All of lore.kernel.org
 help / color / mirror / Atom feed
From: Hillf Danton <hdanton@sina.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org, USB list <linux-usb@vger.kernel.org>
Subject: Re: Converting dev->mutex into dev->spinlock ?
Date: Sun,  5 Feb 2023 08:21:56 +0800	[thread overview]
Message-ID: <20230205002156.1071-1-hdanton@sina.com> (raw)
In-Reply-To: <Y958hOvtqq7Uiu0G@rowland.harvard.edu>

On Sat, 4 Feb 2023 10:40:52 -0500 Alan Stern <stern@rowland.harvard.edu>
> On Sun, Feb 05, 2023 at 12:30:07AM +0900, Tetsuo Handa wrote:
> > On 2023/02/05 0:12, Alan Stern wrote:
> > >>  it would solve many deadlocks in driver code if you can update
> > > 
> > > What deadlocks?  If there are so many deadlocks floating around in 
> > > driver code, why haven't we heard about them before now?
> > 
> > Since dev->mutex is hidden from lockdep checks, nobody can see lockdep warnings.
> > syzbot is reporting real deadlocks without lockdep warnings, for the fundamental
> > problem you mentioned in https://lkml.kernel.org/r/Pine.LNX.4.44L0.0804171117450.18040-100000@iolanthe.rowland.org
> > is remaining. I'm suggesting you that now is time to address this fundamental problem.
> 
> Maybe so.  But the place to address it is inside lockdep, not in the 
> driver core.
> 
> > >> (by e.g. replacing dev->mutex with dev->spinlock and dev->atomic_flags).
> > >> But I'm not familiar enough to propose such change...
> > > 
> > > Such a change cannot be made.  Consider this: Driver callbacks often
> > > need to sleep.  But when a thread holds a spinlock, it is not allowed to 
> > > sleep.  Therefore driver callbacks must not be invoked while a spinlock 
> > > is held.
> > 
> > What I'm suggesting is "Do not call driver callbacks with dev->mutex held,
> > by rewriting driver core code".
> 
> That cannot be done.  The only possible solution is to teach lockdep how 
> to handle recursive locking structures.

It works in dcache - see the slow path in dentry_kill() for instance.

Hillf


      reply	other threads:[~2023-02-05  0:22 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-04 13:32 Converting dev->mutex into dev->spinlock ? Tetsuo Handa
2023-02-04 13:47 ` Greg Kroah-Hartman
2023-02-04 14:21   ` Tetsuo Handa
2023-02-04 14:34     ` Greg Kroah-Hartman
2023-02-04 15:16       ` Tetsuo Handa
2023-02-04 15:34     ` Alan Stern
2023-02-04 16:12       ` Tetsuo Handa
2023-02-04 16:27         ` Alan Stern
2023-02-04 17:09           ` Tetsuo Handa
2023-02-04 20:01             ` Alan Stern
2023-02-04 20:14               ` Linus Torvalds
2023-02-05  1:23                 ` Alan Stern
2023-02-06 14:13                   ` Tetsuo Handa
2023-02-06 15:45                     ` Alan Stern
2023-02-07 13:07                       ` Tetsuo Handa
2023-02-07 17:46                         ` Alan Stern
2023-02-07 22:17                           ` Tetsuo Handa
2023-02-08  0:34                             ` Alan Stern
     [not found]                             ` <20230208080739.1649-1-hdanton@sina.com>
2023-02-08 10:30                               ` [PATCH] drivers/core: Replace lockdep_set_novalidate_class() with unique class keys Tetsuo Handa
2023-02-08 15:07                                 ` Alan Stern
2023-02-09  0:22                                   ` Tetsuo Handa
2023-02-09  0:46                                     ` Linus Torvalds
2023-02-09  1:50                                       ` Tetsuo Handa
2023-02-09  2:26                                     ` Alan Stern
2023-02-11  2:04                                       ` Tetsuo Handa
2023-02-11 21:41                                         ` [PATCH RFC] " Alan Stern
2023-02-11 21:51                                           ` Linus Torvalds
2023-02-11 23:06                                             ` Kent Overstreet
2023-02-11 23:08                                               ` Kent Overstreet
2023-02-11 23:24                                               ` Kent Overstreet
2023-02-12  2:40                                                 ` Alan Stern
2023-02-12  2:46                                                   ` Kent Overstreet
2023-02-12  3:03                                                     ` Alan Stern
2023-02-12  3:10                                                       ` Kent Overstreet
2023-02-12 15:23                                                         ` Alan Stern
2023-02-12 19:14                                                           ` Kent Overstreet
2023-02-12 20:19                                                             ` Alan Stern
2023-02-12 20:51                                                               ` Kent Overstreet
2023-02-13  1:23                                                                 ` Alan Stern
2023-02-13  2:21                                                                   ` Kent Overstreet
2023-02-13 15:25                                                                     ` Alan Stern
2023-02-13  9:29                                                                 ` Peter Zijlstra
2023-02-13  9:27                                                               ` Peter Zijlstra
2023-02-13 15:28                                                                 ` Alan Stern
2023-02-13 16:36                                                                   ` Peter Zijlstra
2023-02-13  9:24                                                           ` Peter Zijlstra
2023-02-13 15:25                                                             ` Alan Stern
2023-02-13 16:29                                                               ` Peter Zijlstra
2023-02-14  1:51                                                                 ` Boqun Feng
2023-02-14  1:53                                                                   ` Boqun Feng
2023-02-14  2:03                                                                   ` Alan Stern
2023-02-14  2:09                                                                     ` Boqun Feng
     [not found]                                                                     ` <20230214052733.3354-1-hdanton@sina.com>
2023-02-14  5:55                                                                       ` Boqun Feng
2023-02-14 10:48                                                                   ` Peter Zijlstra
2023-02-14 16:22                                                                     ` Boqun Feng
2023-02-15 10:45                                                                       ` Peter Zijlstra
2023-02-20 17:32                                                                         ` Boqun Feng
2023-02-13 18:46                                                             ` Kent Overstreet
2023-02-14 11:05                                                               ` Peter Zijlstra
2023-02-14 20:05                                                                 ` Alan Stern
2023-02-15 10:33                                                                   ` Peter Zijlstra
2023-02-14 20:16                                                                 ` Kent Overstreet
     [not found]                                               ` <20230212013220.2678-1-hdanton@sina.com>
2023-02-12  1:52                                                 ` Kent Overstreet
2023-02-13  9:49                                           ` Peter Zijlstra
2023-02-13 16:18                                             ` Alan Stern
2023-02-13 17:51                                               ` Greg Kroah-Hartman
2023-02-13 18:05                                                 ` Alan Stern
2023-02-05  1:31               ` Converting dev->mutex into dev->spinlock ? Tetsuo Handa
2023-02-05 16:46                 ` Alan Stern
2023-02-06  2:56                   ` Hillf Danton
2023-02-06  4:44                     ` Matthew Wilcox
2023-02-06  5:17                     ` Greg Kroah-Hartman
2023-02-06  6:43                       ` Hillf Danton
2023-02-06  6:48                         ` Greg Kroah-Hartman
2023-02-04 15:12 ` Alan Stern
2023-02-04 15:30   ` Tetsuo Handa
2023-02-04 15:40     ` Alan Stern
2023-02-05  0:21       ` Hillf Danton [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20230205002156.1071-1-hdanton@sina.com \
    --to=hdanton@sina.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=penguin-kernel@i-love.sakura.ne.jp \
    --cc=rafael@kernel.org \
    --cc=stern@rowland.harvard.edu \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.