linux-kernel - Re: [RFC PATCH 3/4] rculist.h: Fix parentheses around macro pointer parameter use

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Date:   Fri, 5 May 2023 10:35:39 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Zqiang <qiang1.zhang@...el.com>, rcu@...r.kernel.org
Subject: Re: [RFC PATCH 3/4] rculist.h: Fix parentheses around macro pointer parameter use



> On May 5, 2023, at 10:06 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> On Thu, 4 May 2023 12:19:38 -0400
> Joel Fernandes <joel@...lfernandes.org> wrote:
> 
>>>  void f(void)
>>>  {
>>>          struct test *t1;
>>>          struct test **t2 = &t1;
>>> 
>>>          list_for_each_entry_rcu((*t2), &testlist, node) {       /* works */
>>>                  //...
>>>          }
>>>          list_for_each_entry_rcu(*t2, &testlist, node) { /* broken */
>>>                  //...
>>>          }  
>> 
>> Yeah it is not clear why anyone would ever want to use it like this.
>> Why don't they just pass t1 to list_for_each_entry_rcu() ? I would
>> rather it break them and they re-think their code ;).
> 
> Remember interfaces should not be enforcing policy unless it's key to the
> way the interface works.

Oh yeah, 100% agree. I am not particularly against this particular patch but I also dont see it as solving any problem. Feel free to Ack the patch if you feel strongly about wanting it.

 - Joel


> 
> -- Steve