Re: [PATCH 2/3] bsd-user/mmap: use TSA_NO_TSA to suppress clang TSA warnings

[Kevin Wolf <kwolf@redhat.com>]

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.

Kevin