linux-kernel - Re: [PATCH] bpf: Convert lpm_trie::lock to 'raw_spinlock

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Message-ID: <CAADnVQ+ToRZ6ZQL44Z9TAn6c=ecqrDgrnJenH7-miHJSWe7Nsw@mail.gmail.com>
Date: Sat, 16 Nov 2024 08:01:49 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Thomas Gleixner <tglx@...utronix.de>, Kunwu Chan <kunwu.chan@...ux.dev>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eddy Z <eddyz87@...il.com>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	clrkwllms@...nel.org, Steven Rostedt <rostedt@...dmis.org>, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, linux-rt-devel@...ts.linux.dev, 
	syzbot+b506de56cbbb63148c33@...kaller.appspotmail.com, 
	Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: Re: [PATCH] bpf: Convert lpm_trie::lock to 'raw_spinlock_t'

On Sat, Nov 16, 2024 at 1:21 AM Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>
> On 2024-11-15 23:29:31 [+0100], Thomas Gleixner wrote:
> > IIRC, BPF has it's own allocator which can be used everywhere.
>
> Thomas Weißschuh made something. It appears to work. Need to take a
> closer look.

Any more details?
bpf_mem_alloc is a stop gap.
As Vlastimil Babka suggested long ago:
https://lwn.net/Articles/974138/
"...next on the target list is the special allocator used by the BPF
subsystem. This allocator is intended to succeed in any calling
context, including in non-maskable interrupts (NMIs). BPF maintainer
Alexei Starovoitov is evidently in favor of this removal if SLUB is
able to handle the same use cases..."

Here is the first step:
https://lore.kernel.org/bpf/20241116014854.55141-1-alexei.starovoitov@gmail.com/