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sysctl: add support for poll()

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Adding support for poll() in sysctl fs allows userspace to receive
notifications of changes in sysctl entries.  This adds a infrastructure to
allow files in sysctl fs to be pollable and implements it for hostname and
domainname.

[akpm@linux-foundation.org: s/declare/define/ for definitions]
Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Greg KH <gregkh@suse.de>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lucas De Marchi 2011-11-02 13:39:22 -07:00 • committed by Linus Torvalds
parent 088024b1de
commit f1ecf06854
5 changed files with 108 additions and 0 deletions
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22
include/linux/sysctl.h
View file

@ -931,6 +931,7 @@ enum
#ifdef __KERNEL__
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <linux/wait.h>
/* For the /proc/sys support */
struct ctl_table;
@ -1011,6 +1012,26 @@ extern int proc_do_large_bitmap(struct ctl_table *, int,
* cover common cases.
*/
/* Support for userspace poll() to watch for changes */
struct ctl_table_poll {
atomic_t event;
wait_queue_head_t wait;
};
static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
{
return (void *)(unsigned long)atomic_read(&poll->event);
}
void proc_sys_poll_notify(struct ctl_table_poll *poll);
#define __CTL_TABLE_POLL_INITIALIZER(name) { \
.event = ATOMIC_INIT(0), \
.wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
#define DEFINE_CTL_TABLE_POLL(name) \
struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
/* A sysctl table is an array of struct ctl_table: */
struct ctl_table
{
@ -1021,6 +1042,7 @@ struct ctl_table
struct ctl_table *child;
struct ctl_table *parent; /* Automatically set */
proc_handler *proc_handler; /* Callback for text formatting */
struct ctl_table_poll *poll;
void *extra1;
void *extra2;
};