Date:   Thu, 2 Feb 2023 15:38:58 +0100 (CET)
From:   Christoph Lameter <cl@gentwo.de>
To:     Marcelo Tosatti <mtosatti@redhat.com>
cc:     Aaron Tomlin <atomlin@atomlin.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold
In-Reply-To: <20230201195104.460373427@redhat.com>
Message-ID: <fb371ac-cf69-28a6-eca0-6caccda4e0b8@gentwo.de>
References: <20230201195013.881721887@redhat.com> <20230201195104.460373427@redhat.com>
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On Wed, 1 Feb 2023, Marcelo Tosatti wrote:

> In preparation to switch vmstat shepherd to flush
> per-CPU counters remotely, use a cmpxchg loop
> instead of a pair of read/write instructions.

You are mixing full atomic cmpxchg and  per cpu atomic cmpxchg? That does
not work.

I thought you would only run this while the kernel is not active on the
remote cpu? Then you dont need any cmpxchg and you can leave the function
as is.