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Jiffies not zero at boot

After a reboot, jiffies are not initialized to zero, but instead to some high value (near the wrapper).

For example (immediately after reboot):

cat /proc/timer_list | grep jiffies
    .idle_jiffies   : 4294902561
    .last_jiffies   : 4294902561
    .next_jiffies   : 4294902623
jiffies: 4294902561
    .idle_jiffies   : 4294902561
    .last_jiffies   : 4294902561
    .next_jiffies   : 4294902568
jiffies: 4294902561
    .idle_jiffies   : 4294902561
    .last_jiffies   : 4294902561
    .next_jiffies   : 4294902679
jiffies: 4294902561
    .idle_jiffies   : 4294902561
    .last_jiffies   : 4294902561
    .next_jiffies   : 4294902607

What am I missing? I am running Ubuntu 12.04 LTS, 3.13.0-36-generic. Thank!

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1 answer

When loading, jiffies are not initialized to zero, it is initialized by the constant INITIAL_JIFFIES.

You can see this constant in the Linux kernel headers:

$ cd your_path_to_linux_kernel_headers
$ grep INITIAL_JIFFIES linux/jiffies.h
#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))

This patch introduced this to identify problems associated with this overflow.

Sorry for waiting for an answer. :)

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