Am 17.01.2023 um 17:16 hat Warner Losh geschrieben:
> On Tue, Jan 17, 2023 at 6:52 AM Emanuele Giuseppe Esposito <
> eesposit@redhat.com> wrote:
>
> > QEMU does not compile when enabling clang's thread safety analysis
> > (TSA),
> > because some functions create wrappers for pthread mutexes but do
> > not use any TSA macro. Therefore the compiler fails.
> >
> > In order to make the compiler happy and avoid adding all the
> > necessary macros to all callers (lock functions should use
> > TSA_ACQUIRE, while unlock TSA_RELEASE, and this applies to allusers of
> > pthread_mutex_lock/pthread_mutex_unlock),
> > simply use TSA_NO_TSA to supppress such warnings.
>
> I'm not sure I understand this quite right. Maybe a clarifying question
> will help me understand: Why is this needed for bsd-user but not
> linux-user? How are they different here?
FreeBSD's pthread headers include TSA annotations for some functions
that force us to do something about them (for now: suppress the warnings
in their callers) before we can enable -Wthread-safety for the purposes
where we really want it. Without this, calling functions like
pthread_mutex_lock() would cause compiler errors.
glibc's headers don't contain such annotations, so the same is not
necessary on Linux
Thanks Kevin. With that explanation, these patches and their explanation make perfect sense now. Often when there's a patch to bsd-user but not linux-user, it's because bsd-user needs to do more in some way (which I try to keep up on).
In this case, it's because FreeBSD's libc is a bit ahead of the curve. So I understand why it's needed, and what I need to do next (though I think that I may have to wait for the rest of qemu to be annotated)...
It might be better, though, to put some of this information in the commit message so it isn't just on the mailing list. Just a suggestion: