Re: [PATCH] ata: fix sleep-while-holding-spinlock in sata_nv
From: Robert Hancock
Date: Wed May 21 2008 - 10:33:47 EST
rjan van de Ven wrote:
I'm not certain this is safe to do it quite this way. It would be
better to keep that spinlock held so that no operations could be in
progress on either port while these operations are happening.
blk_bounce_limit can sleep. that's just a fact of life ;(
Now it can, for no reason. Under the conditions it was used before, it
never could.
It would be better to fix the regression from
419c434c35614609fd0c79d335c134bf4b88b30b in block/blk_settings.c that
resulted in the blk_queue_bounce_limit allocation wrongly allocating
emergency ISA pages in the first place as a 32-bit DMA mask does not
need them.
the condition under which it sleeps might be slightly buggy on your
exact x86 machine... but that doesn't mean that that is guaranteed to
be so forever going forward.... it's still a sleeping function.
More than slightly buggy, I think.. It seems like it is going to be
bouncing block layer accesses to devices with 32-bit DMA masks through
the 16MB ZONE_DMA. If that's what's actually going on, I'm surprised
there haven't been more regression reports. The fact that the function
now sleeps when it didn't before is the least of the problems here..
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