Re: [patch 3/6] futex: Get rid of the val2 conditional dance

From: Thomas Gleixner <tglx@linutronix.de>
To: "André Almeida" <andrealmeid@collabora.com>,
	LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Adhemerval Zanella <adhemerval.zanella@linaro.org>,
	Lukasz Majewski <lukma@denx.de>,
	Florian Weimer <fweimer@redhat.com>,
	Carlos O'Donell <carlos@redhat.com>,
	"Michael Kerrisk \(man-pages\)" <mtk.manpages@gmail.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Ingo Molnar <mingo@kernel.org>,
	Darren Hart <dvhart@infradead.org>,
	Andrei Vagin <avagin@gmail.com>,
	Kurt Kanzenbach <kurt@linutronix.de>,
	kernel@collabora.com
Subject: Re: [patch 3/6] futex: Get rid of the val2 conditional dance
Date: Sat, 24 Apr 2021 00:34:00 +0200	[thread overview]
Message-ID: <87r1j0vdev.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <f8cda7fa-46e9-5add-ccb6-441323ba2042@collabora.com>

On Fri, Apr 23 2021 at 18:40, André Almeida wrote:
>>   
>> -	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
>> +	return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
>
> Given do_futex()'s type signature, I think it makes more sense to cast 
> utime to u32.

It's a pointer which you better force cast to unsigned long first.

So the explicit thing would be '(u32)(unsigned long) utime' which is
what the val2 dance stupidly did with 'int'

		val2 = (int) (unsigned long) utime;

But with doing it at function call argument it's implicit, because the

  unsigned long  to u32 conversion is well defined

while

  (u32)ptr

is only well defined on 32bit.

Thanks,

        tglx