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From: Luis Chamberlain <mcgrof@kernel.org>
To: Ming Lei <ming.lei@redhat.com>, Julia Lawall <julia.lawall@inria.fr>
Cc: Petr Mladek <pmladek@suse.com>, Miroslav Benes <mbenes@suse.cz>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	tj@kernel.org, gregkh@linuxfoundation.org,
	akpm@linux-foundation.org, minchan@kernel.org, jeyu@kernel.org,
	shuah@kernel.org, bvanassche@acm.org, dan.j.williams@intel.com,
	joe@perches.com, tglx@linutronix.de, keescook@chromium.org,
	rostedt@goodmis.org, linux-spdx@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-kernel@vger.kernel.org, live-patching@vger.kernel.org
Subject: Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate
Date: Tue, 26 Oct 2021 10:01:40 -0700	[thread overview]
Message-ID: <YXg0dFZ+6qHw7d0g@bombadil.infradead.org> (raw)
In-Reply-To: <YXgguuAY5iEUIV0u@T590>

On Tue, Oct 26, 2021 at 11:37:30PM +0800, Ming Lei wrote:
> On Tue, Oct 26, 2021 at 10:48:18AM +0200, Petr Mladek wrote:
> > Livepatch code never called kobject_del() under a lock. It would cause
> > the obvious deadlock.

Never?

> > The historic code only waited in the
> > module_exit() callback until the sysfs interface was removed.
> 
> OK, then Luis shouldn't consider livepatching as one such issue to solve
> with one generic solution.

It's not what I was told when the deadlock was found with zram, so I was
informed quite the contrary.

I'm working on a generic coccinelle patch which hunts for actual cases
using iteration (a feature of coccinelle for complex searches). The
search is pretty involved, so I don't think I'll have an answer to this
soon.

Since the question of how generic this deadlock is remains questionable,
I think it makes sense to put the generic deadlock fix off the table for
now, and we address this once we have a more concrete search with
coccinelle.

But to say we *don't* have drivers which can cause this is obviously
wrong as well, from a cursory search so far. But let's wait and see how
big this list actually is.

I'll drop the deadlock generic fixes and move on with at least a starter
kernfs / sysfs tests.

  Luis

  reply	other threads:[~2021-10-26 17:02 UTC|newest]

