jeff shia <[email protected]> wrote:
> we use the following to solve the problem of jiffies wraparound.
> #define time_after(a,b) \
> (typecheck(unsigned long, a) && \
> typecheck(unsigned long, b) && \
> ((long)(b) - (long)(a) < 0))
> #define time_before(a,b) time_after(b,a)
[...]
> But I cannot understand it has some differences comparing with the
> following code.
>
> /* code 2*/
>
> unsigned long timeout = jiffies + HZ/2;
>
> if(timeout < jiffies)
> questions:
> 1.why the macros of time_after can solve the jiffies wraparound problem?
Because the overflows get compensated. It's a property of Galois Fields.
> 2.Is there any other possibilities for the "code 2" to overflow
> except the jiffies overflow?
timeout might overflow, too.
--
Ich danke GMX dafür, die Verwendung meiner Adressen mittels per SPF
verbreiteten Lügen zu sabotieren.
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