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From: Clemens Ladisch <clemens@ladisch.de>
To: Corentin Labbe <clabbe.montjoie@gmail.com>, arnd@arndb.de
Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 5/6] hpet: removing unused variable m in hpet_interrupt
Date: Mon, 3 Apr 2017 14:55:14 +0200	[thread overview]
Message-ID: <64bd824c-2d09-3c8c-d35d-06d3808713b2@ladisch.de> (raw)
In-Reply-To: <20170403121559.1397-6-clabbe.montjoie@gmail.com>

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

  reply	other threads:[~2017-04-03 13:05 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-03 12:15 [PATCH v2 0/6] hpet: fix build warnings and style Corentin Labbe
2017-04-03 12:15 ` [PATCH v2 1/6] hpet: remove unused variable hpet in hpet_ioctl_common Corentin Labbe
2017-04-03 12:15 ` [PATCH v2 2/6] hpet: remove unused writeq/readq function definitions Corentin Labbe
2017-04-03 12:15 ` [PATCH v2 3/6] hpet: fix checkpatch complains about spaces Corentin Labbe
2017-04-03 12:15 ` [PATCH v2 4/6] hpet: replace printk by their pr_xxx counterparts Corentin Labbe
2017-04-03 19:44   ` Joe Perches
2017-04-03 12:15 ` [PATCH v2 5/6] hpet: removing unused variable m in hpet_interrupt Corentin Labbe
2017-04-03 12:55   ` Clemens Ladisch [this message]
2017-04-03 12:15 ` [PATCH v2 6/6] hpet: fix style issue about braces and alignment Corentin Labbe
2017-04-04  3:43   ` Joe Perches
  -- strict thread matches above, loose matches on Subject: below --
2017-03-30  2:53 [PATCH 0/2] Support new Alps HID I2C Touchpad device Masaki Ota
2017-03-30  2:53 ` [PATCH 1/2] Alps HID I2C T4 device support Masaki Ota
2017-04-04  3:08   ` Nikolaus Rath
2017-04-04  6:55     ` Masaki Ota
2017-04-04 17:08       ` Nikolaus Rath
2017-04-04 17:08         ` Nikolaus Rath
2017-04-04 23:40         ` Masaki Ota
2017-04-04 23:42           ` Nikolaus Rath
2017-04-04 23:42             ` Nikolaus Rath
2017-04-04 23:49             ` Masaki Ota
2017-04-05  0:01               ` Nikolaus Rath
2017-04-05  0:01                 ` Nikolaus Rath
2017-04-05  8:43                 ` Masaki Ota
2017-04-05 18:35                   ` Nikolaus Rath
2017-04-05 18:35                     ` Nikolaus Rath
2017-04-06  1:07                     ` Masaki Ota
2017-04-06 22:59                       ` Nikolaus Rath
2017-04-06 22:59                         ` Nikolaus Rath
2017-04-24 14:54   ` Benjamin Tissoires
2017-03-30  2:53 ` [PATCH 2/2] Add new U1 device ID Masaki Ota

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