RE: Mutual Exclusion in Kernel

RE: Mutual Exclusion in Kernel

[Ankit Jain]

hi

what is spin lock?

thanks

ankit 
--- "Dhiman, Gaurav" <Gaurav.Dhiman@ca.com> wrote: 
> 
> Use either semaphore or spin locks for mutual
> exclusion
> 
> Gaurav
> 
> 
> -----Original Message-----
> From: kernelnewbies-bounce@nl.linux.org
> [mailto:kernelnewbies-bounce@nl.linux.org] On Behalf
> Of Rakesh Jagota
> Sent: Wednesday, October 06, 2004 9:03 AM
> To: kernelnewbies
> Subject: Mutual Exclusion in Kernel
> 
> Hello All,
> 
> I have defined one array of structures in the kernel
> which can be seen
> by
> all the modules. Now I would like to have mutual
> exclusion , that is if
> any
> module is accessing the array ,no other module
> should not access the
> same
> array, since it is a global array.
> 
> Thanks in advance
> 
> Regards
> Rakesh
> 
> 
> --
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RE: Mutual Exclusion in Kernel

[Robin Doer]

Good morning!

Ankit Jain (ankitjain1580@yahoo.com) schrieb:
>
> hi
>
> what is spin lock?

http://en.wikipedia.org/wiki/Spin_lock

aka "busy waiting". A thread is polling <something> until <something> says
"ok" and the thread continues working.

>
> thanks
>
> ankit

Have fun,
Robin

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Re: Mutual Exclusion in Kernel

[kernel kernel]

Hi All,

Spin lock is a mutual exclusion strategy which is used in
Multiprocessor machanies.

When  i resource is not available for a  particular thread, it wont be
removed from TASK_RUNNING status and put into the corresponding event
Q. Instead it will loop around the processor, in closed cycles until
the resource is available.

So when the thread which currently owns the resource in other
processor leaves the resource, the loop thread can access the
resource.  This can avoid the Thundering Herd problem as well as the
overhead of pushing the thread  into the Event Q..

Thanks
Amrith


On Wed, 06 Oct 2004 10:43:20 +0200, Robin Doer <robin@robind.de> wrote:
> Good morning!
> 
> Ankit Jain (ankitjain1580@yahoo.com) schrieb:
> >
> > hi
> >
> > what is spin lock?
> 
> http://en.wikipedia.org/wiki/Spin_lock
> 
> aka "busy waiting". A thread is polling <something> until <something> says
> "ok" and the thread continues working.
> 
> >
> > thanks
> >
> > ankit
> 
> Have fun,
> Robin
> 
> 
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
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Re: Mutual Exclusion in Kernel

[Robin Doer]

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No!

You have to write your own busy-waiting-algorithm while the operating system 
provides you a semaphore.

A busy-waiting-algorithm can be compared with a two-state-semaphore (lock or 
unlock) but the concept of the semaphore is must more powerful. In theory an 
infinite number of states is possible. Thus you can control the access to a 
resource in different levels.

Am Mittwoch, 6. Oktober 2004 10:55 schrieben Sie:
> but this is like semaphore?
>
> thanks again
>
> ankit
>
>  --- Robin Doer <robin@robind.de> wrote:
> > Good morning!
> >
> > Ankit Jain (ankitjain1580@yahoo.com) schrieb:
> > > hi
> > >
> > > what is spin lock?
> >
> > http://en.wikipedia.org/wiki/Spin_lock
> >
> > aka "busy waiting". A thread is polling <something>
> > until <something> says
> > "ok" and the thread continues working.
> >
> > > thanks
> > >
> > > ankit
> >
> > Have fun,
> > Robin
> >
> > -
> > To unsubscribe from this list: send the line
> > "unsubscribe linux-newbie" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at
> > http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at
> > http://www.linux-learn.org/faqs
>
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