sysctl: add support for poll()
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>
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 9a1ec10..703cfa3 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -931,6 +931,7 @@
#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 @@
* 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 *child;
struct ctl_table *parent; /* Automatically set */
proc_handler *proc_handler; /* Callback for text formatting */
+ struct ctl_table_poll *poll;
void *extra1;
void *extra2;
};