Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 19 Oct 2021 08:23:51 +0200 (CEST)
From:   Miroslav Benes <mbenes@suse.cz>
To:     Ming Lei <ming.lei@redhat.com>
cc:     Luis Chamberlain <mcgrof@kernel.org>,
        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
Subject: Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate
In-Reply-To: <YW4uwep3BCe9Vxq8@T590>
Message-ID: <alpine.LSU.2.21.2110190820590.15009@pobox.suse.cz>
References: <20210927163805.808907-12-mcgrof@kernel.org> <YWeOJP2UJWYF94fu@T590> <YWeR4moCRh+ZHOmH@T590> <YWiSAN6xfYcUDJCb@bombadil.infradead.org> <YWjCpLUNPF3s4P2U@T590> <YWjJ0O7K+31Iz3ox@bombadil.infradead.org> <YWk9e957Hb+I7HvR@T590>
 <YWm68xUnAofop3PZ@bombadil.infradead.org> <YWq3Z++uoJ/kcp+3@T590> <YW3LuzaPhW96jSBK@bombadil.infradead.org> <YW4uwep3BCe9Vxq8@T590>
User-Agent: Alpine 2.21 (LSU 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

> > By you only addressing the deadlock as a requirement on approach a) you are
> > forgetting that there *may* already be present drivers which *do* implement
> > such patterns in the kernel. I worked on addressing the deadlock because
> > I was informed livepatching *did* have that issue as well and so very
> > likely a generic solution to the deadlock could be beneficial to other
> > random drivers.
> 
> In-tree zram doesn't have such deadlock, if livepatching has such AA deadlock,
> just fixed it, and seems it has been fixed by 3ec24776bfd0.

I would not call it a fix. It is a kind of ugly workaround because the 
generic infrastructure lacked (lacks) the proper support in my opinion. 
Luis is trying to fix that.

Just my two cents.

Miroslav