Hi Srivatsa,<br><br><div class="gmail_quote">On Wed, Apr 18, 2012 at 1:57 PM, Srivatsa S. Bhat <span dir="ltr"><<a href="mailto:srivatsa.bhat@linux.vnet.ibm.com">srivatsa.bhat@linux.vnet.ibm.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="im">On 04/18/2012 01:38 PM, Arun KS wrote:<br>
<br>
> Hi Dave,<br>
><br>
> Thanks for your reply.<br>
><br>
> On Wed, Apr 18, 2012 at 1:01 PM, Dave Hylands <<a href="mailto:dhylands@gmail.com">dhylands@gmail.com</a><br>
</div><div class="im">> <mailto:<a href="mailto:dhylands@gmail.com">dhylands@gmail.com</a>>> wrote:<br>
><br>
> Hi Arun,<br>
><br>
> On Tue, Apr 17, 2012 at 11:44 PM, Arun KS <<a href="mailto:getarunks@gmail.com">getarunks@gmail.com</a><br>
</div><div class="im">> <mailto:<a href="mailto:getarunks@gmail.com">getarunks@gmail.com</a>>> wrote:<br>
> ><br>
> > Hello Guys,<br>
> ><br>
> > System is working normal after this BUG.<br>
> > PC is at 0x400b4614, probably a mmaped address.<br>
> ><br>
> > Just wondering how can this BUG happen when a process is running<br>
> in user<br>
> > space.<br>
> ><br>
> > Can it be something like this<br>
> > 1) enter to kernel from userspace through some system call.<br>
> > 2) kernel disables the interrupt and return to user space.<br>
><br>
> Don't do that<br>
><br>
><br>
> I don't do that. This scenario mentioned is a just a wild guess.<br>
><br>
><br>
> > 3) and now it can happen in user space?<br>
><br>
> Because something in userspace made a blocking call which would cause<br>
> a context switch to occur and your driver erroneously left interrupts<br>
> disabled.<br>
><br>
> In that case, my system should have been unstable afterwards if<br>
> interrupts are left disabled. But that is not happening.<br>
><br>
> If we return to user space with interrupts disabled, can we switch back<br>
> again to kernel using a system cal(because interrupts are already disabled)?<br>
><br>
<br>
<br>
</div>Depends on how many CPUs you have - AFAICS the "interrupts disabled"<br>
discussion above applies to a single CPU.. so if you have other CPUs on your<br>
system, you could probably use the system for a little more time.<br>
<br>
<br></blockquote><div>Hmm.. I have uniprocessor. <br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
There is a simple way to check if interrupts are indeed disabled as<br>
hypothesised: turn on the hard-lockup detector (See<br>
Documentation/lockup-watchdogs.txt for details on what it is and what<br>
config options you have to enable). You can even turn on the soft-lockup<br>
detector and see what you get. Setting the option to panic on hard-lockup/<br>
soft-lockup/hung tasks would be even better, to debug the issue.<br></blockquote><div><br>Thanks for the pointers. I ll try this out.<br><br>Arun <br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
Regards,<br>
Srivatsa S. Bhat<br>
<br>
</blockquote></div><br>