Re: [linux-pm] [PATCH] hibernation should work ok with memory hotplug

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Thu, 6 Nov 2008 11:07:09 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> Okay. then we can add "kernel thread for calling add/remove memory" and say
> "PLEASE WAIT UNTIL HIBERNATION IS READY".
> 
> I can try that by myself but doesn't have suitable machine....
> I think I can show you pseudo code in hours. please wait a bit.
> 

How about this one ? as a start step ?
I have no test environment. So please take this as a sample.
-Kame
=

Now, MEMORY_HOTPLUG and HIBERNATION is mutually exclusive in Kconfig.
That's because
	- memory hotplug changes pgdat/zone/memmap range.
	- hibernation countes # of memory based on pgdate/zone/memmap.

This patch adds rwsemaphore for making them not to run at the same time.

IIUC, add_memory() is called from following places.
    - probe interface
    - acpi handler
It seems both can sleep. (acpi handler uses sleepable memory allocator etc...)

online/offline handlers also sleeps.

Anyway, the most difficult thing is how to test this.


Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

 mm/Kconfig          |    2 -
 mm/memory_hotplug.c |   61 +++++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 54 insertions(+), 9 deletions(-)

Index: linux-2.6.27.4/mm/memory_hotplug.c
===================================================================
--- linux-2.6.27.4.orig/mm/memory_hotplug.c
+++ linux-2.6.27.4/mm/memory_hotplug.c
@@ -31,6 +31,13 @@
 
 #include "internal.h"
 
+struct rw_semaphore memhp_mutex;
+
+static int init_memhp_mutex(void)
+{
+	init_rwsem(&memhp_mutex);
+}
+
 /* add this memory to iomem resource */
 static struct resource *register_memory_resource(u64 start, u64 size)
 {
@@ -381,6 +388,7 @@ int online_pages(unsigned long pfn, unsi
 	int ret;
 	struct memory_notify arg;
 
+	down_read(&memhp_mutex);
 	arg.start_pfn = pfn;
 	arg.nr_pages = nr_pages;
 	arg.status_change_nid = -1;
@@ -392,6 +400,7 @@ int online_pages(unsigned long pfn, unsi
 	ret = memory_notify(MEM_GOING_ONLINE, &arg);
 	ret = notifier_to_errno(ret);
 	if (ret) {
+		up_read(&memhp_mutex);
 		memory_notify(MEM_CANCEL_ONLINE, &arg);
 		return ret;
 	}
@@ -415,6 +424,7 @@ int online_pages(unsigned long pfn, unsi
 		printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
 			nr_pages, pfn);
 		memory_notify(MEM_CANCEL_ONLINE, &arg);
+		up_read(&memhp_mutex);
 		return ret;
 	}
 
@@ -436,7 +446,7 @@ int online_pages(unsigned long pfn, unsi
 
 	if (onlined_pages)
 		memory_notify(MEM_ONLINE, &arg);
-
+	up_read(&memhp_mutex);
 	return 0;
 }
 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
@@ -477,14 +487,18 @@ int add_memory(int nid, u64 start, u64 s
 	struct resource *res;
 	int ret;
 
+	down_read(&memhp_mutex);
 	res = register_memory_resource(start, size);
-	if (!res)
+	if (!res) {
+		up_read(&memhp_mutex);
 		return -EEXIST;
-
+	}
 	if (!node_online(nid)) {
 		pgdat = hotadd_new_pgdat(nid, start);
-		if (!pgdat)
+		if (!pgdat) {
+			up_read(&memhp_mutex);
 			return -ENOMEM;
+		}
 		new_pgdat = 1;
 	}
 
@@ -508,7 +522,7 @@ int add_memory(int nid, u64 start, u64 s
 		 */
 		BUG_ON(ret);
 	}
-
+	up_read(&memhp_mutex);
 	return ret;
 error:
 	/* rollback pgdat allocation and others */
@@ -517,10 +531,12 @@ error:
 	if (res)
 		release_memory_resource(res);
 
+	up_read(&memhp_mutex);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(add_memory);
 
+
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
  * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
@@ -750,20 +766,23 @@ int offline_pages(unsigned long start_pf
 		return -EINVAL;
 	if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
 		return -EINVAL;
+
 	/* This makes hotplug much easier...and readable.
 	   we assume this for now. .*/
 	if (!test_pages_in_a_zone(start_pfn, end_pfn))
 		return -EINVAL;
 
+	down_read(&memhp_mutex);
 	zone = page_zone(pfn_to_page(start_pfn));
 	node = zone_to_nid(zone);
 	nr_pages = end_pfn - start_pfn;
 
 	/* set above range as isolated */
 	ret = start_isolate_page_range(start_pfn, end_pfn);
-	if (ret)
+	if (ret) {
+		up_read(&memhp_mutex);
 		return ret;
-
+	}
 	arg.start_pfn = start_pfn;
 	arg.nr_pages = nr_pages;
 	arg.status_change_nid = -1;
@@ -838,6 +857,7 @@ repeat:
 	writeback_set_ratelimit();
 
 	memory_notify(MEM_OFFLINE, &arg);
+	up_read(&memhp_mutex);
 	return 0;
 
 failed_removal:
@@ -846,7 +866,7 @@ failed_removal:
 	memory_notify(MEM_CANCEL_OFFLINE, &arg);
 	/* pushback to free area */
 	undo_isolate_page_range(start_pfn, end_pfn);
-
+	up_read(&memhp_mutex);
 	return ret;
 }
 #else
@@ -856,3 +876,34 @@ int remove_memory(u64 start, u64 size)
 }
 EXPORT_SYMBOL_GPL(remove_memory);
 #endif /* CONFIG_MEMORY_HOTREMOVE */
+
+
+#ifdef CONFIG_HIBERNATION
+
+int memhp_hibenation_callback(struct notifier_block *self,
+			      unsigned long action,
+			      void *arg)
+{
+	int ret;
+
+	switch(action) {
+	case PM_HIBERNATION_PREPARE:
+		down_write(&memhp_mutex);
+		break;
+	case PM_POST_HIBERNATION:
+		up_write(&memhp_mutex);
+		break;
+	case PM_RESTORE_PREPARE:
+		down_write(&memhp_mutex);
+		break;
+	case PM_POST_RESTORE:
+		up_write(&memhp_mutex);
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+#endif
+
+
Index: linux-2.6.27.4/mm/Kconfig
===================================================================
--- linux-2.6.27.4.orig/mm/Kconfig
+++ linux-2.6.27.4/mm/Kconfig
@@ -128,12 +128,9 @@ config SPARSEMEM_VMEMMAP
 config MEMORY_HOTPLUG
 	bool "Allow for memory hot-add"
 	depends on SPARSEMEM || X86_64_ACPI_NUMA
-	depends on HOTPLUG && !HIBERNATION && ARCH_ENABLE_MEMORY_HOTPLUG
+	depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 	depends on (IA64 || X86 || PPC64 || SUPERH || S390)
 
-comment "Memory hotplug is currently incompatible with Software Suspend"
-	depends on SPARSEMEM && HOTPLUG && HIBERNATION
-
 config MEMORY_HOTPLUG_SPARSE
 	def_bool y
 	depends on SPARSEMEM && MEMORY_HOTPLUG

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