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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-09 22:34:26 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-09 22:34:26 +0300 |
commit | e9a83bd2322035ed9d7dcf35753d3f984d76c6a5 (patch) | |
tree | 66dc466ff9aec0f9bb7f39cba50a47eab6585559 /Documentation/watchdog/hpwdt.rst | |
parent | 7011b7e1b702cc76f9e969b41d9a95969f2aecaa (diff) | |
parent | 454f96f2b738374da4b0a703b1e2e7aed82c4486 (diff) | |
download | linux-e9a83bd2322035ed9d7dcf35753d3f984d76c6a5.tar.xz |
Merge tag 'docs-5.3' of git://git.lwn.net/linux
Pull Documentation updates from Jonathan Corbet:
"It's been a relatively busy cycle for docs:
- A fair pile of RST conversions, many from Mauro. These create more
than the usual number of simple but annoying merge conflicts with
other trees, unfortunately. He has a lot more of these waiting on
the wings that, I think, will go to you directly later on.
- A new document on how to use merges and rebases in kernel repos,
and one on Spectre vulnerabilities.
- Various improvements to the build system, including automatic
markup of function() references because some people, for reasons I
will never understand, were of the opinion that
:c:func:``function()`` is unattractive and not fun to type.
- We now recommend using sphinx 1.7, but still support back to 1.4.
- Lots of smaller improvements, warning fixes, typo fixes, etc"
* tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits)
docs: automarkup.py: ignore exceptions when seeking for xrefs
docs: Move binderfs to admin-guide
Disable Sphinx SmartyPants in HTML output
doc: RCU callback locks need only _bh, not necessarily _irq
docs: format kernel-parameters -- as code
Doc : doc-guide : Fix a typo
platform: x86: get rid of a non-existent document
Add the RCU docs to the core-api manual
Documentation: RCU: Add TOC tree hooks
Documentation: RCU: Rename txt files to rst
Documentation: RCU: Convert RCU UP systems to reST
Documentation: RCU: Convert RCU linked list to reST
Documentation: RCU: Convert RCU basic concepts to reST
docs: filesystems: Remove uneeded .rst extension on toctables
scripts/sphinx-pre-install: fix out-of-tree build
docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/
Documentation: PGP: update for newer HW devices
Documentation: Add section about CPU vulnerabilities for Spectre
Documentation: platform: Delete x86-laptop-drivers.txt
docs: Note that :c:func: should no longer be used
...
Diffstat (limited to 'Documentation/watchdog/hpwdt.rst')
-rw-r--r-- | Documentation/watchdog/hpwdt.rst | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/Documentation/watchdog/hpwdt.rst b/Documentation/watchdog/hpwdt.rst new file mode 100644 index 000000000000..94a96371113e --- /dev/null +++ b/Documentation/watchdog/hpwdt.rst @@ -0,0 +1,73 @@ +=========================== +HPE iLO NMI Watchdog Driver +=========================== + +for iLO based ProLiant Servers +============================== + +Last reviewed: 08/20/2018 + + + The HPE iLO NMI Watchdog driver is a kernel module that provides basic + watchdog functionality and handler for the iLO "Generate NMI to System" + virtual button. + + All references to iLO in this document imply it also works on iLO2 and all + subsequent generations. + + Watchdog functionality is enabled like any other common watchdog driver. That + is, an application needs to be started that kicks off the watchdog timer. A + basic application exists in tools/testing/selftests/watchdog/ named + watchdog-test.c. Simply compile the C file and kick it off. If the system + gets into a bad state and hangs, the HPE ProLiant iLO timer register will + not be updated in a timely fashion and a hardware system reset (also known as + an Automatic Server Recovery (ASR)) event will occur. + + The hpwdt driver also has the following module parameters: + + ============ ================================================================ + soft_margin allows the user to set the watchdog timer value. + Default value is 30 seconds. + timeout an alias of soft_margin. + pretimeout allows the user to set the watchdog pretimeout value. + This is the number of seconds before timeout when an + NMI is delivered to the system. Setting the value to + zero disables the pretimeout NMI. + Default value is 9 seconds. + nowayout basic watchdog parameter that does not allow the timer to + be restarted or an impending ASR to be escaped. + Default value is set when compiling the kernel. If it is set + to "Y", then there is no way of disabling the watchdog once + it has been started. + ============ ================================================================ + + NOTE: + More information about watchdog drivers in general, including the ioctl + interface to /dev/watchdog can be found in + Documentation/watchdog/watchdog-api.rst and Documentation/IPMI.txt. + + Due to limitations in the iLO hardware, the NMI pretimeout if enabled, + can only be set to 9 seconds. Attempts to set pretimeout to other + non-zero values will be rounded, possibly to zero. Users should verify + the pretimeout value after attempting to set pretimeout or timeout. + + Upon receipt of an NMI from the iLO, the hpwdt driver will initiate a + panic. This is to allow for a crash dump to be collected. It is incumbent + upon the user to have properly configured the system for kdump. + + The default Linux kernel behavior upon panic is to print a kernel tombstone + and loop forever. This is generally not what a watchdog user wants. + + For those wishing to learn more please see: + Documentation/kdump/kdump.rst + Documentation/admin-guide/kernel-parameters.txt (panic=) + Your Linux Distribution specific documentation. + + If the hpwdt does not receive the NMI associated with an expiring timer, + the iLO will proceed to reset the system at timeout if the timer hasn't + been updated. + +-- + + The HPE iLO NMI Watchdog Driver and documentation were originally developed + by Tom Mingarelli. |