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Date:   Tue, 16 May 2023 22:29:19 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Beau Belgrave <beaub@linux.microsoft.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-trace-kernel@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
        David Vernet <void@manifault.com>, dthaler@microsoft.com,
        brauner@kernel.org, hch@infradead.org
Subject: Re: [PATCH] tracing/user_events: Run BPF program if attached
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On Tue, 16 May 2023 18:46:29 -0700
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> So don't even ask for other GUP functionality, much less the "remote"
> kind. Not going to happen. If you think you need access to remote
> process memory, you had better do it in process context, or you had
> better just think again.

So this code path is very much in user context (called directly by a
write system call). The issue that Alexei had was that it's also in an
rcu_read_lock() section.

I wonder if this all goes away if we switch to SRCU? That is, sleepable RCU.

-- Steve