On 10/25/21 7:07 AM, Stefan Hajnoczi wrote:
This is a preview of how we can solve the coroutines TLS problem. Coroutines
re-entered from another thread sometimes see stale TLS values. This happens
because compilers may cache values across yield points, so a value from the
previous thread will be used when the coroutine is re-entered in another
thread.
I'm not thrilled by this, but I guess it does work.
It could be worthwhile to add some inline asm instead for specific hosts -- one
instruction instead of an out-of-line call.
Serge Guelton developed this technique, see the first patch for details. I'm
submitting it for discussion before I go ahead with a full conversion of the
source tree.
Todo:
- Convert all uses of __thread
- Extend checkpatch.pl to reject code that uses __thread
Absolutely not. *Perhaps* one or two tls variables which are accessible by coroutines,
but there are plenty that have absolutely no relation. Especially everything related to
user-only execution.
r~
