Subject: Re: [PATCH v2 5/6] hpet: removing unused variable m in hpet_interrupt
To: Corentin Labbe <clabbe.montjoie@gmail.com>, arnd@arndb.de
References: <20170403121559.1397-1-clabbe.montjoie@gmail.com>
 <20170403121559.1397-6-clabbe.montjoie@gmail.com>
Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org
From: Clemens Ladisch <clemens@ladisch.de>
Message-ID: <64bd824c-2d09-3c8c-d35d-06d3808713b2@ladisch.de>
Date: Mon, 3 Apr 2017 14:55:14 +0200
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Corentin Labbe wrote:
> This patch fix the following warning:
> drivers/char/hpet.c:146:17: attention : variable ‘m’ set but not used [-Wunused-but-set-variable]
> by removing the unused variable m in hpet_interrupt

This patch might silence the warning, but it leaves the bug that
actually caused the warning.

As far as I can see, the computation of "base" should use "m".

But the entire algorithm is completely bogus because it does not
actually remove the race condition; the counter is likely to have
advanced beyond the "mc" value when the new comparator value is
written.  Also see arch/x86/kernel/hpet.c for how hpet_next_event()
handles this.

And why a non-periodic timer should generate periodic interrupts is
another question.

And nobody uses this crap.
So I'm really not sure what to do about this ...


Regards,
Clemens