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Date:   Tue, 19 Oct 2021 12:38:42 -0700
From:   Luis Chamberlain <mcgrof@kernel.org>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     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,
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        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate
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Sender: Luis Chamberlain <mcgrof@infradead.org>
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On Wed, Oct 20, 2021 at 12:39:22AM +0800, Ming Lei wrote:
> On Tue, Oct 19, 2021 at 08:50:24AM -0700, Luis Chamberlain wrote:
> > So do you want to take the position:
> > 
> > Hey driver authors: you cannot use any shared lock on module removal and
> > on sysfs ops?
> 
> IMO, yes, in your patch of 'zram: fix crashes with cpu hotplug multistate',
> when you added mutex_lock(zram_index_mutex) to disksize_store() and
> other attribute show() or store() method. You have added new deadlock
> between hot_remove_store() and disksize_store() & others, which can't be
> addressed by your approach of holding module refcnt.
> 
> So far not see ltp tests covers hot add/remove interface yet.

Care to show what commands to use to cause this deadlock with my patches?

  Luis