linux-kernel - RE: [PATCH bpf-next] bpf, sockmap: fix deadlocks in the sockhash and sockmap

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Date:   Thu, 06 Apr 2023 14:13:23 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Xin Liu <liuxin350@...wei.com>, andrii@...nel.org, ast@...nel.org,
        daniel@...earbox.net, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
        sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org
Cc:     bpf@...r.kernel.org, hsinweih@....edu,
        linux-kernel@...r.kernel.org, yanan@...wei.com,
        wuchangye@...wei.com, xiesongyang@...wei.com,
        kongweibin2@...wei.com, liuxin350@...wei.com,
        zhangmingyi5@...wei.com
Subject: RE: [PATCH bpf-next] bpf, sockmap: fix deadlocks in the sockhash and
 sockmap

Xin Liu wrote:
> When huang uses sched_switch tracepoint, the tracepoint
> does only one thing in the mounted ebpf program, which
> deletes the fixed elements in sockhash ([0])
> 
> It seems that elements in sockhash are rarely actively
> deleted by users or ebpf program. Therefore, we do not
> pay much attention to their deletion. Compared with hash
> maps, sockhash only provides spin_lock_bh protection.
> This causes it to appear to have self-locking behavior
> in the interrupt context.
> 
>   [0]:https://lore.kernel.org/all/CABcoxUayum5oOqFMMqAeWuS8+EzojquSOSyDA3J_2omY=2EeAg@mail.gmail.com/
> 
> Reported-by: Hsin-Wei Hung <hsinweih@....edu>
> Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
> Signed-off-by: Xin Liu <liuxin350@...wei.com>

Yeah even if we delete entries we do it from a sockops. Thanks for the
fix.

Acked-by: John Fastabend <john.fastabend@...il.com>