linux-kernel - Re: backwards busy wait using "time

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Message-ID: <alpine.LFD.2.00.0912311421290.5803@localhost>
Date:	Thu, 31 Dec 2009 14:23:02 -0500 (EST)
From:	"Robert P. J. Day" <rpjday@...shcourse.ca>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: backwards busy wait using "time_before()"??

On Thu, 31 Dec 2009, Robert P. J. Day wrote:

>
>   if this is an idiotic question, i'll blame it on the fact that
> there's only decaf left in the house.
>
>   from drivers/spi/spi_stmp.c:
>
>    #define busy_wait(cond)                                              \
>         ({                                                              \
>         unsigned long end_jiffies = jiffies + STMP_SPI_TIMEOUT;         \
>         bool succeeded = false;                                         \
>         do {                                                            \
>                 if (cond) {                                             \
>                         succeeded = true;                               \
>                         break;                                          \
>                 }                                                       \
>                 cpu_relax();                                            \
>         } while (time_before(end_jiffies, jiffies));                    \
>         succeeded;                                                      \
>         })
>
>
>   is it just me, or do those arguments to time_before() look
> backwards?

  with a quick grep, i found one other example that looks reversed.
from drivers/char/hvsi.c:

static void hvsi_drain_input(struct hvsi_struct *hp)
{
        uint8_t buf[HVSI_MAX_READ] __ALIGNED__;
        unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;

        while (time_before(end_jiffies, jiffies))
                if (0 == hvsi_read(hp, buf, HVSI_MAX_READ))
                        break;
}


  surely that's backwards as well, no?

rday
--


========================================================================
Robert P. J. Day                               Waterloo, Ontario, CANADA

            Linux Consulting, Training and Kernel Pedantry.

Web page:                                          http://crashcourse.ca
Twitter:                                       http://twitter.com/rpjday
========================================================================
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