[PATCH] uml: locking documentation
Some locking documentation and a cleanup. uml_exitcode is copied into a local
before sprintf sees it, in case sprintf does anything non-atomic with it.
The rest are comments about why certain globals don't need any kind of
locking.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/drivers/null.c b/arch/um/drivers/null.c
index 3683ed4..9016c68 100644
--- a/arch/um/drivers/null.c
+++ b/arch/um/drivers/null.c
@@ -8,6 +8,7 @@
#include "chan_user.h"
#include "os.h"
+/* This address is used only as a unique identifer */
static int null_chan;
static void *null_init(char *str, int device, const struct chan_opts *opts)
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index ae99094..73b2bdd 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -20,6 +20,10 @@
#define RNG_MISCDEV_MINOR 183 /* official */
+/* Changed at init time, in the non-modular case, and at module load
+ * time, in the module case. Presumably, the module subsystem
+ * protects against a module being loaded twice at the same time.
+ */
static int random_fd = -1;
static int rng_dev_open (struct inode *inode, struct file *filp)
diff --git a/arch/um/drivers/stderr_console.c b/arch/um/drivers/stderr_console.c
index 6d2cf32..9115392 100644
--- a/arch/um/drivers/stderr_console.c
+++ b/arch/um/drivers/stderr_console.c
@@ -9,6 +9,8 @@
/*
* Don't register by default -- as this registeres very early in the
* boot process it becomes the default console.
+ *
+ * Initialized at init time.
*/
static int use_stderr_console = 0;
diff --git a/arch/um/drivers/stdio_console.c b/arch/um/drivers/stdio_console.c
index 5e44adb..e4bfcfe 100644
--- a/arch/um/drivers/stdio_console.c
+++ b/arch/um/drivers/stdio_console.c
@@ -108,6 +108,7 @@
return line_open(vts, tty);
}
+/* Set in an initcall, checked in an exitcall */
static int con_init_done = 0;
static const struct tty_operations console_ops = {
diff --git a/arch/um/kernel/exitcode.c b/arch/um/kernel/exitcode.c
index d21ebad..8b7f2cd 100644
--- a/arch/um/kernel/exitcode.c
+++ b/arch/um/kernel/exitcode.c
@@ -16,9 +16,13 @@
static int read_proc_exitcode(char *page, char **start, off_t off,
int count, int *eof, void *data)
{
- int len;
+ int len, val;
- len = sprintf(page, "%d\n", uml_exitcode);
+ /* Save uml_exitcode in a local so that we don't need to guarantee
+ * that sprintf accesses it atomically.
+ */
+ val = uml_exitcode;
+ len = sprintf(page, "%d\n", val);
len -= off;
if(len <= off+count) *eof = 1;
*start = page + off;