Prev: [PATCH 1/2] Add a common struct clk
Next: [PATCH 2/6] Mtd: fixed space after open parenthesis
From: qingyuan huang on 11 Jul 2010 22:50
����Recently, I read the kernel codes from 2.6.32 to 2.6.35. I have a
question about the positions of flush_dcache_page and bounce_copy_vec
methods in copy_to_high_bio_irq function in mm/bounce.c file. In my
opinion, flush_dcache_page is written before bounce_copy_vec in order
to set the destination page in bounce_copy_vec� PG_dcache_dirty bit in
some platforms which have not hardware cache coherence protocol. But
when I read the flush_dcache_page codes in ARM and MIPS, I found there
could be some exceptions in this function copy_to_high_bio_irq. Take
ARM as a example, the flush_dcache_page in ARM platform has two
execution paths:
path1: set_bit(PG_dcache_dirty, &page->flags) (deffer flushing until
in update_mmu_cache)
path2: __flush_dcache_page (mapping, page); if(mapping) __flush_icache_all();
If the codes run in path2 not path1, because the cache is flushed
before copy operation�, it could make a mistake in
copy_to_high_bio_irq function. At this situation, the I/D cache could
be incoherent, and the system could run the bad�instructions in i
cache. If�we�switch the positions of the two funcitons, we could not
meet this qustion and it could not�lower the performance.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
 | 
Pages: 1
Prev: [PATCH 1/2] Add a common struct clk
Next: [PATCH 2/6] Mtd: fixed space after open parenthesis