Re: [RFC 0/2] tls: add macros for coroutine-safe TLS variables

[Philippe Mathieu-Daudé]

+Richard/Peter

On 10/25/21 16:07, 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.
> 
> 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.

Beside the point Daniel raised (shared libs) this sensible
approach LGTM.

> 
> Todo:
> - Convert all uses of __thread

$ git grep __thread | wc -l
55

:/

> - Extend checkpatch.pl to reject code that uses __thread
> 
> Stefan Hajnoczi (2):
>   tls: add macros for coroutine-safe TLS variables
>   util/async: replace __thread with QEMU TLS macros
> 
>  MAINTAINERS        |   1 +
>  include/qemu/tls.h | 142 +++++++++++++++++++++++++++++++++++++++++++++
>  util/async.c       |  12 ++--
>  3 files changed, 150 insertions(+), 5 deletions(-)
>  create mode 100644 include/qemu/tls.h
>