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-27 16:37 [PATCH v8 00/12] syfs: generic deadlock fix with module removal Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 01/12] LICENSES: Add the copyleft-next-0.3.1 license Luis Chamberlain
     [not found]   ` <202110050907.35FBD2A1@keescook>
     [not found]     ` <YWR2ZrtzChamY1y4@bombadil.infradead.org>
2021-10-11 17:57       ` Kees Cook
2021-09-27 16:37 ` [PATCH v8 02/12] testing: use the copyleft-next-0.3.1 SPDX tag Luis Chamberlain
2021-10-05 16:11   ` Kees Cook
2021-09-27 16:37 ` [PATCH v8 03/12] selftests: add tests_sysfs module Luis Chamberlain
2021-10-05 14:16   ` Greg KH
2021-10-05 16:57     ` Tim.Bird
2021-10-11 17:40       ` Luis Chamberlain
2021-10-11 17:38     ` Luis Chamberlain
2021-10-07 14:23   ` Miroslav Benes
2021-10-11 19:11     ` Luis Chamberlain
     [not found]   ` <202110050912.3DF681ED@keescook>
2021-10-11 19:03     ` Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 04/12] kernfs: add initial failure injection support Luis Chamberlain
2021-10-05 19:47   ` Kees Cook
2021-10-11 20:44     ` Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 05/12] test_sysfs: add support to use kernfs failure injection Luis Chamberlain
2021-10-05 19:51   ` Kees Cook
2021-10-11 20:56     ` Luis Chamberlain
2021-09-27 16:37 ` [PATCH v8 06/12] kernel/module: add documentation for try_module_get() Luis Chamberlain
2021-10-05 19:58   ` Kees Cook
2021-10-11 21:16     ` Luis Chamberlain
2021-09-27 16:38 ` [PATCH v8 07/12] fs/kernfs/symlink.c: replace S_IRWXUGO with 0777 on kernfs_create_link() Luis Chamberlain
2021-10-05 19:59   ` Kees Cook
2021-09-27 16:38 ` [PATCH v8 08/12] fs/sysfs/dir.c: replace S_IRWXU|S_IRUGO|S_IXUGO with 0755 sysfs_create_dir_ns() Luis Chamberlain
2021-10-05 16:05   ` Kees Cook
2021-09-27 16:38 ` [PATCH v8 09/12] sysfs: fix deadlock race with module removal Luis Chamberlain
2021-10-05  9:24   ` Ming Lei
2021-10-11 21:25     ` Luis Chamberlain
2021-10-12  0:20       ` Ming Lei
2021-10-12 21:18         ` Luis Chamberlain
2021-10-13  1:07           ` Ming Lei
2021-10-13 12:35             ` Luis Chamberlain
2021-10-13 15:04               ` Ming Lei
2021-10-13 21:16                 ` Luis Chamberlain
2021-10-05 20:50   ` Kees Cook
2021-10-11 22:26     ` Luis Chamberlain
2021-10-13 12:41       ` Luis Chamberlain
2021-09-27 16:38 ` [PATCH v8 10/12] test_sysfs: enable deadlock tests by default Luis Chamberlain
2021-09-27 16:38 ` [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate Luis Chamberlain
2021-10-05 20:55   ` Kees Cook
2021-10-11 18:27     ` Luis Chamberlain
2021-10-14  1:55   ` Ming Lei
2021-10-14  2:11     ` Ming Lei
2021-10-14 20:24       ` Luis Chamberlain
2021-10-14 23:52         ` Ming Lei
2021-10-15  0:22           ` Luis Chamberlain
2021-10-15  8:36             ` Ming Lei
2021-10-15  8:52               ` Greg KH
2021-10-15 17:31               ` Luis Chamberlain
2021-10-16 11:28                 ` Ming Lei
2021-10-18 19:32                   ` Luis Chamberlain
2021-10-19  2:34                     ` Ming Lei
2021-10-19  6:23                       ` Miroslav Benes
2021-10-19  9:23                         ` Ming Lei
2021-10-20  6:43                           ` Miroslav Benes
2021-10-20  7:49                             ` Ming Lei
2021-10-20  8:19                               ` Miroslav Benes
2021-10-20  8:28                                 ` Greg KH
2021-10-25  9:58                                   ` Miroslav Benes
2021-10-20 10:09                                 ` Ming Lei
2021-10-26  8:48                                   ` Petr Mladek
2021-10-26 15:37                                     ` Ming Lei
2021-10-26 17:01                                       ` Luis Chamberlain [this message]
2021-10-27 11:57                                         ` Miroslav Benes
2021-10-27 14:27                                           ` Luis Chamberlain
2021-11-02 15:24                                           ` Petr Mladek
2021-11-02 16:25                                             ` Luis Chamberlain
2021-11-03  0:01                                               ` Ming Lei
2021-11-03 12:44                                                 ` Luis Chamberlain
2021-10-27 11:42                                       ` Miroslav Benes
2021-11-02 14:15                                       ` Petr Mladek
2021-11-02 14:51                                         ` Petr Mladek
2021-11-02 15:17                                           ` Ming Lei
2021-11-02 14:56                                         ` Ming Lei
2021-10-19 15:28                       ` Luis Chamberlain
2021-10-19 16:29                         ` Ming Lei
2021-10-19 19:36                           ` Luis Chamberlain
2021-10-20  1:15                             ` Ming Lei
2021-10-20 15:48                               ` Luis Chamberlain
2021-10-21  0:39                                 ` Ming Lei
2021-10-21 17:18                                   ` Luis Chamberlain
2021-10-22  0:05                                     ` Ming Lei
2021-10-19 15:50                       ` Luis Chamberlain
2021-10-19 16:25                         ` Greg KH
2021-10-19 16:30                           ` Luis Chamberlain
2021-10-19 17:28                             ` Greg KH
2021-10-19 19:46                               ` Luis Chamberlain
2021-10-19 16:39                         ` Ming Lei
2021-10-19 19:38                           ` Luis Chamberlain
2021-10-20  0:55                             ` Ming Lei
2021-09-27 16:38 ` [PATCH v8 12/12] zram: use ATTRIBUTE_GROUPS to fix sysfs deadlock module removal Luis Chamberlain
2021-10-05 20:57   ` Kees Cook
2021-10-11 18:28     ` Luis Chamberlain

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