Atomic64 compatibility for 32-bit systems without kernel support.

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.

1 files changed, 8 insertions, 1 deletions

diff --git a/include/sys/atomic.h b/include/sys/atomic.h
index 7a741de17..f522781fc 100644
--- a/include/sys/atomic.h
+++ b/include/sys/atomic.h
@@ -30,7 +30,14 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <sys/types.h>
-#include <asm/atomic_compat.h>
+
+#ifndef HAVE_ATOMIC64_CMPXCHG
+#define atomic64_cmpxchg(v, o, n)       (cmpxchg(&((v)->counter), (o), (n)))
+#endif
+
+#ifndef HAVE_ATOMIC64_XCHG
+#define atomic64_xchg(v, n)             (xchg(&((v)->counter), n))
+#endif
 
 /*
  * Two approaches to atomic operations are implemented each with its