then people (like me) wanted exceptions to what everyone means ;-(
I'm ok with going
On Tue, Jan 15, 2013 at 3:50 PM, Tejun Heo t...@kernel.org wrote:
For now, I'm gonna implement simple I'm not gonna wait for myself
self-deadlock avoidance.
You can't really do that. Or rather, it won't *help*.
The thing is, the module loading in particular is not necessarily
happening in the
On Tue, Jan 15, 2013 at 4:36 PM, Linus Torvalds
torva...@linux-foundation.org wrote:
There's a reason I asked for a warning for this. Or the let's flag
the current thread if it ever started anything asynchronous. Because
it's complicated.
Btw, the sequence counter (that is *not* taking
On Tue, Jan 15, 2013 at 04:36:34PM -0800, Linus Torvalds wrote:
The thing is, the module loading in particular is not necessarily
happening in the same context as what *started* the module loading. A
module loader will request the module from user space, and then later
user space - through
On Wed, Jan 16, 2013 at 1:36 AM, Linus Torvalds
torva...@linux-foundation.org wrote:
Because it's not just sd.c that uses async_schedule(), and would need
the async synchronize. It's floppy.c, it's generic scsi scanning (so
scsi tapes etc), and it's libata-core.c.
As discussed previously,
On Tue, 15 Jan 2013, Tejun Heo wrote:
Hello, Arjan.
On Tue, Jan 15, 2013 at 04:25:54PM -0800, Arjan van de Ven wrote:
async fundamentally had the concept of a monotonic increasing number,
and that you could always wait for everyone before me.
then people (like me) wanted exceptions to
On Monday 14 January 2013 11:47:57 Ming Lei wrote:
[ 181.175323] echo 0 /proc/sys/kernel/hung_task_timeout_secs
disables this message.
[ 181.183624] modprobeD c04f1920 0 2462 2461 0x
[ 181.183685] [c04f1920] (__schedule+0x5fc/0x6d4) from [c005eba4]
On Mon, Jan 14, 2013 at 4:22 PM, Oliver Neukum oli...@neukum.org wrote:
OK, your trace is totally different. If your hangs are related, as is likely,
my explanation goes out of the window.
If I run 'shutdown' after unplugging usb storage device, another hang trace
same with Alex's can be
On Mon, Jan 14, 2013 at 3:39 AM, Alan Stern st...@rowland.harvard.edu wrote:
On Sun, 13 Jan 2013, Oliver Neukum wrote:
This is not a USB problem. You need to involve the SCSI people.
khubd just stops working because disconnects are processed
in its context and the removal deadlocks.
The why
On Sun, Jan 13, 2013 at 11:15 PM, Ming Lei ming@canonical.com wrote:
The deadlock problem is caused by calling request_module() inside
async function of do_scan_async(), and it was introduced by Linus's
below commit:
commit d6de2c80e9d758d2e36c21699117db6178c0f517
Author: Linus Torvalds
On Mon, 14 Jan 2013, Linus Torvalds wrote:
- from view of driver, introducing async_synchronize_full() after
do_one_initcall() inside do_init_module() is like a sync probe
for drivers built as module, and cause this kind of deadlock easily.
So could we revert the commit and fix the
On Mon, Jan 14, 2013 at 10:04 AM, Alan Stern st...@rowland.harvard.edu wrote:
How about skipping that call if the current thread is one of the async
helpers? Is it possible to detect when that happens?
Or maybe such a check should go inside async_synchronize_full() itself.
Do we have some
On Tue, Jan 15, 2013 at 1:30 AM, Linus Torvalds
torva...@linux-foundation.org wrote:
On Sun, Jan 13, 2013 at 11:15 PM, Ming Lei ming@canonical.com wrote:
The deadlock problem is caused by calling request_module() inside
async function of do_scan_async(), and it was introduced by Linus's
On Tue, Jan 15, 2013 at 9:53 AM, Ming Lei ming@canonical.com wrote:
I will try to figure out one patch to address the scsi block async probe
issue first, and see if it can fix the problem by moving add_disk()
into sd_probe()
and calling async_synchronize_full_domain(scsi_sd_probe_domain)
On Sat, Jan 12, 2013 at 11:52 PM, Alan Stern st...@rowland.harvard.edu wrote:
On Sat, 12 Jan 2013, Alex Riesen wrote:
Now, who would be interested to handle this kind of misconfiguration ...
So the whole thing was a false alarm?
Yes, almost. What about khubd hanging when machine is shutdown?
