Re: [PATCH v5 05/24] util: expose qemu_thread_set_name

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Jan 13, 2026 at 10:16:06AM +0100, Markus Armbruster wrote:
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> > The ability to set the thread name needs to be used in a number
> > of places, so expose the current impls as public methods.
> >
> > Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> > Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>
> > Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >  include/qemu/thread.h    |  1 +
> >  util/qemu-thread-posix.c | 26 ++++++++++++++++----------
> >  util/qemu-thread-win32.c | 13 ++++++++-----
> >  3 files changed, 25 insertions(+), 15 deletions(-)
> >
> > diff --git a/include/qemu/thread.h b/include/qemu/thread.h
> > index 3a286bb3ef..27b888ab0a 100644
> > --- a/include/qemu/thread.h
> > +++ b/include/qemu/thread.h
> > @@ -215,6 +215,7 @@ void *qemu_thread_join(QemuThread *thread);
> >  void qemu_thread_get_self(QemuThread *thread);
> >  bool qemu_thread_is_self(QemuThread *thread);
> >  G_NORETURN void qemu_thread_exit(void *retval);
> > +void qemu_thread_set_name(const char *name);
> >  
> >  struct Notifier;
> >  /**
> > diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> > index 7c985b5d38..b1c127dbe3 100644
> > --- a/util/qemu-thread-posix.c
> > +++ b/util/qemu-thread-posix.c
> > @@ -329,6 +329,21 @@ static void qemu_thread_atexit_notify(void *arg)
> >      notifier_list_notify(&thread_exit, NULL);
> >  }
> >  
> > +void qemu_thread_set_name(const char *name)
> > +{
> > +    /*
> > +     * Attempt to set the threads name; note that this is for debug, so
> > +     * we're not going to fail if we can't set it.
> > +     */
> > +# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> > +    pthread_setname_np(pthread_self(), name);
> > +# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
> > +    pthread_setname_np(name);
> > +# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
> > +    pthread_set_name_np(pthread_self(), name);
> > +# endif
> > +}
> > +
> >  typedef struct {
> >      void *(*start_routine)(void *);
> >      void *arg;
> > @@ -342,17 +357,8 @@ static void *qemu_thread_start(void *args)
> >      void *arg = qemu_thread_args->arg;
> >      void *r;
> >  
> > -    /* Attempt to set the threads name; note that this is for debug, so
> > -     * we're not going to fail if we can't set it.
> > -     */
> >      if (qemu_thread_args->name) {
> > -# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> > -        pthread_setname_np(pthread_self(), qemu_thread_args->name);
> > -# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
> > -        pthread_setname_np(qemu_thread_args->name);
> > -# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
> > -        pthread_set_name_np(pthread_self(), qemu_thread_args->name);
> > -# endif
> > +        qemu_thread_set_name(qemu_thread_args->name);
> >      }
> >      QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
> >      g_free(qemu_thread_args->name);
> 
> qemu_thread_set_name() is factored out.  No change in behavior.
> 
> > diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
> > index 9595a5b090..4d2d663a9a 100644
> > --- a/util/qemu-thread-win32.c
> > +++ b/util/qemu-thread-win32.c
> > @@ -225,6 +225,7 @@ struct QemuThreadData {
> >      void             *arg;
> >      short             mode;
> >      NotifierList      exit;
> > +    char             *name;
> >  
> >      /* Only used for joinable threads. */
> >      bool              exited;
> > @@ -266,6 +267,10 @@ static unsigned __stdcall win32_start_routine(void *arg)
> >      void *(*start_routine)(void *) = data->start_routine;
> >      void *thread_arg = data->arg;
> >  
> > +    if (data->name) {
> > +        qemu_thread_set_name(data->name);
> > +        g_clear_pointer(&data->name, g_free);
> > +    }
> >      qemu_thread_data = data;
> >      qemu_thread_exit(start_routine(thread_arg));
> >      abort();
> > @@ -316,7 +321,7 @@ void *qemu_thread_join(QemuThread *thread)
> >      return ret;
> >  }
> >  
> > -static void set_thread_description(HANDLE h, const char *name)
> > +void qemu_thread_set_name(const char *name)
> >  {
> >      g_autofree wchar_t *namew = NULL;
> >  
> > @@ -329,7 +334,7 @@ static void set_thread_description(HANDLE h, const char *name)
> >          return;
> >      }
> >  
> > -    SetThreadDescriptionFunc(h, namew);
> > +    SetThreadDescriptionFunc(GetCurrentThread(), namew);
> >  }
> >  
> >  void qemu_thread_create(QemuThread *thread, const char *name,
> > @@ -344,6 +349,7 @@ void qemu_thread_create(QemuThread *thread, const char *name,
> >      data->arg = arg;
> >      data->mode = mode;
> >      data->exited = false;
> > +    data->name = g_strdup(name);
> >      notifier_list_init(&data->exit);
> >  
> >      if (data->mode != QEMU_THREAD_DETACHED) {
> > @@ -355,9 +361,6 @@ void qemu_thread_create(QemuThread *thread, const char *name,
> >      if (!hThread) {
> >          error_exit(GetLastError(), __func__);
> >      }
> > -    if (name) {
> > -        set_thread_description(hThread, name);
> > -    }
> >      CloseHandle(hThread);
> >  
> >      thread->data = data;
> 
> This delays setting the thread name until the thread runs.  Fine, I
> guess, but I'd mention it in the commit message.
> 
> The new QemuThreadData member @name is non-null only between thread
> creation and thread name setting, unlike the other members under
> /* Passed to win32_start_routine.  */  Worth a comment?  Keep it alive
> until the thread dies?  Entirely up to you.

win32_start_routine never returns as it calls into qemu_thread_exit
so it is simpler to just free immediately after use. I'll comment
the struct.

> 
> Reviewed-by: Markus Armbruster <armbru@redhat.com>
> 

With regards,
Daniel
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