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References: <20240430-bpf-next-v3-0-27afe7f3b17c@kernel.org> <20240430-bpf-next-v3-2-27afe7f3b17c@kernel.org>
In-Reply-To: <20240430-bpf-next-v3-2-27afe7f3b17c@kernel.org>
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Tue, 30 Apr 2024 14:52:35 +0200
Message-ID: <CAP01T76NyoYc4Y6k_ArbjfUn1tVjxSa0SpqVzEtM0h9jdRvgDg@mail.gmail.com>
Subject: Re: [PATCH bpf-next v3 2/3] bpf: do not walk twice the hash map on free
To: Benjamin Tissoires <bentiss@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, 
	Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau <martin.lau@linux.dev>, 
	Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>, 
	Yonghong Song <yonghong.song@linux.dev>, John Fastabend <john.fastabend@gmail.com>, 
	KP Singh <kpsingh@kernel.org>, Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, 
	Jiri Olsa <jolsa@kernel.org>, Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>, 
	bpf@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-kselftest@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"

On Tue, 30 Apr 2024 at 12:44, Benjamin Tissoires <bentiss@kernel.org> wrote:
>
> If someone stores both a timer and a workqueue in a hash map, on free, we
> would walk it twice.
> Add a check in htab_free_malloced_timers_or_wq and free the timers
> and workqueues if they are present.
>
> Fixes: 246331e3f1ea ("bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps")
> Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
>
> ---

I had forgotten how the extra_elems logic is working, turns out
everything is in the preallocated elems array and per-cpu extra_elems
stores the *pointer* to them for recycling without hitting the pcpu
allocator, so should be fine (just in case this confuses anyone else).

>
> changes in v3:
> - fix unloading of bpf_wq, again
>
> changes in v2:
> - fix wq being not freed (and static call not used)
> ---

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>