What's MMU context?

What's MMU context?

[Wang Yong]

as the source code of linuxPPC, there is a global variable named 
next_mmu_context which is increased by one at each time of create a new
process. what does this mean and what is mmu context? it appears there
is not any mmu context in i386.

Wang


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Re: What's MMU context?

[Dan Malek]

Wang Yong wrote:
> 
> as the source code of linuxPPC, there is a global variable named
> next_mmu_context which is increased by one at each time of create a new
> process. what does this mean and what is mmu context?


I intened to use it on the 8xx processors, as they have an address
space id that allows a TLB optimization so you don't have to
invalidate the entire TLB on context switches.  I assume the
MIPS folks use it as well, since that is where I first used
such an optimization (in an OS other than Linux).  Unfortunately,
the ratio of entries to ASIDs is wrong for my original MIPS-like
algorithm to work, and I never got around to writing something
new.

This was already part of the Linux/PPC port when I started the 8xx
work, and I don't know if other processors use it or if it was
just part of the generic port that was maintained.


	-- Dan

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Re: What's MMU context?

[Wang Yong]

Dan Malek wrote:
> I intened to use it on the 8xx processors, as they have an address
> space id that allows a TLB optimization so you don't have to
> invalidate the entire TLB on context switches.  I assume the

  is this context contained in TLB entry? if yes, do you mean the
entries
  belong to other processes other the current one should not be replaced
  because it contains the integer ID named context?

  the TLB Entry of PPC401D2 contains lower 8 bit of PID. so it doesn't 
  need to flush all entries out when processing task switch. taking this
  into consider, if context of MMU is not useful any more?

  Thank you.
  Wang


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Debugging with thread(s)

[Claude Robitaille]

Hi,

anybody has tried to debug an application that uses thread
using GUI frontend to gdb? I have try code_medic and kdbg
but in both cases, when I execute pthread_create I get an
unknown signal and the breakpoints I set in the called
(created) thread do not activate. I might have problem
with my code but I tried to put a while(1); right after
a printf just at the beginning of the created thread. I
put a breakpoint on the printf but I do get an ouput
in the program output window. (I also put a while(1);
in the calling code, just to make sure). I think, somehow,
the GUIs do not support threads. Any idea?

Claude


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Re: Debugging with thread(s)

[Frank McPherson]

Claude Robitaille wrote:

> anybody has tried to debug an application that uses thread
> using GUI frontend to gdb? ... I execute pthread_create I get an
> unknown signal and the breakpoints I set in the called
> (created) thread do not activate. 

I get the same behavior when using gdb without any frontend.  Pthreads
seems to use real-time signals (32 and higher), and though the
documentation for gdb indicates it should be able to handle them, I
haven't been able to get it to work.  I posted a query about this
yesterday called "real-time signals, gdb".    

It has been suggested to me by another list member that the signal
handling code in the Linux kernel may be seriously deficient, and
aggrevating if not outright causing this problem.  I haven't had a
chance yet to look and see if that's the case. 

Has anyone else had success debugging threads with gdb? 

-Frank

-- 
Frank H. McPherson IV
W118 Embedded Solutions Team
The MITRE Corporation
703-883-5404

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Thread and malloc

[Claude Robitaille]

Hi,

I am getting segmentation faults in malloc when using threads. I have
updated my kernel to 2.2.14pre6, gcc, gdb (to 4.18), etc. I try both
code_medic and ddd. Is malloc thread safe? A book I am reading indicates
that some malloc are thread safe and some others are not. But the book
is not Linux specific.

The Web pages I have found so far are pretty old and mostly talk about
LinuxThread (for 2.0.X). The man pages for malloc, etc. do not indicate
anything about thread friendlyness... (and they would probably out of date
anyway....). Is there a good place for information about thread in Linux?
Anyboady has a idea why I an getting faults in malloc?

Thanks

Claude


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