Can jiffies freeze?

[bill4carson@gmail.com (bill4carson)]

On 2013?01?23? 03:32, sandeep kumar wrote:
>
> Hi Mr.Valdis
> as you rightly mentioned,cat /proc/kmsg is showing the time stamps, according to that it is 0ms only.
> But when you see the same with UART there is 2sec delay in showing the next log. i caught this while i m observing the UART logs with "Terminaliranicca".
>
Hmmm, all the boot messages are routed into a buffer it first printed into console, here there is no delay, possible tick timer are not setup yet.
But when it does get printed into the console, this process could be interrupted by other action as well, that's where you see a 2sec delay.

I hope I make myself clear:)





> Since i m early in the mm_init, i cant use watchdog to detect it, hrtimers i cant use..i am really thinking how to analyse this delay..
>
> Thanks
> Sandeep
>
> On Tue, Jan 22, 2013 at 10:40 AM, <Valdis.Kletnieks at vt.edu <mailto:Valdis.Kletnieks@vt.edu>> wrote:
>
>     On Tue, 22 Jan 2013 10:29:05 -0800, sandeep kumar said:
>
>      > I am seeing this problem at the very early in the start_kernel-->
>      > mm_init--> free_highpages, at that time nothing is up and kernel is running
>      > in single thread.
>
>     If you build a kernel with printk timestamps, you'll see that they all
>     come out like this:
>
>     [    0.000000] Initializing cgroup subsys cpuset
>     [    0.000000] Initializing cgroup subsys cpu
>     [    0.000000] Linux version 3.8.0-rc3-next-20130117-dirty (valdis at turing-police.cc.vt.edu <mailto:valdis@turing-police.cc.vt.edu>) (gcc version 4.7.2 20121109 (Red Hat 4.7.2-9) (GCC) ) #49 SMP PREEMPT Thu Jan 17 13:25:28 EST 2013
>     [    0.000000] Command line: ro root=/dev/mapper/vg_blackice-root log_buf_len=2M vga=893 loglevel=4 threadirqs intel_iommu=off LANG=en_US.UTF-8
>     [    0.000000] KERNEL supported cpus:
>     [    0.000000]   Intel GenuineIntel
>     [    0.000000] e820: BIOS-provided physical RAM map:
>     [    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009bbff] usable
>     [    0.000000] BIOS-e820: [mem 0x000000000009bc00-0x000000000009ffff] reserved
>     (100 or so more lines with same timestamp)
>     (now we finish memory init)
>     [    0.000000] Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes)
>     [    0.000000] Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
>     [    0.000000] __ex_table already sorted, skipping sort
>     [    0.000000] xsave: enabled xstate_bv 0x3, cntxt size 0x240
>     [    0.000000] Memory: 4015936k/4718592k available (6266k kernel code, 536744k absent, 165912k reserved, 7260k data, 576k init)
>     (more lines skipped)
>     [    0.000000]  memory used by lock dependency info: 5855 kB
>     [    0.000000]  per task-struct memory footprint: 1920 bytes
>     [    0.000000] hpet clockevent registered
>     [    0.000000] tsc: Fast TSC calibration using PIT
>     [    0.000000] tsc: Detected 2527.012 MHz processor
>     [    0.001004] Calibrating delay loop (skipped), value calculated using timer frequency.. 5054.02 BogoMIPS (lpj=2527012)
>     [    0.001009] pid_max: default: 32768 minimum: 301
>     [    0.001100] Security Framework initialized
>
>     It probably simply be that your code is running before the clock is started
>     by the kernel.
>
>
>
>
> --
> With regards,
> Sandeep Kumar Anantapalli,
>
>
>
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-- 
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--bill