Re: [PULL 15/26] configure, meson: move pthread_setname_np checks to Meson

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

On Thu, Oct 14, 2021 at 06:29:27PM +0200, Paolo Bonzini wrote:
> This makes the pthreads check dead in configure, so remove it
> as well.

This change appears broken

On v6.1.0

$ grep SETNAME_NP build/config-host.h
#define CONFIG_PTHREAD_SETNAME_NP_W_TID 1

While on git master

$ grep SETNAME_NP build/config-host.h
#define CONFIG_PTHREAD_SETNAME_NP_WO_TID
#define CONFIG_PTHREAD_SETNAME_NP_W_TID


it shoudn't be possible to have both these configs
satisfied as they're 2 completely different impls.

In the meson-log.txt we can see both tests passing, but with
warnings

  /home/berrange/src/virt/qemu/build/meson-private/tmpt191k3q1/testfile.c:9:5: warning: implicit declaration of function 'pthread_setname_np'; did you mean 'pthread_setcanceltype'? [-Wimplicit-function-declaration]

So it isn't actually validating the function parameter
signature, and then link is succeeding because the linker
doesn't care about the incompatible function signatures.

Peter meanwhile reports that he gets no pthread_Setname_np
at all, and his meson-build.log shows -Werror set. This
causes the missing fnuction signature to cause tests to
fail in both cases.

The original config.log shows _GNU_SOURCE being defined
for these tests, which would get the function signture
defined.

