From: Dennis Zhou <dennis@kernel.org>
To: Hou Tao <houtao@huaweicloud.com>
Cc: bpf@vger.kernel.org, linux-mm@kvack.org,
Martin KaFai Lau <martin.lau@linux.dev>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>, Song Liu <song@kernel.org>,
Hao Luo <haoluo@google.com>,
Yonghong Song <yonghong.song@linux.dev>,
Daniel Borkmann <daniel@iogearbox.net>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Jiri Olsa <jolsa@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
houtao1@huawei.com, Tejun Heo <tj@kernel.org>,
Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH bpf-next v2 1/7] mm/percpu.c: don't acquire pcpu_lock for pcpu_chunk_addr_search()
Date: Thu, 19 Oct 2023 20:55:11 -0700 [thread overview]
Message-ID: <ZTH6H7t7nouUXaEe@snowbird> (raw)
In-Reply-To: <20231018113343.2446300-2-houtao@huaweicloud.com>
On Wed, Oct 18, 2023 at 07:33:37PM +0800, Hou Tao wrote:
> From: Hou Tao <houtao1@huawei.com>
>
> There is no need to acquire pcpu_lock for pcpu_chunk_addr_search():
> 1) both pcpu_first_chunk & pcpu_reserved_chunk must have been
> initialized before the invocation of free_percpu().
> 2) The dynamically-created chunk must be valid before the per-cpu
> pointers allocated from it are freed.
>
> So acquire pcpu_lock() after the invocation of pcpu_chunk_addr_search().
>
> Signed-off-by: Hou Tao <houtao1@huawei.com>
> ---
> mm/percpu.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 7b40b3963f10..76b9c5e63c56 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -2267,12 +2267,10 @@ void free_percpu(void __percpu *ptr)
> kmemleak_free_percpu(ptr);
>
> addr = __pcpu_ptr_to_addr(ptr);
> -
> - spin_lock_irqsave(&pcpu_lock, flags);
> -
> chunk = pcpu_chunk_addr_search(addr);
> off = addr - chunk->base_addr;
>
> + spin_lock_irqsave(&pcpu_lock, flags);
> size = pcpu_free_area(chunk, off);
>
> pcpu_memcg_free_hook(chunk, off, size);
> --
> 2.29.2
>
Acked-by: Dennis Zhou <dennis@kernel.org>
Thanks,
Dennis
next prev parent reply other threads:[~2023-10-20 3:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-18 11:33 [PATCH bpf-next v2 0/7] bpf: Fixes for per-cpu kptr Hou Tao
2023-10-18 11:33 ` [PATCH bpf-next v2 1/7] mm/percpu.c: don't acquire pcpu_lock for pcpu_chunk_addr_search() Hou Tao
2023-10-20 3:55 ` Dennis Zhou [this message]
2023-10-18 11:33 ` [PATCH bpf-next v2 2/7] mm/percpu.c: introduce pcpu_alloc_size() Hou Tao
2023-10-20 2:18 ` Alexei Starovoitov
2023-10-20 4:09 ` Dennis Zhou
2023-10-20 4:16 ` Alexei Starovoitov
2023-10-20 7:09 ` Hou Tao
2023-10-18 11:33 ` [PATCH bpf-next v2 3/7] bpf: Re-enable unit_size checking for global per-cpu allocator Hou Tao
2023-10-18 11:33 ` [PATCH bpf-next v2 4/7] bpf: Use pcpu_alloc_size() in bpf_mem_free{_rcu}() Hou Tao
2023-10-18 11:33 ` [PATCH bpf-next v2 5/7] bpf: Move the declaration of __bpf_obj_drop_impl() to bpf.h Hou Tao
2023-10-18 11:33 ` [PATCH bpf-next v2 6/7] bpf: Use bpf_global_percpu_ma for per-cpu kptr in __bpf_obj_drop_impl() Hou Tao
2023-10-18 11:33 ` [PATCH bpf-next v2 7/7] selftests/bpf: Add more test cases for bpf memory allocator Hou Tao
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