Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:8 as permitted sender) client-ip=2620:137:e000::3:8;
Date:   Tue, 19 Sep 2023 21:35:16 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Bartosz Golaszewski <bartosz.golaszewski@linaro.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        linux-kernel@vger.kernel.org,
        Linus Walleij <linus.walleij@linaro.org>,
        akpm@linux-foundation.org
Subject: Re: Buggy __free(kfree) usage pattern already in tree
Message-ID: <20230919193516.GA20937@noisy.programming.kicks-ass.net>
References: <CACMJSevrJ5KSPAZVheXkNaYj8KQFD8ck55kU_E4vEj4vzR8wnQ@mail.gmail.com>
 <CAHk-=wicfvWPuRVDG5R1mZSxD8Xg=-0nLOiHay2T_UJ0yDX42g@mail.gmail.com>
 <20230915210851.GA23174@noisy.programming.kicks-ass.net>
 <CAHk-=whvOGL3aNhtps0YksGtzvaob_bvZpbaTcVEqGwNMxB6xg@mail.gmail.com>
 <20230915213231.GB23174@noisy.programming.kicks-ass.net>
 <CAHk-=wi08ZUguV_n88h=bP6X01-tah29RtB0t9TmXtyuEJev-Q@mail.gmail.com>
 <20230915221332.GC23174@noisy.programming.kicks-ass.net>
 <20230919125752.GA39346@noisy.programming.kicks-ass.net>
 <20230919125954.GB39346@noisy.programming.kicks-ass.net>
 <20230919131038.GC39346@noisy.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230919131038.GC39346@noisy.programming.kicks-ass.net>
Precedence: bulk

On Tue, Sep 19, 2023 at 03:10:38PM +0200, Peter Zijlstra wrote:

> This isn't exactly nice..
> 
> I tried something like:
> 
> 	scoped_cond_guard (mutex_intr, return -EINTR, &task->signal->cred_guard_mutex) {
> 		...
> 	}
> 
> Which I can make work, but then I also tried to capture my other case:
> 
> 	scoped_cond_guard (rwsem_down_intr, if (task) return -EINTR,
> 			   task ? &task->signal->exec_guard_mutex : NULL)  {
> 
> 		...
> 	}
> 
> But I can't get that to work because of that extra if, the not case
> doesn't fall through and do the body.
> 
> Anyway, I'll poke more..


#define scoped_cond_guard(_name, _label, args...)		\
	for (CLASS(_name, scope)(args),				\
	     *done = NULL; !done; done = (void *)1)		\
		if (!__guard_ptr(_name)(&scope)) goto _label;	\
		else

Allows one to write:

	scoped_cond_guard (rwsem_down_intr, no_lock,
 			   task ? &task->signal->exec_guard_mutex : NULL)  {

		if (0) {
no_lock:
			if (task)
				return -EINTR;
		}

		... block that holds exec_guard_mutex if task ...
	}

Still not exactly pretty, but perhaps better than before...