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authorNadia Derbey <Nadia.Derbey@bull.net>2008-07-25 01:48:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-25 10:53:42 -0700
commit9eefe520c814f6f62c5d36a2ddcd3fb99dfdb30e (patch)
tree064ce99674f144b681f8d365d1e20d99c8078d0c /include/linux/ipc_namespace.h
parentf1a43f93f0f3bab418800eaccb9e2e3b5427e173 (diff)
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ipc: do not use a negative value to re-enable msgmni automatic recomputing
This patch proposes an alternative to the "magical positive-versus-negative number trick" Andrew complained about last week in http://lkml.org/lkml/2008/6/24/418. This had been introduced with the patches that scale msgmni to the amount of lowmem. With these patches, msgmni has a registered notification routine that recomputes msgmni value upon memory add/remove or ipc namespace creation/ removal. When msgmni is changed from user space (i.e. value written to the proc file), that notification routine is unregistered, and the way to make it registered back is to write a negative value into the proc file. This is the "magical positive-versus-negative number trick". To fix this, a new proc file is introduced: /proc/sys/kernel/auto_msgmni. This file acts as ON/OFF for msgmni automatic recomputing. With this patch, the process is the following: 1) kernel boots in "automatic recomputing mode" /proc/sys/kernel/msgmni contains the value that has been computed (depends on lowmem) /proc/sys/kernel/automatic_msgmni contains "1" 2) echo <val> > /proc/sys/kernel/msgmni . sets msg_ctlmni to <val> . de-activates automatic recomputing (i.e. if, say, some memory is added msgmni won't be recomputed anymore) . /proc/sys/kernel/automatic_msgmni now contains "0" 3) echo "0" > /proc/sys/kernel/automatic_msgmni . de-activates msgmni automatic recomputing this has the same effect as 2) except that msg_ctlmni's value stays blocked at its current value) 3) echo "1" > /proc/sys/kernel/automatic_msgmni . recomputes msgmni's value based on the current available memory size and number of ipc namespaces . re-activates automatic recomputing for msgmni. Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net> Cc: Solofo Ramangalahy <Solofo.Ramangalahy@bull.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/ipc_namespace.h')
-rw-r--r--include/linux/ipc_namespace.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index ea6c18a8b0d..ea330f9e710 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -36,6 +36,7 @@ struct ipc_namespace {
int msg_ctlmni;
atomic_t msg_bytes;
atomic_t msg_hdrs;
+ int auto_msgmni;
size_t shm_ctlmax;
size_t shm_ctlall;
@@ -53,7 +54,7 @@ extern atomic_t nr_ipc_ns;
extern int register_ipcns_notifier(struct ipc_namespace *);
extern int cond_register_ipcns_notifier(struct ipc_namespace *);
-extern int unregister_ipcns_notifier(struct ipc_namespace *);
+extern void unregister_ipcns_notifier(struct ipc_namespace *);
extern int ipcns_notify(unsigned long);
#else /* CONFIG_SYSVIPC */