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SubjectRe: patch: delay_50ms() in ide-probe.c in 2.2.14
Date
arijort@valinux.com writes:
> Simple arithmetic tells me this patch
>
> a) produces same behavior as previous code, and
> b) does it with fewer calculations.
>
> So it has to be good, right?
> But then how do we exit the while loop?
> How does jiffies change?
>
> This patch applies cleanly against 2.2.14
> Against 2.3.45, the relevant file is ide.c
> but otherwise, it's clean.

It's also wrong. (HZ + 39)/20 is constant, and you therefore have
effectively a while(1); loop there now.
(Hint: 'jiffies' is updated in an interrupt routine which is enabled
throughout this function).

> --- drivers/block/ide-probe.c.orig Sun Feb 20 00:46:54 2000
> +++ drivers/block/ide-probe.c Sun Feb 20 07:28:32 2000
> @@ -154,8 +154,7 @@
> */
> static void delay_50ms (void)
> {
> - unsigned long timeout = jiffies + ((HZ + 19)/20) + 1;
> - while (0 < (signed long)(timeout - jiffies));
> + while (0 < (signed long)((HZ + 39)/20));
> }
>
> /*
_____
|_____| ------------------------------------------------- ---+---+-
| | Russell King rmk@arm.linux.org.uk --- ---
| | | | http://www.arm.linux.org.uk/~rmk/aboutme.html / / |
| +-+-+ --- -+-
/ | THE developer of ARM Linux |+| /|\
/ | | | --- |
+-+-+ ------------------------------------------------- /\\\ |

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