On Mon, 2010-10-04 at 15:37 -0500, Scott Wood wrote: > [Updated with Nick's current address; previous one bounced] > > On Mon, 4 Oct 2010 15:22:59 -0500 > Scott Wood <scottw...@freescale.com> wrote: > > > I'm seeing the in_atomic() check in page_cache_get_speculative() > > (linux/pagemap.h:138) fail when running e500 KVM with . > > Sorry, that should finish as "with CONFIG_DEBUG_VM." > > > It's coming > > from get_user_pages_fast(), from KVM's hva_to_pfn(). This is on kvm.git > > plus a few local patches that should be completely unrelated, but it > > looks like this code hasn't changed much in a couple years. > > > > Interrupts are disabled by get_user_pages_fast(), but apparently > > preemption was not separately disabled. The comment in > > page_cache_get_speculative() says that preemption disabling is done by > > rcu_read_lock(), and that "this function must be called inside the same > > rcu_read_lock() section as has been used to lookup the page in the > > pagecache radix-tree (or page table)". > > > > Where is this RCU lock supposed to be acquired? I don't see any RCU in > > arch/powerpc/mm/gup.c. Is it buried in some macro or function call? > >
Well, we shouldn't need the rcu lock if interrupts are off, at least that's my understanding... Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
