linux-kernel - Re: [PATCH 1/2] ARC: show_regs: avoid page allocator

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Date:   Wed, 19 Dec 2018 17:36:35 +0000
From:   Vineet Gupta <vineet.gupta1@...opsys.com>
To:     Eugeniy Paltsev <eugeniy.paltsev@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] ARC: show_regs: avoid page allocator

On 12/19/18 9:04 AM, Eugeniy Paltsev wrote:
> Just curious: isn't that enough to use GFP_NOWAIT instead
> of GFP_KERNEL when we allocate page in show_regs()?
>
> As I can see x86 use print_vma_addr() in their show_signal_msg()
> function which allocate page with __get_free_page(GFP_NOWAIT);

I'm not sure if lockdep will be happy with it still.

At any rate, as explained in changelog, this still has merit, since the buffer is
only needed for nested d_path calls, which are better served with a smaller
on-stack buffer. For cases such as kernel crash, we want lesser code/traces in
fault path to sift thru !

-Vineet