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From: Luis Chamberlain <mcgrof@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: ngupta@vflare.org, sergey.senozhatsky.work@gmail.com,
	axboe@kernel.dk, mbenes@suse.com, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] zram: fix crashes due to use of cpu hotplug multistate
Date: Wed, 10 Mar 2021 21:21:28 +0000	[thread overview]
Message-ID: <20210310212128.GR4332@42.do-not-panic.com> (raw)
In-Reply-To: <YEbjom8FIclEgRYv@google.com>

On Mon, Mar 08, 2021 at 06:55:30PM -0800, Minchan Kim wrote:
> If I understand correctly, bugs you found were related to module
> unloading race while the zram are still working.

No, that is a simplifcation of the issue. The issue consists of
two separate issues:

 a) race against module unloading in light of incorrect racty use of
    cpu hotplug multistate support
 b) module unload race with sysfs attribute race on *any* driver which
    has sysfs attributes which also shares the same lock as used during
    module unload

It is important to realize that issue b) is actually a generic kernel
issue, it would be present on *any* driver which shares a lock used on
a sysfs attribute and module unload. I looked to implement a generic
solution on kernfs, however we don't yet have semantics to enable this
generically, and so for now each driver needs to deal with those races
on their own. That sysfs race is dealt with in the second patch.

The first patch only deals with the cpu hotplug races exposed at module
unloading.

  Luis

  parent reply	other threads:[~2021-03-10 21:23 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-06  2:20 [PATCH 0/2] zram: fix few ltp zram02.sh crashes Luis Chamberlain
2021-03-06  2:20 ` [PATCH 1/2] zram: fix crashes due to use of cpu hotplug multistate Luis Chamberlain
2021-03-09  2:55   ` Minchan Kim
2021-03-10 13:11     ` Luis Chamberlain
2021-03-10 21:25       ` Luis Chamberlain
2021-03-12  2:08       ` Minchan Kim
2021-03-10 21:21     ` Luis Chamberlain [this message]
2021-03-12  2:14       ` Minchan Kim
2021-03-12 18:32         ` Luis Chamberlain
2021-03-12 19:28           ` Minchan Kim
2021-03-19 19:09             ` Luis Chamberlain
2021-03-22 16:37               ` Minchan Kim
2021-03-22 20:41                 ` Luis Chamberlain
2021-03-22 22:12                   ` Minchan Kim
2021-04-01 23:59                     ` Luis Chamberlain
2021-04-02  7:54                       ` Greg KH
2021-04-02 18:30                         ` Luis Chamberlain
2021-04-03  6:13                           ` Greg KH
     [not found]                             ` <20210406003152.GZ4332@42.do-not-panic.com>
2021-04-06 12:00                               ` Miroslav Benes
2021-04-06 15:54                                 ` Josh Poimboeuf
2021-04-07 14:09                                   ` Peter Zijlstra
2021-04-07 15:30                                     ` Josh Poimboeuf
2021-04-07 16:48                                       ` Peter Zijlstra
2021-04-07 20:17                         ` Josh Poimboeuf
2021-04-08  6:18                           ` Greg KH
2021-04-08 13:16                             ` Steven Rostedt
2021-04-08 13:37                             ` Josh Poimboeuf
2021-04-08  1:37                         ` Thomas Gleixner
2021-04-08  6:16                           ` Greg KH
2021-04-08  8:01                             ` Jiri Kosina
2021-04-08  8:09                               ` Greg KH
2021-04-08  8:35                                 ` Jiri Kosina
2021-04-08  8:55                                   ` Greg KH
2021-04-08 18:40                                     ` Luis Chamberlain
2021-04-09  3:01                                     ` Kees Cook
2021-04-05 17:07                       ` Minchan Kim
2021-04-05 19:00                         ` Luis Chamberlain
2021-04-05 19:58                           ` Minchan Kim
2021-04-06  0:29                             ` Luis Chamberlain
2021-04-07  1:23                               ` Minchan Kim
2021-04-07  1:38                                 ` Minchan Kim
2021-04-07 14:52                                   ` Luis Chamberlain
2021-04-07 14:50                                 ` Luis Chamberlain
2021-03-06  2:20 ` [PATCH 2/2] zram: fix races of sysfs attribute removal and usage Luis Chamberlain

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