/* * 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 */ case IPCNS_CREATED: case IPCNS_REMOVED: /* * 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 cond_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_cond_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); }