[QUESTION] init/main.c

[QUESTION] init/main.c

[Thiago Rondon]

At function calibrate_delay(void) in init/main.c,
I dont understand this code:

<<EOF
                /* wait for "start of" clock tick */
                ticks = jiffies;
                while (ticks == jiffies)
                        /* nothing */;
                /* Go .. */

                ticks = jiffies; 
EOF

ticks = jiffies; while (ticks == jiffies); ticks = jiffies; ?

Thanks in advanced,
-Thiago Rondon

Re: [QUESTION] init/main.c

[Bart Trojanowski]

jiffies is updated by a timer interrupt once every 1/HZ seconds (HZ==100
for i386).

The code intents to start running at the time right after jiffies was
incremented to improve the correctness of the delay calibration loop.

The reason why jiffies is read later is to get the value after the
change... if the interrupts are sporadic then the increment could be 2 ...
although not very likely.

Bart.

On Fri, 13 Apr 2001, Thiago Rondon wrote:

>
> At function calibrate_delay(void) in init/main.c,
> I dont understand this code:
>
> <<EOF
>                 /* wait for "start of" clock tick */
>                 ticks = jiffies;
>                 while (ticks == jiffies)
>                         /* nothing */;
>                 /* Go .. */
>
>                 ticks = jiffies;
> EOF
>
> ticks = jiffies; while (ticks == jiffies); ticks = jiffies; ?
>
> Thanks in advanced,
> -Thiago Rondon
>
> -
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Re: [QUESTION] init/main.c

[Jonathan Morton]

>ticks = jiffies; while (ticks == jiffies); ticks = jiffies; ?

jiffies is updated by an interrupt routine, I think.

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