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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Sorry if this has been covered before – I for one
could make use of that old list tarball if it were available.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am interested in using the interrupts controlled by
MSR[CE], specifically to help debug Watchdog timeout and PCI hang issues and
perhaps ultimately recover from them somehow. While I am able to achieve
some level of operation a quick browse of 2.6.8 makes me very nervous that I
may be re-inventing the wheel because it now includes the code to properly load
a 32 bit MSR_KERNEL setting but does not appear to actually use either of the
MSR[CE] controlled vectors (Watchdog, CriticalInput).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>- Are there patches available that somehow use either
Critical Input or Watchdog for something other than “unknown?”
I would not want to do anything that conflicts too badly with some low-latency
interrupt scheme for instance.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>- Has a back-port of the updated 32 bit MSR_KERNEL handling
to 2.4 been done already? I did this before realizing it was already done
in 2.6.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>- Is there any version that has normal IRQ handling smart
enough to leave critical interrupts alone? I had to resort to the rather
ugly trick of registering a dummy handler on IRQ 31 (UIC1 CI cascade) to keep
it from getting disabled.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>- Has anyone ever considered a patch that replaces the
normal HW exception handling with an immediate panic? For an embedded
system continuing to run after one or more user space processes has been
terminated does not seem to be an optimal behavior.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>- Are patches being accepted for 2.4, or is everything 2.6
now?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>What I am up to:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Situation:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The board I am working on is subject to random re-boots due
to Watchdog timeouts. Some of these are due to driver bugs (500mS udelay’s,
waiting forever for stuff that never happens etc), and others are due to PCI
devices that insist on claiming split transactions and then waiting several
seconds before responding. These situations are of course very rare and
almost impossible to duplicate so a JTAG debugger is out of the question.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Proposed solution:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Install an interrupt hander that captures the register dump
and stack trace whenever a watchdog or PCI error occurs. Since there is
no choice for the watchdog and the PCI errors could happen during interrupt top
halves or with interrupts disabled both situations pretty much require the use
of Critical Exceptions.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The PCI error capture is not completely redundant because
some of my boards have a bridge that can be configured to time out and abort
the offending transactions. Doing this without the handler however just
makes my problems harder to debug by allowing the driver to continue for who
knows how long before crashing.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>For now I just capture the trace and then panic the kernel
(cheap and easy HA solution) to “recover”. Longer term I may
try to develop a mechanism to allow drivers to register for some sort of
notification and recover more gracefully.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>David<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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