Messages in this thread | | | Date | Wed, 07 Jan 2009 15:30:29 -0800 | From | Randy Dunlap <> | Subject | Re: [PATCH 2/3] sysrq documentation: document why the command header only is shown |
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Andy Whitcroft wrote: > Document the interactions between loglevel and the sysrq output. Also > document how to work round it should output on the console be required. > > Signed-off-by: Andy Whitcroft <apw@canonical.com> > --- > Documentation/sysrq.txt | 18 ++++++++++++++++++ > 1 files changed, 18 insertions(+), 0 deletions(-) > > diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt > index 265f637..a262ffb 100644 > --- a/Documentation/sysrq.txt > +++ b/Documentation/sysrq.txt > @@ -210,6 +210,24 @@ within a function called by handle_sysrq, you must be aware that you are in > a lock (you are also in an interrupt handler, which means don't sleep!), so > you must call __handle_sysrq_nolock instead. > > +* When I hit a sysrq combination only the header appears on the console, why?
* When I hit a sysrq key combination, only the header appears on the console. Why? > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > +Sysrq output is subject to the same console loglevel control as all > +other console output. This means that if the kernel was booted 'quiet' > +as is common on distro kernels the output may not appear on the actual > +console, even though it will appear in the dmesg buffer, and be accessible > +via the dmesg command and to the consumers of /proc/kmsg. As a specific > +exception the header line from the sysrq command is passed to all console > +consumers as if the current loglevel was maximum. If only the header > +is emitted it is almost cirtain that the kernel loglevel is too low.
certain
> +Should you require the output on the console channel then you will need > +to temporarily up the console loglevel using alt-sysrq-8 or: > + > + echo 8 > /proc/sysrq-trigger > + > +Remember to return the loglevel to normal after triggering the sysrq > +command you are interested in. > + > * I have more questions, who can I ask? > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > And I'll answer any questions about the registration system you got, also
-- ~Randy
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