On Sun, 13 Jan 2013, Alex Riesen wrote:
On Sat, Jan 12, 2013 at 11:52 PM, Alan Stern st...@rowland.harvard.edu
wrote:
On Sat, 12 Jan 2013, Alex Riesen wrote:
Now, who would be interested to handle this kind of misconfiguration ...
So the whole thing was a false alarm?
Yes, almost.
On Sun, Jan 13, 2013 at 5:56 PM, Alan Stern st...@rowland.harvard.edu wrote:
On Sun, 13 Jan 2013, Alex Riesen wrote:
Yes, almost. What about khubd hanging when machine is shutdown?
What about it? I have trouble understanding all the descriptions you
have provided so far, because you talk
On Sunday 13 January 2013 18:42:49 Alex Riesen wrote:
On Sun, Jan 13, 2013 at 5:56 PM, Alan Stern st...@rowland.harvard.edu wrote:
On Sun, 13 Jan 2013, Alex Riesen wrote:
Yes, almost. What about khubd hanging when machine is shutdown?
What about it? I have trouble understanding all the
On Sun, 13 Jan 2013, Oliver Neukum wrote:
On Sunday 13 January 2013 18:42:49 Alex Riesen wrote:
On Sun, Jan 13, 2013 at 5:56 PM, Alan Stern st...@rowland.harvard.edu
wrote:
On Sun, 13 Jan 2013, Alex Riesen wrote:
Yes, almost. What about khubd hanging when machine is shutdown?
On Mon, Jan 14, 2013 at 1:42 AM, Alex Riesen raa.l...@gmail.com wrote:
1. Compile a kernel with deadline elevator as module
2. Boot into it, make sure the elevator is selected
(I used elevator=deadline in the kernel command line)
3. Insert a FAT formatted mass storage device in an USB2 port
On 2013年1月12日 15:48:59, Alex Riesen wrote:
On Fri, Jan 11, 2013 at 10:04 PM, Alex Riesen raa.l...@gmail.com wrote:
Hi,
the USB stick (an Cruzer Titanium 2GB) was not recognized at any of
the USB ports of this system (an System76 lemu4 laptop, XHCI device)
after it was removed. If I attempt to
On Sat, 12 Jan 2013, Alex Riesen wrote:
On Fri, Jan 11, 2013 at 10:04 PM, Alex Riesen raa.l...@gmail.com wrote:
Hi,
the USB stick (an Cruzer Titanium 2GB) was not recognized at any of
the USB ports of this system (an System76 lemu4 laptop, XHCI device)
after it was removed. If I
On Sat, Jan 12, 2013 at 6:37 PM, Alan Stern st...@rowland.harvard.edu wrote:
On Sat, 12 Jan 2013, Alex Riesen wrote:
One more detail: I usually use the noop elevator. That time it was
the deadline. And I just reproduced it easily with deadline.
I doubt the elevator has anything to do with
On Sat, Jan 12, 2013 at 6:37 PM, Alan Stern st...@rowland.harvard.edu wrote:
On Sat, 12 Jan 2013, Alex Riesen wrote:
On Fri, Jan 11, 2013 at 10:04 PM, Alex Riesen raa.l...@gmail.com wrote:
the USB stick (an Cruzer Titanium 2GB) was not recognized at any of
the USB ports of this system (an
On Sat, Jan 12, 2013 at 8:39 PM, Alex Riesen raa.l...@gmail.com wrote:
On Sat, Jan 12, 2013 at 6:37 PM, Alan Stern st...@rowland.harvard.edu wrote:
On Sat, 12 Jan 2013, Alex Riesen wrote:
One more detail: I usually use the noop elevator. That time it was
the deadline. And I just reproduced it
On Sat, 12 Jan 2013, Alex Riesen wrote:
On Sat, Jan 12, 2013 at 8:39 PM, Alex Riesen raa.l...@gmail.com wrote:
On Sat, Jan 12, 2013 at 6:37 PM, Alan Stern st...@rowland.harvard.edu
wrote:
On Sat, 12 Jan 2013, Alex Riesen wrote:
One more detail: I usually use the noop elevator. That time
On Fri, Jan 11, 2013 at 10:04 PM, Alex Riesen raa.l...@gmail.com wrote:
Hi,
the USB stick (an Cruzer Titanium 2GB) was not recognized at any of
the USB ports of this system (an System76 lemu4 laptop, XHCI device)
after it was removed. If I attempt to insert it again in any of the
ports (one
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