lto-plugin: use locking only for selected targets

  For now, support locking only for linux targets that are different from
riscv* where the target depends on libatomic (and fails during
bootstrap).

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

	PR lto/106170

lto-plugin/ChangeLog:

	* configure.ac: Configure HAVE_PTHREAD_LOCKING.
	* lto-plugin.c (LOCK_SECTION): New.
	(UNLOCK_SECTION): New.
	(claim_file_handler): Use the newly added macros.
	(onload): Likewise.
	* config.h.in: Regenerate.
	* configure: Regenerate.
---
 lto-plugin/config.h.in  |  4 ++--
 lto-plugin/configure    | 20 ++++++++++++++------
 lto-plugin/configure.ac | 17 +++++++++++++++--
 lto-plugin/lto-plugin.c | 30 ++++++++++++++++++++----------
 4 files changed, 51 insertions(+), 20 deletions(-)
  

On Thu, Jul 7, 2022 at 1:43 PM Martin Liška <mliska@suse.cz> wrote:
>
> For now, support locking only for linux targets that are different from
> riscv* where the target depends on libatomic (and fails during
> bootstrap).
>
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>
> Ready to be installed?

OK - that also resolves the mingw issue, correct?  I suppose we need
to be careful to not advertise v1 API (which includes threadsafeness)
when not HAVE_PTHREAD_LOCKING.

Thanks,
Richard.

