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ipc: re-enable msgmni automatic recomputing msgmni if set to negative

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The enhancement as asked for by Yasunori: if msgmni is set to a negative
value, register it back into the ipcns notifier chain.

A new interface has been added to the notification mechanism:
notifier_chain_cond_register() registers a notifier block only if not already
registered.  With that new interface we avoid taking care of the states
changes in procfs.

Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Pierre Peiffer <pierre.peiffer@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nadia Derbey
2008-04-29 01:00:45 -07:00
committed by Linus Torvalds
parent 91cfb2b4b5
commit 6546bc4279
5 changed files with 87 additions and 10 deletions
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38
kernel/notifier.c
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@@ -31,6 +31,21 @@ static int notifier_chain_register(struct notifier_block **nl,
return 0;
}
static int notifier_chain_cond_register(struct notifier_block **nl,
struct notifier_block *n)
{
while ((*nl) != NULL) {
if ((*nl) == n)
return 0;
if (n->priority > (*nl)->priority)
break;
nl = &((*nl)->next);
}
n->next = *nl;
rcu_assign_pointer(*nl, n);
return 0;
}
static int notifier_chain_unregister(struct notifier_block **nl,
struct notifier_block *n)
{
@@ -204,6 +219,29 @@ int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
}
EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
/**
* blocking_notifier_chain_cond_register - Cond add notifier to a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain
* @n: New entry in notifier chain
*
* Adds a notifier to a blocking notifier chain, only if not already
* present in the chain.
* Must be called in process context.
*
* Currently always returns zero.
*/
int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh,
struct notifier_block *n)
{
int ret;
down_write(&nh->rwsem);
ret = notifier_chain_cond_register(&nh->head, n);
up_write(&nh->rwsem);
return ret;
}
EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register);
/**
* blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain