From: Linus Torvalds <torvalds@linux-foundation.org>
To: Tejun Heo <tj@kernel.org>
Cc: Ming Lei <ming.lei@canonical.com>,
Alex Riesen <raa.lkml@gmail.com>,
Alan Stern <stern@rowland.harvard.edu>,
Jens Axboe <axboe@kernel.dk>,
USB list <linux-usb@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: USB device cannot be reconnected and khubd "blocked for more than 120 seconds"
Date: Tue, 15 Jan 2013 16:36:34 -0800 [thread overview]
Message-ID: <CA+55aFzm4k2CyQ_mZVHyeasjw4ybqfO2SpJrZZNZeUsSW8PB=g@mail.gmail.com> (raw)
In-Reply-To: <20130115235043.GJ2668@htj.dyndns.org>
On Tue, Jan 15, 2013 at 3:50 PM, Tejun Heo <tj@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 same context as what *started* the module loading. A
module loader will request the module from user space, and then later
user space - through possibly a totally unrelated process - will
finish it. So there is no "myself". There's not even necessarily any
relationship that the kernel even knows about, because the module
loading request can have gone from usermode_helper over something like
dbus to systemd.
See?
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.
Linus
next prev parent reply other threads:[~2013-01-16 0:36 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-11 21:04 USB device cannot be reconnected and khubd "blocked for more than 120 seconds" Alex Riesen
2013-01-12 7:48 ` Alex Riesen
2013-01-12 9:18 ` Lan Tianyu
2013-01-12 17:37 ` Alan Stern
2013-01-12 19:39 ` Alex Riesen
2013-01-12 20:33 ` Alex Riesen
2013-01-12 22:52 ` Alan Stern
2013-01-13 12:09 ` Alex Riesen
2013-01-13 16:56 ` Alan Stern
2013-01-13 17:42 ` Alex Riesen
2013-01-13 19:16 ` Oliver Neukum
2013-01-14 2:39 ` Alan Stern
2013-01-14 16:43 ` Alex Riesen
2013-01-14 3:47 ` Ming Lei
2013-01-14 7:15 ` Ming Lei
2013-01-14 17:30 ` Linus Torvalds
2013-01-14 18:04 ` Alan Stern
2013-01-14 18:34 ` Linus Torvalds
2013-01-15 1:53 ` Ming Lei
2013-01-15 6:23 ` Ming Lei
2013-01-15 17:36 ` Linus Torvalds
2013-01-15 18:18 ` Linus Torvalds
2013-01-15 23:17 ` Tejun Heo
2013-01-15 18:20 ` Alan Stern
2013-01-15 18:39 ` Tejun Heo
2013-01-15 18:32 ` Tejun Heo
2013-01-15 20:18 ` Linus Torvalds
2013-01-15 23:50 ` Tejun Heo
2013-01-16 0:25 ` Arjan van de Ven
2013-01-16 0:35 ` Tejun Heo
2013-01-16 4:01 ` Alan Stern
2013-01-16 16:12 ` Tejun Heo
2013-01-16 17:01 ` Alan Stern
2013-01-16 17:37 ` Tejun Heo
2013-01-16 17:51 ` Alan Stern
2013-01-16 0:36 ` Linus Torvalds [this message]
2013-01-16 0:40 ` Linus Torvalds
2013-01-16 2:52 ` [PATCH] module, async: async_synchronize_full() on module init iff async is used Tejun Heo
2013-01-16 3:00 ` Linus Torvalds
2013-01-16 3:25 ` Tejun Heo
2013-01-16 3:37 ` Linus Torvalds
2013-01-16 16:22 ` Arjan van de Ven
2013-01-16 16:48 ` Tejun Heo
2013-01-16 17:03 ` Arjan van de Ven
2013-01-16 17:06 ` Linus Torvalds
2013-01-16 21:30 ` [PATCH 1/2] init, block: try to load default elevator module early during boot Tejun Heo
2013-01-17 18:05 ` Linus Torvalds
2013-01-17 18:38 ` Tejun Heo
2013-01-17 18:46 ` Linus Torvalds
2013-01-17 18:59 ` Tejun Heo
2013-01-17 19:00 ` Linus Torvalds
2013-01-18 1:24 ` [PATCH 1/3] workqueue: set PF_WQ_WORKER on rescuers Tejun Heo
2013-01-18 1:25 ` [PATCH 2/3] workqueue, async: implement work/async_current_func() Tejun Heo
2013-01-18 2:47 ` Linus Torvalds
2013-01-18 2:59 ` Tejun Heo
2013-01-18 3:04 ` Tejun Heo
2013-01-18 3:18 ` Linus Torvalds
2013-01-18 3:47 ` Tejun Heo
2013-01-18 22:08 ` [PATCH 1/5] workqueue: set PF_WQ_WORKER on rescuers Tejun Heo
2013-01-18 22:10 ` [PATCH 2/5] workqueue: rename kernel/workqueue_sched.h to kernel/workqueue_internal.h Tejun Heo
2013-01-18 22:11 ` [PATCH 3/5] workqueue: move struct worker definition to workqueue_internal.h Tejun Heo
2013-01-18 22:11 ` [PATCH 4/5] workqueue: implement current_is_async() Tejun Heo
2013-01-18 22:12 ` [PATCH 5/5] async, kmod: warn on synchronous request_module() from async workers Tejun Heo
2022-06-23 5:25 ` Saravana Kannan
2013-01-18 1:27 ` [PATCH 3/3] " Tejun Heo
2013-01-23 0:53 ` [PATCH v2 1/2] init, block: try to load default elevator module early during boot Tejun Heo
2013-01-16 21:31 ` [PATCH 2/2] block: don't request module during elevator init Tejun Heo
2013-01-23 0:51 ` [PATCH v2 " Tejun Heo
2013-01-16 3:30 ` [PATCH] module, async: async_synchronize_full() on module init iff async is used Ming Lei
2013-01-16 4:24 ` Rusty Russell
2013-01-16 11:36 ` Alex Riesen
2013-08-12 7:04 ` [3.8-rc3 -> 3.8-rc4 regression] " Jonathan Nieder
2013-08-12 15:09 ` Tejun Heo
2013-11-26 21:29 ` Josh Hunt
2013-11-26 21:53 ` Linus Torvalds
2013-11-26 22:12 ` Josh Hunt
2013-11-26 22:29 ` Tejun Heo
2013-12-03 14:28 ` Josh Hunt
2013-12-03 15:19 ` Tejun Heo
2013-12-04 23:01 ` Josh Hunt
2013-12-04 23:12 ` Tejun Heo
2013-11-26 22:30 ` Linus Torvalds
2013-01-16 0:44 ` USB device cannot be reconnected and khubd "blocked for more than 120 seconds" Tejun Heo
2013-01-16 17:19 ` [PATCH] async: fix __lowest_in_progress() Tejun Heo
2013-01-17 18:16 ` Linus Torvalds
2013-01-17 18:50 ` Tejun Heo
2013-01-23 0:15 ` [PATCH v2] " Tejun Heo
2013-01-23 0:22 ` Linus Torvalds
2013-01-16 3:05 ` USB device cannot be reconnected and khubd "blocked for more than 120 seconds" Ming Lei
2013-01-16 4:14 ` Linus Torvalds
2013-01-14 8:22 ` Oliver Neukum
2013-01-14 8:40 ` Ming Lei
2013-01-12 19:56 ` Alex Riesen
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