linux/arch/um/kernel/exitcode.c
Jeff Dike 730760e90a [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>
2006-09-29 09:18:04 -07:00

78 lines
1.8 KiB
C

/*
* Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
* Licensed under the GPL
*/
#include "linux/init.h"
#include "linux/ctype.h"
#include "linux/proc_fs.h"
#include "asm/uaccess.h"
/* If read and write race, the read will still atomically read a valid
* value.
*/
int uml_exitcode = 0;
static int read_proc_exitcode(char *page, char **start, off_t off,
int count, int *eof, void *data)
{
int len, val;
/* 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;
if(len > count) len = count;
if(len < 0) len = 0;
return(len);
}
static int write_proc_exitcode(struct file *file, const char __user *buffer,
unsigned long count, void *data)
{
char *end, buf[sizeof("nnnnn\0")];
int tmp;
if(copy_from_user(buf, buffer, count))
return(-EFAULT);
tmp = simple_strtol(buf, &end, 0);
if((*end != '\0') && !isspace(*end))
return(-EINVAL);
uml_exitcode = tmp;
return(count);
}
static int make_proc_exitcode(void)
{
struct proc_dir_entry *ent;
ent = create_proc_entry("exitcode", 0600, &proc_root);
if(ent == NULL){
printk(KERN_WARNING "make_proc_exitcode : Failed to register "
"/proc/exitcode\n");
return(0);
}
ent->read_proc = read_proc_exitcode;
ent->write_proc = write_proc_exitcode;
return(0);
}
__initcall(make_proc_exitcode);
/*
* Overrides for Emacs so that we follow Linus's tabbing style.
* Emacs will notice this stuff at the end of the file and automatically
* adjust the settings for this buffer only. This must remain at the end
* of the file.
* ---------------------------------------------------------------------------
* Local variables:
* c-file-style: "linux"
* End:
*/