Hi Alan,
On Wed, Sep 20, 2006 at 01:08:45AM +0100, Alan Cox wrote:
> Ar Maw, 2006-09-19 am 13:54 -0400, ysgrifennodd Mathieu Desnoyers:
> > Very good idea.. However, overwriting the second instruction with a jump could
> > be dangerous on preemptible and SMP kernels, because we never know if a thread
> > has an IP in any of its contexts that would return exactly at the middle of the
> > jump.
>
> No: on x86 it is the *same* case for all of these even writing an int3.
> One byte or a megabyte,
>
> You MUST ensure that every CPU executes a serializing instruction before
> it hits code that was modified by another processor. Otherwise you get
> CPU errata and the CPU produces results which vendors like to describe
> as "undefined".
Are you referring to Intel erratum "unsynchronized cross-modifying code"
- where it refers to the practice of modifying code on one processor
where another has prefetched the unmodified version of the code.
Thanks
Prasanna
>
> Thus you have to serialize, and if you are serializing it really doesn't
> matter if you write a byte, a paragraph or a page.
>
--
Prasanna S.P.
Linux Technology Center
India Software Labs, IBM Bangalore
Email: [email protected]
Ph: 91-80-41776329
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
