75 lines
2.9 KiB
Plaintext
75 lines
2.9 KiB
Plaintext
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Bug Id: 4095849
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Category: kernel
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Subcategory: syscall
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State: evaluated
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Synopsis: time_constant value >6 with PLL in use leads to integer divide
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zero trap panic
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Description:
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If the time_constant parameter is 7 or higher, and the phase-lock looping model
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is in use, the system will take a "integer divide zero trap" panic in
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the clock routine as soon as the time_offset becomes non-zero.
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time_constant defaults to 0. The only place it is set is in the ntp_adjtime
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system call, from the 'constant' element of the timex structure argument.
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Work around:
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Never set the constant element of the timex structure passed to ntp_adjtime to
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a value larger than 6.
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satish.mynam@Eng 1998-04-30
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1. Use Sun's version of NTP software instead of PD version. This problem
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is not seen with Sun's NTP version (which is mostly eqivalent to PD NTP 3.4
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plus some Sun's local functionality futures).
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2. Workaround for the public domain NTP version ONLY:
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=====================================================
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The workaround for public domain NTP version is to disable the
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KERNEL_PLL from the NTP code. This way ntp_Adjtime() system call is
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totally bypassed without sacrificing any of the functionality of the
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NTP. The only hit you might see is the way kernel precision timminig
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is done without the PLL algorithm in the kernel.
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The easiest way to disable ntp_adjtime option is(without changing
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any makefiles or other config files) to disable the KERNEL_PLL
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value in the ./config.h file.
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After doing a ./configure for probing for all the necessary tools(compilers,
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os version, libraries), please comment out KERNEL_PLL macro in
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the ./config.h file. This will disable the KERNEL_PLL part of the source
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code and the newly obtained xntpd is just similar to the old one but it
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does not use ntp_adjtime() system call. This prevents it from panic'ng
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the kernel.
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/*#define KERNEL_PLL 1*/
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I complied a new xntpd binary this way and it does nothave any ntp_adjtime()
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related stuff.
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Default:
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=======
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/net/divya/export/home/mynam/public_domain/ntp/xntp3-5.92/xntpd>strings
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xntpd |
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grep ntp_adjtime
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354:adj_frequency: ntp_adjtime failed: %m
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357:loop_config: ntp_adjtime() failed: %m
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435:get_kernel_info: ntp_adjtime() failed: %m
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With KERNEL_PLL disabled in config.h file
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-=======================
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/net/divya/export/home/mynam/public_domain/ntp/xntp3-5.92/xntpd>strings
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xntpd.nopll | grep ntp_adjtime
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Integrated in releases:
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Duplicate of:
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Patch id:
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See also: 4133517
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Summary:
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If the time_constant parameter is 7 or higher, and the phase-lock looping model
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is in use, the system will take a "integer divide zero trap" panic in
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the clock routine as soon as the time_offset becomes non-zero.
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time_constant defaults to 0. The only place it is set is in the ntp_adjtime
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system call, from the 'constant' element of the timex structure argument.
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----------------------------------------------------------------------------
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