diff options
Diffstat (limited to 'ipc/ipcns_notifier.c')
-rw-r--r-- | ipc/ipcns_notifier.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/ipc/ipcns_notifier.c b/ipc/ipcns_notifier.c new file mode 100644 index 0000000..0786af6 --- /dev/null +++ b/ipc/ipcns_notifier.c @@ -0,0 +1,71 @@ +/* + * linux/ipc/ipcns_notifier.c + * Copyright (C) 2007 BULL SA. Nadia Derbey + * + * Notification mechanism for ipc namespaces: + * The callback routine registered in the memory chain invokes the ipcns + * notifier chain with the IPCNS_MEMCHANGED event. + * Each callback routine registered in the ipcns namespace recomputes msgmni + * for the owning namespace. + */ + +#include <linux/msg.h> +#include <linux/rcupdate.h> +#include <linux/notifier.h> +#include <linux/nsproxy.h> +#include <linux/ipc_namespace.h> + +#include "util.h" + + + +static BLOCKING_NOTIFIER_HEAD(ipcns_chain); + + +static int ipcns_callback(struct notifier_block *self, + unsigned long action, void *arg) +{ + struct ipc_namespace *ns; + + switch (action) { + case IPCNS_MEMCHANGED: /* amount of lowmem has changed */ + /* + * It's time to recompute msgmni + */ + ns = container_of(self, struct ipc_namespace, ipcns_nb); + /* + * No need to get a reference on the ns: the 1st job of + * free_ipc_ns() is to unregister the callback routine. + * blocking_notifier_chain_unregister takes the wr lock to do + * it. + * When this callback routine is called the rd lock is held by + * blocking_notifier_call_chain. + * So the ipc ns cannot be freed while we are here. + */ + recompute_msgmni(ns); + break; + default: + break; + } + + return NOTIFY_OK; +} + +int register_ipcns_notifier(struct ipc_namespace *ns) +{ + memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb)); + ns->ipcns_nb.notifier_call = ipcns_callback; + ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI; + return blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb); +} + +int unregister_ipcns_notifier(struct ipc_namespace *ns) +{ + return blocking_notifier_chain_unregister(&ipcns_chain, + &ns->ipcns_nb); +} + +int ipcns_notify(unsigned long val) +{ + return blocking_notifier_call_chain(&ipcns_chain, val, NULL); +} |