On 10/27/2010 10:54 AM, Peter Zijlstra wrote:
Christoph reported a nice splat which illustrated a race in the new stack based kmap_atomic implementation. The problem is that we pop our stack slot before we're completely done resetting its state -- in particular clearing the PTE (sometimes that's CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear the PTE used for the last slot, that interrupt can reuse the slot in a dirty state, which triggers a BUG in kmap_atomic(). Fix this by introducing kmap_atomic_idx() which reports the current slot index without actually releasing it and use that to find the PTE and delay the _pop() until after we're completely done. Reported-by: Christoph Hellwig<hch@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra<a.p.zijlstra@xxxxxxxxx>
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