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Date:   Mon, 1 Feb 2021 10:22:27 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>, andrii@kernel.org,
        Martin KaFai Lau <kafai@fb.com>,
        David Miller <davem@davemloft.net>, kpsingh@kernel.org,
        John Fastabend <john.fastabend@gmail.com>,
        netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: extended bpf_send_signal_thread with argument
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On Sun, Jan 31, 2021 at 12:14:02PM +0100, Dmitry Vyukov wrote:
> Hi,
> 
> I would like to send a signal from a bpf program invoked from a
> perf_event. There is:

You can't. Sending signals requires sighand lock, and you're not allowed
to take locks from perf_event context.