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:   Mon, 14 Sep 2020 12:59:42 -0700 (PDT)
Message-Id: <20200914.125942.5644261129883859.davem@davemloft.net>
To:     npiggin@gmail.com
Cc:     linux-mm@kvack.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        sparclinux@vger.kernel.org, aneesh.kumar@linux.ibm.com,
        akpm@linux-foundation.org, axboe@kernel.dk, peterz@infradead.org
Subject: Re: [PATCH v2 3/4] sparc64: remove mm_cpumask clearing to fix
 kthread_use_mm race
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20200914045219.3736466-4-npiggin@gmail.com>
References: <20200914045219.3736466-1-npiggin@gmail.com>
        <20200914045219.3736466-4-npiggin@gmail.com>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Nicholas Piggin <npiggin@gmail.com>
Date: Mon, 14 Sep 2020 14:52:18 +1000

 ...
> The basic fix for sparc64 is to remove its mm_cpumask clearing code. The
> optimisation could be effectively restored by sending IPIs to mm_cpumask
> members and having them remove themselves from mm_cpumask. This is more
> tricky so I leave it as an exercise for someone with a sparc64 SMP.
> powerpc has a (currently similarly broken) example.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Sad to see this optimization go away, but what can I do:

Acked-by: David S. Miller <davem@davemloft.net>