6 files changed, 18 insertions, 1 deletions

diff --git a/arch/um/Makefile b/arch/um/Makefile
index dbeab15e7bb7..ca40397017b9 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -77,7 +77,6 @@ include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS)
 KERNEL_DEFINES = $(strip -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
                          -Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES))
 KBUILD_CFLAGS += $(KERNEL_DEFINES)
-KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time,)
 
 PHONY += linux
 
diff --git a/arch/um/Makefile-i386 b/arch/um/Makefile-i386
index 561e373bd850..302cbe504543 100644
--- a/arch/um/Makefile-i386
+++ b/arch/um/Makefile-i386
@@ -32,4 +32,11 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 # an unresolved reference.
 cflags-y += -ffreestanding
 
+# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
+# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
+# 4.3.0 needs -funit-at-a-time for extern inline functions.
+KBUILD_CFLAGS += $(shell if [ $(call cc-version) -lt 0400 ] ; then \
+                        echo $(call cc-option,-fno-unit-at-a-time); \
+                        else echo $(call cc-option,-funit-at-a-time); fi ;)
+
 KBUILD_CFLAGS += $(cflags-y)
diff --git a/arch/um/Makefile-x86_64 b/arch/um/Makefile-x86_64
index 8ed362f93582..a9cd7e77a7ab 100644
--- a/arch/um/Makefile-x86_64
+++ b/arch/um/Makefile-x86_64
@@ -21,3 +21,6 @@ HEADER_ARCH := x86
 
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
 LINK-y += -m64
+
+# Do unit-at-a-time unconditionally on x86_64, following the host
+KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
diff --git a/arch/um/drivers/harddog_kern.c b/arch/um/drivers/harddog_kern.c
index a9ad4bd6d953..d332503fa1be 100644
--- a/arch/um/drivers/harddog_kern.c
+++ b/arch/um/drivers/harddog_kern.c
@@ -66,6 +66,7 @@ static int harddog_open(struct inode *inode, struct file *file)
         int err = -EBUSY;
         char *sock = NULL;
 
+        lock_kernel();
         spin_lock(&lock);
         if(timer_alive)
                 goto err;
@@ -82,9 +83,11 @@ static int harddog_open(struct inode *inode, struct file *file)
 
         timer_alive = 1;
         spin_unlock(&lock);
+        unlock_kernel();
         return nonseekable_open(inode, file);
 err:
         spin_unlock(&lock);
+        unlock_kernel();
         return err;
 }
 
diff --git a/arch/um/drivers/mmapper_kern.c b/arch/um/drivers/mmapper_kern.c
index 67b2f55a602f..eb240323c40a 100644
--- a/arch/um/drivers/mmapper_kern.c
+++ b/arch/um/drivers/mmapper_kern.c
@@ -16,6 +16,7 @@
 #include <linux/miscdevice.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include "mem_user.h"
 
@@ -77,6 +78,7 @@ out:
 
 static int mmapper_open(struct inode *inode, struct file *file)
 {
+        cycle_kernel_lock();
         return 0;
 }
 
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index 4949044773ba..6eabb7022a2d 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -7,6 +7,7 @@
  * of the GNU General Public License, incorporated herein by reference.
  */
 #include <linux/sched.h>
+#include <linux/smp_lock.h>
 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/interrupt.h>
@@ -33,6 +34,8 @@ static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
 
 static int rng_dev_open (struct inode *inode, struct file *filp)
 {
+        cycle_kernel_lock();
+
         /* enforce read-only access to this chrdev */
         if ((filp->f_mode & FMODE_READ) == 0)
                 return -EINVAL;