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Subjectsomething about jiffies wraparound overflow
 Hello,

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)

#define time_after_eq(a,b) \
(typecheck(unsigned long, a) && \
typecheck(unsigned long, b) && \
((long)(a) - (long)(b) >= 0))
#define time_before_eq(a,b) time_after_eq(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)
{
/* not timeout...*/
}
else
{
/* timeout processing...*/
}

questions:
1.why the macros of time_after can solve the jiffies wraparound problem?
2.Is there any other possibilities for the "code 2" to overflow
except the jiffies overflow?

Any help will be preferred .
Thank you,


Yours.
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