[Mesa-dev] [PATCH v3 1/2] configure.ac: Enable GLX_USE_TLS if possible.

[tf (mobile)]

Even if the system supports tls, the x server may not have been built with it.  As i recall, there is an issue with mismatching tls between x and drivers... Can a non-tls server load a tls driver?

Anyway, if there's an issue there, this check must be more complicated -- it can't be just, "does the system support this",  it would instead need to be "can the system support this and is it enabled in the x server."

IIRC Eric and ajax and Dan know more, but there should also be a discussion of this in the xorg-devel and/or mesa archives.

-tom

On 15.02.2012, at 12:41, zhigang.gong at linux.intel.com wrote:

> From: Zhigang Gong <zhigang.gong at linux.intel.com>
> 
> If the system support tls, we prefer to enable it by default
> just as xserver does. Actually, the checking code is copied
> from xserver/configure.ac.
> According to nobled's suggestion, move the checking before
> enable_asm. As if tls_model is not supported, then asm may
> can't work correctly. Then we check the tls model first,
> and if doesn't support it, we need to disable the asm code.
> Here is the reference:
> https://bugs.freedesktop.org/show_bug.cgi?id=35268
> 
> Signed-off-by: Zhigang Gong <zhigang.gong at linux.intel.com>
> Reviewed-by: Dan Nicholson <dbn.lists at gmail.com>
> ---
> acinclude.m4 |   41 +++++++++++++++++++++++++++++++++++++++++
> configure.ac |   25 ++++++++++++++++++++++---
> 2 files changed, 63 insertions(+), 3 deletions(-)
> 
> diff --git a/acinclude.m4 b/acinclude.m4
> index a5b389d..23805f3 100644
> --- a/acinclude.m4
> +++ b/acinclude.m4
> @@ -117,3 +117,44 @@ if test "$enable_pic" != no; then
> fi
> AC_SUBST([PIC_FLAGS])
> ])# MESA_PIC_FLAGS
> +
> +dnl TLS detection
> +AC_DEFUN([MESA_TLS],
> +[AC_MSG_CHECKING(for thread local storage (TLS) support)
> +AC_CACHE_VAL(ac_cv_tls, [
> +    ac_cv_tls=none
> +    keywords="__thread __declspec(thread)"
> +    for kw in $keywords ; do
> +        AC_TRY_COMPILE([int $kw test;], [], ac_cv_tls=$kw)
> +    done
> +])
> +AC_MSG_RESULT($ac_cv_tls)
> +
> +if test "$ac_cv_tls" != "none"; then
> +    STRICT_CFLAGS="-pedantic -Werror"
> +    # Add -Werror=attributes if supported (gcc 4.2 & later)
> +    AC_MSG_CHECKING([if $CC supports -Werror=attributes])
> +    save_CFLAGS="$CFLAGS"
> +    CFLAGS="$CFLAGS $STRICT_CFLAGS -Werror=attributes"
> +    AC_TRY_COMPILE([int test;], [],
> +                   [STRICT_CFLAGS="$STRICT_CFLAGS -Werror=attributes"
> +                    AC_MSG_RESULT([yes])],
> +                   [AC_MSG_RESULT([no])])
> +    CFLAGS="$save_CFLAGS $STRICT_CFLAGS"
> +
> +    AC_MSG_CHECKING(for tls_model attribute support)
> +    AC_CACHE_VAL(ac_cv_tls_model, [
> +        AC_TRY_COMPILE([int $ac_cv_tls __attribute__((tls_model("initial-exec"))) test;], [],
> +                       ac_cv_tls_model=yes, ac_cv_tls_model=no)
> +    ])
> +    AC_MSG_RESULT($ac_cv_tls_model)
> +
> +    if test "x$ac_cv_tls_model" = "xyes" ; then
> +        TLS=$ac_cv_tls' __attribute__((tls_model(\"initial-exec\")))'
> +    else
> +        TLS=$ac_cv_tls
> +    fi
> +    DEFINES="$DEFINES -DTLS=\"$TLS\""
> +    CFLAGS="$save_CFLAGS"
> +fi
> +])
> diff --git a/configure.ac b/configure.ac
> index b2b1ab8..3226a09 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -433,6 +433,11 @@ AC_SUBST([VG_LIB_GLOB])
> AC_SUBST([GLAPI_LIB_GLOB])
> 
> dnl
> +dnl Check tls model support
> +dnl
> +MESA_TLS
> +
> +dnl
> dnl Arch/platform-specific settings
> dnl
> AC_ARG_ENABLE([asm],
> @@ -446,6 +451,14 @@ ASM_FLAGS=""
> MESA_ASM_SOURCES=""
> GLAPI_ASM_SOURCES=""
> AC_MSG_CHECKING([whether to enable assembly])
> +
> +if test "x$ac_cv_tls_model" = "xno" ; then
> +dnl
> +dnl If tls model is not supported, disable asm.
> +dnl
> +    enable_asm=no
> +fi
> +
> test "x$enable_asm" = xno && AC_MSG_RESULT([no])
> # disable if cross compiling on x86/x86_64 since we must run gen_matypes
> if test "x$enable_asm" = xyes && test "x$cross_compiling" = xyes; then
> @@ -1102,9 +1115,15 @@ dnl
> 
> AC_ARG_ENABLE([glx-tls],
>     [AS_HELP_STRING([--enable-glx-tls],
> -        [enable TLS support in GLX @<:@default=disabled@:>@])],
> -    [GLX_USE_TLS="$enableval"],
> -    [GLX_USE_TLS=no])
> +        [enable TLS support in GLX @<:@default=auto@:>@])],
> +    [GLX_USE_TLS=$enableval
> +     if test "x$GLX_USE_TLS" = "xyes" && test "${ac_cv_tls}" = "none" ; then
> +        AC_MSG_ERROR([GLX with TLS support requested, but the compiler does not support it.])
> +     fi],
> +    [GLX_USE_TLS=no
> +     if test "${ac_cv_tls}" != "none" ; then
> +        GLX_USE_TLS=yes
> +     fi])
> AC_SUBST(GLX_TLS, ${GLX_USE_TLS})
> 
> AS_IF([test "x$GLX_USE_TLS" = xyes],
> -- 
> 1.7.4.4
> 
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