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

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

On Thu, 06 Nov 2008 12:28:30 +0900
Yasunori Goto <y-goto@jp.fujitsu.com> wrote:

> 
> Hmm.
> 
> I think simple mutex is enough. read/write lock is not necessary.
> Memory hotplug event is very rare, and there is no requirement of
> parallel execution.
> 

OK, change it to mutex and start new thread.

Thanks,
-Kame

> 
> > 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
> > 
> 
> -- 
> Yasunori Goto 
> 
> 
> 

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