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Atomic64 compatibility for 32-bit systems without kernel support.

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This patch is another step towards updating the code to handle the
32-bit kernels which I have not been regularly testing.  This changes
do not really impact the common case I'm expected which is the latest
kernel running on an x86_64 arch.

Until the linux-2.6.31 kernel the x86 arch did not have support for
64-bit atomic operations.  Additionally, the new atomic_compat.h support
for this case was wrong because it embedded a spinlock in the atomic
variable which must always and only be 64-bits total.  To handle these
32-bit issues we now simply fall back to the --enable-atomic-spinlock
implementation if the kernel does not provide the 64-bit atomic funcs.

The second issue this patch addresses is the DEBUG_KMEM assumption that
there will always be atomic64 funcs available.  On 32-bit archs this may
not be true, and actually that's just fine.  In that case the kernel will
will never be able to allocate more the 32-bits worth anyway.  So just
check if atomic64 funcs are available, if they are not it means this
is a 32-bit machine and we can safely use atomic_t's instead.
This commit is contained in:
Brian Behlendorf
2009-12-04 15:54:12 -08:00
parent db1aa22297
commit d04c8a563c
10 changed files with 396 additions and 788 deletions
Download Patch File Download Diff File Expand all files Collapse all files
config/spl-build.m4
+59 -48
View File
@@ -25,10 +25,9 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
SPL_AC_DEBUG_KMEM
SPL_AC_DEBUG_KMEM_TRACKING
SPL_AC_ATOMIC_SPINLOCK
SPL_AC_TYPE_UINTPTR_T
SPL_AC_TYPE_ATOMIC64_T
SPL_AC_TYPE_ATOMIC64_CMPXCHG
SPL_AC_TYPE_ATOMIC64_XCHG
SPL_AC_TYPE_UINTPTR_T
SPL_AC_3ARGS_INIT_WORK
SPL_AC_2ARGS_REGISTER_SYSCTL
SPL_AC_SET_SHRINKER
@@ -285,27 +284,6 @@ AC_DEFUN([SPL_AC_DEBUG_KMEM_TRACKING], [
AC_MSG_RESULT([$enable_debug_kmem_tracking])
])
dnl #
dnl # Use the atomic implemenation based on global spinlocks. This
dnl # should never be needed, however it has been left in place as
dnl # a fallback option in case problems are observed with directly
dnl # mapping to the native Linux atomic operations.
dnl #
AC_DEFUN([SPL_AC_ATOMIC_SPINLOCK], [
AC_ARG_ENABLE([atomic-spinlocks],
[AS_HELP_STRING([--enable-atomic-spinlocks],
[Atomic types use spinlocks @<:@default=no@:>@])],
[],
[enable_atomic_spinlocks=no])
AS_IF([test "x$enable_atomic_spinlocks" = xyes],
[AC_DEFINE([ATOMIC_SPINLOCK], [1],
[Atomic types use spinlocks])])
AC_MSG_CHECKING([whether atomic types use spinlocks])
AC_MSG_RESULT([$enable_atomic_spinlocks])
])
dnl #
dnl # SPL_LINUX_CONFTEST
dnl #
@@ -433,41 +411,55 @@ AC_DEFUN([SPL_CHECK_HEADER],
])
dnl #
dnl # 2.6.24 API change,
dnl # check if uintptr_t typedef is defined
dnl # Use the atomic implemenation based on global spinlocks. This
dnl # should only be needed by 32-bit kernels which do not provide
dnl # the atomic64_* API. It may be optionally enabled as a fallback
dnl # if problems are observed with the direct mapping to the native
dnl # Linux atomic operations. You may not disable atomic spinlocks
dnl # if you kernel does not an atomic64_* API.
dnl #
AC_DEFUN([SPL_AC_TYPE_UINTPTR_T],
[AC_MSG_CHECKING([whether kernel defines uintptr_t])
SPL_LINUX_TRY_COMPILE([
#include <linux/types.h>
],[
uintptr_t *ptr;
],[
AC_MSG_RESULT([yes])
AC_DEFINE(HAVE_UINTPTR_T, 1,
[kernel defines uintptr_t])
],[
AC_MSG_RESULT([no])
])
])
AC_DEFUN([SPL_AC_ATOMIC_SPINLOCK], [
AC_ARG_ENABLE([atomic-spinlocks],
[AS_HELP_STRING([--enable-atomic-spinlocks],
[Atomic types use spinlocks @<:@default=check@:>@])],
[],
[enable_atomic_spinlocks=check])
dnl #
dnl # 2.6.x API change,
dnl # check if atomic64_t typedef is defined
dnl #
AC_DEFUN([SPL_AC_TYPE_ATOMIC64_T],
[AC_MSG_CHECKING([whether kernel defines atomic64_t])
SPL_LINUX_TRY_COMPILE([
#include <asm/atomic.h>
],[
atomic64_t *ptr;
],[
AC_MSG_RESULT([yes])
have_atomic64_t=yes
AC_DEFINE(HAVE_ATOMIC64_T, 1,
[kernel defines atomic64_t])
[kernel defines atomic64_t])
],[
AC_MSG_RESULT([no])
have_atomic64_t=no
])
AS_IF([test "x$enable_atomic_spinlocks" = xcheck], [
AS_IF([test "x$have_atomic64_t" = xyes], [
enable_atomic_spinlocks=no
],[
enable_atomic_spinlocks=yes
])
])
AS_IF([test "x$enable_atomic_spinlocks" = xyes], [
AC_DEFINE([ATOMIC_SPINLOCK], [1],
[Atomic types use spinlocks])
],[
AS_IF([test "x$have_atomic64_t" = xno], [
AC_MSG_FAILURE(
[--disable-atomic-spinlocks given but required atomic64 support is unavailable])
])
])
AC_MSG_CHECKING([whether atomic types use spinlocks])
AC_MSG_RESULT([$enable_atomic_spinlocks])
AC_MSG_CHECKING([whether kernel defines atomic64_t])
AC_MSG_RESULT([$have_atomic64_t])
])
dnl #
@@ -508,6 +500,25 @@ AC_DEFUN([SPL_AC_TYPE_ATOMIC64_XCHG],
])
])
dnl #
dnl # 2.6.24 API change,
dnl # check if uintptr_t typedef is defined
dnl #
AC_DEFUN([SPL_AC_TYPE_UINTPTR_T],
[AC_MSG_CHECKING([whether kernel defines uintptr_t])
SPL_LINUX_TRY_COMPILE([
#include <linux/types.h>
],[
uintptr_t *ptr;
],[
AC_MSG_RESULT([yes])
AC_DEFINE(HAVE_UINTPTR_T, 1,
[kernel defines uintptr_t])
],[
AC_MSG_RESULT([no])
])
])
dnl #
dnl # 2.6.20 API change,
dnl # INIT_WORK use 2 args and not store data inside