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Date:   Thu, 10 Mar 2022 09:27:42 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Changbin Du <changbin.du@gmail.com>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Ingo Molnar <mingo@redhat.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: ftrace: no need to acquire text_mutex when
 executed in stop_machine
Message-ID: <20220310092742.4fcc7131@gandalf.local.home>
In-Reply-To: <20220310045454.672097-1-changbin.du@gmail.com>
References: <20220310045454.672097-1-changbin.du@gmail.com>
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On Thu, 10 Mar 2022 12:54:54 +0800
Changbin Du <changbin.du@gmail.com> wrote:

> It's safe to patch text segment in stop_machine. No race is possible here.
> Besides, there is a false positive for the lock assertion in
> patch_insn_write() since the lock is not held by cpu migration thread.
> 
> So we actually don't need our ftrace_arch_code_modify_prepare/post(). And
> the lock assertion in patch_insn_write() should be removed to avoid
> producing lots of false positive warnings.
> 
> Signed-off-by: Changbin Du <changbin.du@gmail.com>

Ideally, RISC-V should try to get off of the stop_machine approach, and
move to the breakpoint modification.

-- Steve