linux-kernel - Re: [PATCH] mm/percpu.c: use smarter memory allocation for struct pcpu_alloc

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Message-ID: <20171003234801.GA1571@Big-Sky.local>
Date:   Tue, 3 Oct 2017 18:48:28 -0500
From:   Dennis Zhou <dennisszhou@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Nicolas Pitre <nicolas.pitre@...aro.org>,
        Christoph Lameter <cl@...ux.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/percpu.c: use smarter memory allocation for struct
 pcpu_alloc_info

Hi Tejun,

On Tue, Oct 03, 2017 at 03:36:42PM -0700, Tejun Heo wrote:
> > Subject: [PATCH] percpu: don't forget to free the temporary struct pcpu_alloc_info
> 
> So, IIRC, the error path is either boot fail or some serious bug in
> arch code.  It really doesn't matter whether we free a page or not.
>

In setup_per_cpu_area, a call to either pcpu_embed_first_chunk,
pcpu_page_first_chunk, or pcpu_setup_first_chunk is made. The first two
eventually call pcpu_setup_first_chunk with a pairing call to
pcpu_free_alloc_info right after. This occurs in all implementations. It
happens we don't have a pairing call to pcpu_free_alloc_info in the UP
setup_per_cpu_area.

Thanks,
Dennis