> 
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> Message-Id: <20211007130829.632254-9-pbonzini@redhat.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  configure                | 78 ----------------------------------------
>  meson.build              | 23 ++++++++++++
>  util/qemu-thread-posix.c |  5 ++-
>  3 files changed, 25 insertions(+), 81 deletions(-)
> 
> diff --git a/configure b/configure
> index e78f58978f..c7e95e59cc 100755
> --- a/configure
> +++ b/configure
> @@ -3148,71 +3148,6 @@ if test "$modules" = yes; then
>      fi
>  fi
>  
> -##########################################
> -# pthread probe
> -PTHREADLIBS_LIST="-pthread -lpthread -lpthreadGC2"
> -
> -pthread=no
> -cat > $TMPC << EOF
> -#include <pthread.h>
> -static void *f(void *p) { return NULL; }
> -int main(void) {
> -  pthread_t thread;
> -  pthread_create(&thread, 0, f, 0);
> -  return 0;
> -}
> -EOF
> -if compile_prog "" "" ; then
> -  pthread=yes
> -else
> -  for pthread_lib in $PTHREADLIBS_LIST; do
> -    if compile_prog "" "$pthread_lib" ; then
> -      pthread=yes
> -      break
> -    fi
> -  done
> -fi
> -
> -if test "$mingw32" != yes && test "$pthread" = no; then
> -  error_exit "pthread check failed" \
> -      "Make sure to have the pthread libs and headers installed."
> -fi
> -
> -# check for pthread_setname_np with thread id
> -pthread_setname_np_w_tid=no
> -cat > $TMPC << EOF
> -#include <pthread.h>
> -
> -static void *f(void *p) { return NULL; }
> -int main(void)
> -{
> -    pthread_t thread;
> -    pthread_create(&thread, 0, f, 0);
> -    pthread_setname_np(thread, "QEMU");
> -    return 0;
> -}
> -EOF
> -if compile_prog "" "$pthread_lib" ; then
> -  pthread_setname_np_w_tid=yes
> -fi
> -
> -# check for pthread_setname_np without thread id
> -pthread_setname_np_wo_tid=no
> -cat > $TMPC << EOF
> -#include <pthread.h>
> -
> -static void *f(void *p) { pthread_setname_np("QEMU"); return NULL; }
> -int main(void)
> -{
> -    pthread_t thread;
> -    pthread_create(&thread, 0, f, 0);
> -    return 0;
> -}
> -EOF
> -if compile_prog "" "$pthread_lib" ; then
> -  pthread_setname_np_wo_tid=yes
> -fi
> -
>  ##########################################
>  # libssh probe
>  if test "$libssh" != "no" ; then
> @@ -4498,19 +4433,6 @@ if test "$debug_mutex" = "yes" ; then
>    echo "CONFIG_DEBUG_MUTEX=y" >> $config_host_mak
>  fi
>  
> -# Hold two types of flag:
> -#   CONFIG_THREAD_SETNAME_BYTHREAD  - we've got a way of setting the name on
> -#                                     a thread we have a handle to
> -#   CONFIG_PTHREAD_SETNAME_NP_W_TID - A way of doing it on a particular
> -#                                     platform
> -if test "$pthread_setname_np_w_tid" = "yes" ; then
> -  echo "CONFIG_THREAD_SETNAME_BYTHREAD=y" >> $config_host_mak
> -  echo "CONFIG_PTHREAD_SETNAME_NP_W_TID=y" >> $config_host_mak
> -elif test "$pthread_setname_np_wo_tid" = "yes" ; then
> -  echo "CONFIG_THREAD_SETNAME_BYTHREAD=y" >> $config_host_mak
> -  echo "CONFIG_PTHREAD_SETNAME_NP_WO_TID=y" >> $config_host_mak
> -fi
> -
>  if test "$bochs" = "yes" ; then
>    echo "CONFIG_BOCHS=y" >> $config_host_mak
>  fi
> diff --git a/meson.build b/meson.build
> index e8e728bf72..26fc4e5792 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1584,6 +1584,29 @@ config_host_data.set('CONFIG_POSIX_MADVISE', cc.links(gnu_source_prefix + '''
>    #include <sys/mman.h>
>    #include <stddef.h>
>    int main(void) { return posix_madvise(NULL, 0, POSIX_MADV_DONTNEED); }'''))
> +
> +config_host_data.set('CONFIG_PTHREAD_SETNAME_NP_W_TID', cc.links('''
> +  #include <pthread.h>
> +
> +  static void *f(void *p) { return NULL; }
> +  int main(void)
> +  {
> +    pthread_t thread;
> +    pthread_create(&thread, 0, f, 0);
> +    pthread_setname_np(thread, "QEMU");
> +    return 0;
> +  }''', dependencies: threads))
> +config_host_data.set('CONFIG_PTHREAD_SETNAME_NP_WO_TID', cc.links('''
> +  #include <pthread.h>
> +
> +  static void *f(void *p) { pthread_setname_np("QEMU"); return NULL; }
> +  int main(void)
> +  {
> +    pthread_t thread;
> +    pthread_create(&thread, 0, f, 0);
> +    return 0;
> +  }''', dependencies: threads))
> +
>  config_host_data.set('CONFIG_SIGNALFD', cc.links(gnu_source_prefix + '''
>    #include <sys/signalfd.h>
>    #include <stddef.h>
> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index 6c5004220d..e1225b63bd 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -23,7 +23,8 @@ void qemu_thread_naming(bool enable)
>  {
>      name_threads = enable;
>  
> -#ifndef CONFIG_THREAD_SETNAME_BYTHREAD
> +#if !defined CONFIG_PTHREAD_SETNAME_NP_W_TID && \
> +    !defined CONFIG_PTHREAD_SETNAME_NP_WO_TID
>      /* This is a debugging option, not fatal */
>      if (enable) {
>          fprintf(stderr, "qemu: thread naming not supported on this host\n");
> @@ -522,7 +523,6 @@ static void *qemu_thread_start(void *args)
>      void *arg = qemu_thread_args->arg;
>      void *r;
>  
> -#ifdef CONFIG_THREAD_SETNAME_BYTHREAD
>      /* 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.
>       */
> @@ -533,7 +533,6 @@ static void *qemu_thread_start(void *args)
>          pthread_setname_np(qemu_thread_args->name);
>  # endif
>      }
> -#endif
>      QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
>      g_free(qemu_thread_args->name);
>      g_free(qemu_thread_args);
> -- 
> 2.31.1
> 
> 
> 

Regards,
Daniel
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