Re: [Fwd: [Fwd: Re: realtime-preempt for MIPS - compile problem with rwsem]]

[Daniel Walker <dwalker@mvista.com>]

It's a good idea to have it set to !PREEMPT_RT since it uses a
spinlock_t which becomes a mutex in PREEMPT_RT. With that in mind I
don't think it would work well, or at all with PREEMPT_RT enabled. 

Daniel


On Thu, 2006-06-29 at 09:30 -0600, Ryan McAvoy wrote:
> Hi,
> 
> I have now tried the 2.6.17 kernel (from linux-mips.org) with
> 2.6.17-rt1 plus the patches provided by Manish, and it works!
> 
> That is, it boots and is apparantly stable.  None of the procedures
> that would cause my 2.6.15 and 2.6.16 rt kernels to hang reliably hang
> this kernel.  As well, it ran over night and is still up.  (The other
> rt kernels I built would hang within hours even if left idle).
> 
> With respect to my original question regarding
> CONFIG_RWSEM_GENERIC_SPINLOCK, I have this option turned off in my
> configuration.  (Still have "depends on !PREEMPT_RT for that option).
> include/asm-mips/rwsem.h still calls rwsem_down_read_failed which is
> still not defined since lib/rwsem.c is not compiled.
> But, I don't encounter the link errors in this kernel because the two
> offending inline functions in include/asm-mips/rwsem.h __down_read and
> __down_write do not seem to be called from anywhere.
> 
> Ryan McAvoy
> 
> On 6/21/06, Manish Lachwani <mlachwani@mvista.com> wrote:
> > Hi !
> >
> > I have sent a MIPS patch to Ingo and Thomas just yesterday to support
> > realtime on MIPS in 2.6.17 and using the 2.6.17-rt1 patch. I have got
> > that patch working on Broadcom SWARM board (32-bit UP/SMP).
> >
> > Try this out and let me know. I have run some stability tests on this
> > kernel and have not noticed any hangs so far. So, it will be interesting
> > to flush out any bugs.
> >
> > Thanks
> > Manish Lachwani
> >
> >
> >
> > ---------- Forwarded message ----------
> > From: Daniel Walker <dwalker@mvista.com>
> > To: mlachwani@mvista.com
> > Date: Wed, 21 Jun 2006 09:31:59 -0700
> > Subject: [Fwd: Re: realtime-preempt for MIPS - compile problem with rwsem]
> >
> >
> >
> >
> > ---------- Forwarded message ----------
> > From: "Ryan McAvoy" <ryan.sed@gmail.com>
> > To: "Steven Rostedt" <rostedt@goodmis.org>
> > Date: Wed, 21 Jun 2006 10:12:29 -0600
> > Subject: Re: realtime-preempt for MIPS - compile problem with rwsem
> > On 6/21/06, Steven Rostedt wrote:
> >
> > http://groups.google.com/group/linux.kernel/browse_frm/thread/1559667001b7da2d/2558b539a5adc660?lnk=st&q=realtime+preempt+mips&rnum=2&hl=en#2558b539a5adc660
> > > > In the more common hangs though, I get no output.
> > >
> > > That output looks like it had a deadlock on the serial output of sysrq
> > > key.  But that back trace looks screwy.
> > >
> >
> > That problem actually went away with 2.6.16.  All the others remained
> > unfortunately.  (I was not that concerned about that one ... I can
> > avoid it just by not sending a sysrq ;-).  I posted it though since I
> > did actually have output with that hang).
> >
> > >
> > > Perhaps you can post all the changes you made as a patch to see if
> > > something else is wrong.  It might also be best to see if you can get the
> > > latest working (2.6.17-rtX) and work your way backwards to the kernel
> > > version you really need.
> > >
> >
> > I will post the other changes soon.  (I am not at the office where I
> > am working on this yet this morning).  I will also try 2.6.17.
> > Thanks.
> >
> > Ryan
> > -
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> >
> >

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