%fs on i386, %gs on amd64 registers, before using them. Otherwise, it
might be invalid/garbage, eg. IPI can interrupt userspace.
- Explicitly initialize per-CPU emap generation number.
Thanks <drochner> for reporting and testing of patch.
activity of other threads will perform the TLB flush for the processes using
emap as a side effect. To track that, global and per-CPU generation numbers
are used. This idea was suggested by Andrew Doran; various improvements to
it by me. Notes:
- For now, zero-copy on pipe is not yet enabled.
- TCP socket code would likely need more work.
- Additional UVM loaning improvements are needed.
Proposed on <tech-kern>, silence there.
Quickly reviewed by <ad>.
