Need your help on setting of INITIAL_JIFFIES

Need your help on setting of INITIAL_JIFFIES

[MOHANTY CHANDAN-WJKD64]

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Hi,
My greetings to all the enlightened Linux Souls.
 
 I got all the mail ids from one of Linux based mail chain/URL
http://www.linux-mips.org/archives/linux-mips/2006-05/msg00193.html
 
Pls guide me on the usage of  INITIAL_JIFFIES.
 
 
 
 
In the source of linux kernel \include\linux\jiffies.h there is code
like this
 
/*
 * Have the 32 bit jiffies value wrap 5 minutes after boot
 * so jiffies wrap bugs show up earlier.
 */
#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
 
 
 This sets the initial jiffies value to 0x00000000fffb6c20, which can
trigger 32-bit wraparound bugs .It is an offset to the jiffies
counter,so that it begins from a large value instead of zero. So the
wrap-around happens earlier,making it possible to detect any counter
wrap-around bugs much quicker regardless of the HZ setting.
 
 
 
 
1.Suppose I want to simulate the jiffies wraparound after 30
mins(1800sec) of reboot.Can I change code as below in kernel?
 
#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-1800*HZ))
u64 jiffies_64 = INITIAL_JIFFIES;
 
 
2.How to verify/test that wraparound has happened?
 
 
Regards
Chandan

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Need your help on setting of INITIAL_JIFFIES

[MOHANTY CHANDAN-WJKD64]

[-- Attachment #1: Type: text/plain, Size: 1183 bytes --]

Hi,
My greetings to all the enlightened Linux Souls.
 
 I got all the mail ids from one of Linux based mail chain/URL
http://www.linux-mips.org/archives/linux-mips/2006-05/msg00193.html
 
Pls guide me on the usage of  INITIAL_JIFFIES.
 
 
 
 
In the source of linux kernel \include\linux\jiffies.h there is code
like this
 
/*
 * Have the 32 bit jiffies value wrap 5 minutes after boot
 * so jiffies wrap bugs show up earlier.
 */
#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
 
 
 This sets the initial jiffies value to 0x00000000fffb6c20, which can
trigger 32-bit wraparound bugs .It is an offset to the jiffies
counter,so that it begins from a large value instead of zero. So the
wrap-around happens earlier,making it possible to detect any counter
wrap-around bugs much quicker regardless of the HZ setting.
 
 
 
 
1.Suppose I want to simulate the jiffies wraparound after 30
mins(1800sec) of reboot.Can I change code as below in kernel?
 
#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-1800*HZ))
u64 jiffies_64 = INITIAL_JIFFIES;
 
 
2.How to verify/test that wraparound has happened?
 
 
Regards
Chandan

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