ipcns_notifier.c

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    1 /*
    2  * linux/ipc/ipcns_notifier.c
    3  * Copyright (C) 2007 BULL SA. Nadia Derbey
    4  *
    5  * Notification mechanism for ipc namespaces:
    6  * The callback routine registered in the memory chain invokes the ipcns
    7  * notifier chain with the IPCNS_MEMCHANGED event.
    8  * Each callback routine registered in the ipcns namespace recomputes msgmni
    9  * for the owning namespace.
   10  */
   11 
   12 #include <linux/msg.h>
   13 #include <linux/rcupdate.h>
   14 #include <linux/notifier.h>
   15 #include <linux/nsproxy.h>
   16 #include <linux/ipc_namespace.h>
   17 
   18 #include "util.h"
   19 
   20 
   21 
   22 static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
   23 
   24 
   25 static int ipcns_callback(struct notifier_block *self,
   26                                 unsigned long action, void *arg)
   27 {
   28         struct ipc_namespace *ns;
   29 
   30         switch (action) {
   31         case IPCNS_MEMCHANGED:   /* amount of lowmem has changed */
   32         case IPCNS_CREATED:
   33         case IPCNS_REMOVED:
   34                 /*
   35                  * It's time to recompute msgmni
   36                  */
   37                 ns = container_of(self, struct ipc_namespace, ipcns_nb);
   38                 /*
   39                  * No need to get a reference on the ns: the 1st job of
   40                  * free_ipc_ns() is to unregister the callback routine.
   41                  * blocking_notifier_chain_unregister takes the wr lock to do
   42                  * it.
   43                  * When this callback routine is called the rd lock is held by
   44                  * blocking_notifier_call_chain.
   45                  * So the ipc ns cannot be freed while we are here.
   46                  */
   47                 recompute_msgmni(ns);
   48                 break;
   49         default:
   50                 break;
   51         }
   52 
   53         return NOTIFY_OK;
   54 }
   55 
   56 int register_ipcns_notifier(struct ipc_namespace *ns)
   57 {
   58         int rc;
   59 
   60         memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
   61         ns->ipcns_nb.notifier_call = ipcns_callback;
   62         ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
   63         rc = blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
   64         if (!rc)
   65                 ns->auto_msgmni = 1;
   66         return rc;
   67 }
   68 
   69 int cond_register_ipcns_notifier(struct ipc_namespace *ns)
   70 {
   71         int rc;
   72 
   73         memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
   74         ns->ipcns_nb.notifier_call = ipcns_callback;
   75         ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
   76         rc = blocking_notifier_chain_cond_register(&ipcns_chain,
   77                                                         &ns->ipcns_nb);
   78         if (!rc)
   79                 ns->auto_msgmni = 1;
   80         return rc;
   81 }
   82 
   83 void unregister_ipcns_notifier(struct ipc_namespace *ns)
   84 {
   85         blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb);
   86         ns->auto_msgmni = 0;
   87 }
   88 
   89 int ipcns_notify(unsigned long val)
   90 {
   91         return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
   92 }

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FreeBSD/Linux Kernel Cross Reference sys/ipc/ipcns_notifier.c

FreeBSD/Linux Kernel Cross Reference
sys/ipc/ipcns_notifier.c