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>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index 58459509b14c..d06c091e0345 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1286,6 +1286,7 @@ SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)
                 memset(u->nodename + len, 0, sizeof(u->nodename) - len);
                 errno = 0;
         }
+        uts_proc_notify(UTS_PROC_HOSTNAME);
         up_write(&uts_sem);
         return errno;
 }
@@ -1336,6 +1337,7 @@ SYSCALL_DEFINE2(setdomainname, char __user *, name, int, len)
                 memset(u->domainname + len, 0, sizeof(u->domainname) - len);
                 errno = 0;
         }
+        uts_proc_notify(UTS_PROC_DOMAINNAME);
         up_write(&uts_sem);
         return errno;
 }