Re: [linuxsh-dev] Cache bug on SH-3/4

[David M. <da...@sn...>]

Hi Paul,

I just tried this on my 2.4.17 kernel on the 7751R/SH4 with no crash
and it output 0 as I suspect it is supposed to.  I can try some more
platforms/combos monday when I am back in the office if you like.

Not sure that it worked for me means much though,  could be just be the
cache state/entries are quite different between our platforms.

Cheers,
Davidm

Jivin Paul Mundt lays it down ...
> I've hit what looks to be another cache bug (looks like its an alias
> issue), and so far it seems to hit both SH-3 and 4. (I haven't tested
> SH-2 or 5 yet).
> 
> The problem pops up when doing an mmap() of /dev/zero and then reading
> from it, the read is sometimes 0, but most of the time ends up getting
> back garbage and promptly segfaulting.
> 
> I've attached my testcode for this as well. The fault happens right on
> the read.
> 
> I've managed to fix this on SH-4 (patch attached) by doing an all out
> flush_cache_all() after the activate_context() in switch_mm() .. not a
> very optimal solution, but seems to do the right thing for now.
> 
> Unfortunately this same fix doesn't help SH-3 any (after implicitly
> wrapping flush_cache_all() to cache_wback_all()).
> 
> Anyone seen this before?
> 
> Regards,
> 
> -- 
> Paul Mundt <pau...@ti...>
> TimeSys Corporation






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