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

KAMEZAWA Hiroyuki
2008-11-06T03:12:12Z

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