linux-kernel - Re: Re: [PATCH bpf v2] bpf: Fix deadlock when freeing cgroup storage

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Message-ID: <CAADnVQLTTQNTAafm51o2fHSqdz+6uepEa=1VUiyQBN2sWQFm8Q@mail.gmail.com>
Date: Wed, 29 Jan 2025 18:40:29 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Abel Wu <wuyun.abel@...edance.com>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Eduard Zingerman <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>, David Vernet <void@...ifault.com>, 
	"open list:BPF [STORAGE & CGROUPS]" <bpf@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH bpf v2] bpf: Fix deadlock when freeing cgroup storage

On Tue, Jan 28, 2025 at 10:23 PM Abel Wu <wuyun.abel@...edance.com> wrote:
>
> On 1/28/25 7:05 AM, Martin KaFai Lau Wrote:
> > On 1/27/25 2:15 PM, Alexei Starovoitov wrote:
> >> On Sun, Jan 26, 2025 at 1:31 AM Abel Wu <wuyun.abel@...edance.com> wrote:
> >>>
> >>> On 1/25/25 4:20 AM, Martin KaFai Lau Wrote:
> >>>>
> >>>> imo, that should be a better option instead of having more unnecessary failures in all other normal use cases which will not be interested in tracing cgroup_storage_ptr().
> >>
> >> Martin,
> >>
> >> task_storage_map_free() is doing this busy inc/dec already,
> >> in that sense doing the same in cgroup_storage_map_free() fits.
> >
> > sgtm. Agree to be consistent with the task_storage_map_free.
> >
> > would be nice if the busy inc/dec usage can be revisited after the rqspinlock work.
>
> Agree, and 1ms interval of deadlock dection seems acceptable
> for most workloads.
>
> >
> > Acked-by: Martin KaFai Lau <martin.lau@...nel.org>
>
> Thanks Alexei, Martin.

Applied.