[linuxsh-dev] Cache coherency issue

[NIIBE Y. <gn...@m1...>]

NIIBE Yutaka wrote:
 > We need cache flushing when process forks.  I think that this is the
 > bug in the mainline, I'll send a report to lkml (or MM-Bugzilla?).
 > When we forks, we set COW (copy-on-write) page to be write protected.
 > When doing that, we need to flush the cache (at least for SH-4, 
 > which has write-back cache). 

Sorry, this part is bogus, because before calling copy_page_range, 
dum_mmap calles flush_cache_mm, which flushes all the cache for the
process.  Please ignore this part (mm/memory.c).

Only this one, please:
 > Besides, in order to not having the alias absolutely, (1) I've changed
 > the use of __flush_wback_region for I/O into __flush_purge_region, and
 > (2) I've changed copy_user_page function so that it doesn't remain
 > data fetched.  This change does no harm for current implementation, 
 > but it is required by forthcoming change.
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