> Thanks,
> Martin
>
>         PR lto/106170
>
> lto-plugin/ChangeLog:
>
>         * configure.ac: Configure HAVE_PTHREAD_LOCKING.
>         * lto-plugin.c (LOCK_SECTION): New.
>         (UNLOCK_SECTION): New.
>         (claim_file_handler): Use the newly added macros.
>         (onload): Likewise.
>         * config.h.in: Regenerate.
>         * configure: Regenerate.
> ---
>  lto-plugin/config.h.in  |  4 ++--
>  lto-plugin/configure    | 20 ++++++++++++++------
>  lto-plugin/configure.ac | 17 +++++++++++++++--
>  lto-plugin/lto-plugin.c | 30 ++++++++++++++++++++----------
>  4 files changed, 51 insertions(+), 20 deletions(-)
>
> diff --git a/lto-plugin/config.h.in b/lto-plugin/config.h.in
> index 029e782f1ee..bf269f000d2 100644
> --- a/lto-plugin/config.h.in
> +++ b/lto-plugin/config.h.in
> @@ -9,8 +9,8 @@
>  /* Define to 1 if you have the <memory.h> header file. */
>  #undef HAVE_MEMORY_H
>
> -/* Define to 1 if pthread.h is present. */
> -#undef HAVE_PTHREAD_H
> +/* Define if the system-provided pthread locking mechanism. */
> +#undef HAVE_PTHREAD_LOCKING
>
>  /* Define to 1 if you have the <stdint.h> header file. */
>  #undef HAVE_STDINT_H
> diff --git a/lto-plugin/configure b/lto-plugin/configure
> index aaa91a63623..7ea54e6008f 100755
> --- a/lto-plugin/configure
> +++ b/lto-plugin/configure
> @@ -6011,14 +6011,22 @@ fi
>
>
>  # Check for thread headers.
> -ac_fn_c_check_header_mongrel "$LINENO" "pthread.h" "ac_cv_header_pthread_h" "$ac_includes_default"
> -if test "x$ac_cv_header_pthread_h" = xyes; then :
> +use_locking=no
>
> -$as_echo "#define HAVE_PTHREAD_H 1" >>confdefs.h
> +case $target in
> +  riscv*)
> +    # do not use locking as pthread depends on libatomic
> +    ;;
> +  *-linux*)
> +    use_locking=yes
> +    ;;
> +esac
>
> -fi
> +if test x$use_locking = xyes; then
>
> +$as_echo "#define HAVE_PTHREAD_LOCKING 1" >>confdefs.h
>
> +fi
>
>  case `pwd` in
>    *\ * | *\    *)
> @@ -12091,7 +12099,7 @@ else
>    lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
>    lt_status=$lt_dlunknown
>    cat > conftest.$ac_ext <<_LT_EOF
> -#line 12094 "configure"
> +#line 12102 "configure"
>  #include "confdefs.h"
>
>  #if HAVE_DLFCN_H
> @@ -12197,7 +12205,7 @@ else
>    lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
>    lt_status=$lt_dlunknown
>    cat > conftest.$ac_ext <<_LT_EOF
> -#line 12200 "configure"
> +#line 12208 "configure"
>  #include "confdefs.h"
>
>  #if HAVE_DLFCN_H
> diff --git a/lto-plugin/configure.ac b/lto-plugin/configure.ac
> index c2ec512880f..69bc5139193 100644
> --- a/lto-plugin/configure.ac
> +++ b/lto-plugin/configure.ac
> @@ -88,8 +88,21 @@ AM_CONDITIONAL(LTO_PLUGIN_USE_SYMVER_GNU, [test "x$lto_plugin_use_symver" = xgnu
>  AM_CONDITIONAL(LTO_PLUGIN_USE_SYMVER_SUN, [test "x$lto_plugin_use_symver" = xsun])
>
>  # Check for thread headers.
> -AC_CHECK_HEADER(pthread.h,
> -  [AC_DEFINE(HAVE_PTHREAD_H, 1, [Define to 1 if pthread.h is present.])])
> +use_locking=no
> +
> +case $target in
> +  riscv*)
> +    # do not use locking as pthread depends on libatomic
> +    ;;
> +  *-linux*)
> +    use_locking=yes
> +    ;;
> +esac
> +
> +if test x$use_locking = xyes; then
> +  AC_DEFINE(HAVE_PTHREAD_LOCKING, 1,
> +           [Define if the system-provided pthread locking mechanism.])
> +fi
>
>  AM_PROG_LIBTOOL
>  ACX_LT_HOST_FLAGS
> diff --git a/lto-plugin/lto-plugin.c b/lto-plugin/lto-plugin.c
> index 635e126946b..cba58f5999b 100644
> --- a/lto-plugin/lto-plugin.c
> +++ b/lto-plugin/lto-plugin.c
> @@ -40,11 +40,7 @@ along with this program; see the file COPYING3.  If not see
>
>  #ifdef HAVE_CONFIG_H
>  #include "config.h"
> -#if !HAVE_PTHREAD_H
> -#error POSIX threads are mandatory dependency
>  #endif
> -#endif
> -
>  #if HAVE_STDINT_H
>  #include <stdint.h>
>  #endif
> @@ -59,7 +55,9 @@ along with this program; see the file COPYING3.  If not see
>  #include <unistd.h>
>  #include <fcntl.h>
>  #include <sys/types.h>
> +#if HAVE_PTHREAD_LOCKING
>  #include <pthread.h>
> +#endif
>  #ifdef HAVE_SYS_WAIT_H
>  #include <sys/wait.h>
>  #endif
> @@ -162,9 +160,18 @@ enum symbol_style
>    ss_uscore,   /* Underscore prefix all symbols.  */
>  };
>
> +#if HAVE_PTHREAD_LOCKING
>  /* Plug-in mutex.  */
>  static pthread_mutex_t plugin_lock;
>
> +#define LOCK_SECTION pthread_mutex_lock (&plugin_lock)
> +#define UNLOCK_SECTION pthread_mutex_unlock (&plugin_lock)
> +#else
> +
> +#define LOCK_SECTION
> +#define UNLOCK_SECTION
> +#endif
> +
>  static char *arguments_file_name;
>  static ld_plugin_register_claim_file register_claim_file;
>  static ld_plugin_register_all_symbols_read register_all_symbols_read;
> @@ -1270,18 +1277,18 @@ claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
>                               lto_file.symtab.syms);
>        check (status == LDPS_OK, LDPL_FATAL, "could not add symbols");
>
> -      pthread_mutex_lock (&plugin_lock);
> +      LOCK_SECTION;
>        num_claimed_files++;
>        claimed_files =
>         xrealloc (claimed_files,
>                   num_claimed_files * sizeof (struct plugin_file_info));
>        claimed_files[num_claimed_files - 1] = lto_file;
> -      pthread_mutex_unlock (&plugin_lock);
> +      UNLOCK_SECTION;
>
>        *claimed = 1;
>      }
>
> -  pthread_mutex_lock (&plugin_lock);
> +  LOCK_SECTION;
>    if (offload_files == NULL)
>      {
>        /* Add dummy item to the start of the list.  */
> @@ -1344,14 +1351,15 @@ claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
>         offload_files_last_lto = ofld;
>        num_offload_files++;
>      }
> -  pthread_mutex_unlock (&plugin_lock);
> +
> +  UNLOCK_SECTION;
>
>    goto cleanup;
>
>   err:
> -  pthread_mutex_lock (&plugin_lock);
> +  LOCK_SECTION;
>    non_claimed_files++;
> -  pthread_mutex_unlock (&plugin_lock);
> +  UNLOCK_SECTION;
>    free (lto_file.name);
>
>   cleanup:
> @@ -1429,11 +1437,13 @@ onload (struct ld_plugin_tv *tv)
>    struct ld_plugin_tv *p;
>    enum ld_plugin_status status;
>
> +#if HAVE_PTHREAD_LOCKING
>    if (pthread_mutex_init (&plugin_lock, NULL) != 0)
>      {
>        fprintf (stderr, "mutex init failed\n");
>        abort ();
>      }
> +#endif
>
>    p = tv;
>    while (p->tv_tag)
> --
> 2.36.1
>
  

Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org> writes:

>> +if test x$use_locking = xyes; then
>> +  AC_DEFINE(HAVE_PTHREAD_LOCKING, 1,
>> +           [Define if the system-provided pthread locking mechanism.])

This isn't even a sentence.  At least I cannot parse it.  Besides, it
seems to be misnamed since the test doesn't check if pthread_mutex_lock
and friends are present on the target, but if they should be used.

	Rainer
  

On 7/7/22 13:52, Rainer Orth wrote:
> Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> 
>>> +if test x$use_locking = xyes; then
>>> +  AC_DEFINE(HAVE_PTHREAD_LOCKING, 1,
>>> +           [Define if the system-provided pthread locking mechanism.])
> 
> This isn't even a sentence.  At least I cannot parse it.  Besides, it
> seems to be misnamed since the test doesn't check if pthread_mutex_lock
> and friends are present on the target, but if they should be used.

You are right, fixed in v2.

Martin

> 
> 	Rainer
>
  

On 7/7/22 13:46, Richard Biener wrote:
> OK - that also resolves the mingw issue, correct?  I suppose we need

Yes.

> to be careful to not advertise v1 API (which includes threadsafeness)
> when not HAVE_PTHREAD_LOCKING.

Will reflect that in the patch.

I'm going to push it now.

Martin