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730760e90a
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>
78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
/*
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* Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
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* Licensed under the GPL
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*/
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#include "linux/init.h"
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#include "linux/ctype.h"
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#include "linux/proc_fs.h"
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#include "asm/uaccess.h"
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/* If read and write race, the read will still atomically read a valid
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* value.
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*/
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int uml_exitcode = 0;
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static int read_proc_exitcode(char *page, char **start, off_t off,
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int count, int *eof, void *data)
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{
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int len, val;
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/* Save uml_exitcode in a local so that we don't need to guarantee
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* that sprintf accesses it atomically.
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*/
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val = uml_exitcode;
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len = sprintf(page, "%d\n", val);
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len -= off;
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if(len <= off+count) *eof = 1;
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*start = page + off;
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if(len > count) len = count;
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if(len < 0) len = 0;
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return(len);
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}
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static int write_proc_exitcode(struct file *file, const char __user *buffer,
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unsigned long count, void *data)
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{
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char *end, buf[sizeof("nnnnn\0")];
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int tmp;
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if(copy_from_user(buf, buffer, count))
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return(-EFAULT);
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tmp = simple_strtol(buf, &end, 0);
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if((*end != '\0') && !isspace(*end))
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return(-EINVAL);
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uml_exitcode = tmp;
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return(count);
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}
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static int make_proc_exitcode(void)
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{
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struct proc_dir_entry *ent;
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ent = create_proc_entry("exitcode", 0600, &proc_root);
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if(ent == NULL){
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printk(KERN_WARNING "make_proc_exitcode : Failed to register "
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"/proc/exitcode\n");
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return(0);
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}
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ent->read_proc = read_proc_exitcode;
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ent->write_proc = write_proc_exitcode;
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return(0);
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}
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__initcall(make_proc_exitcode);
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/*
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* Overrides for Emacs so that we follow Linus's tabbing style.
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* Emacs will notice this stuff at the end of the file and automatically
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* adjust the settings for this buffer only. This must remain at the end
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* of the file.
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* ---------------------------------------------------------------------------
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* Local variables:
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* c-file-style: "linux"
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* End:
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*/
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