At 07/20/2012 07:18 PM, Vasilis Liaskovitis Wrote: > hot-remove initiated by acpi_memhotplug driver tries to offline pages and then > remove section/sysfs files in remove_memory(). remove_memory() will only proceed > if is_memblk_offline() returns true, i.e. only if the corresponding memblock > is in MEM_OFFLINE state. However, the memblock state is currently only updated > if the offlining has been initiated from the sysfs interface (echo offline > > /sys/devices/system/memory/memoryXX/state). The acpi hot-remove codepath does > not use the sysfs interface but directly calls offline_pages. So remove_memory() > will always fail, even if offline_pages has succeeded. Thank you for pointing this problem. > > This patch solves this by registering a memblock_state notifier function in the > memory_notify chain. This will change state of memblocks independently of sysfs > usage. I think this patch does not solve this problem. > > The patch is based on work-in-progress patches for memory hot-remove, see: > http://lwn.net/Articles/507244/ > > Signed-off-by: Vasilis Liaskovitis <vasilis.liaskovitis@xxxxxxxxxxxxxxxx> > --- > drivers/base/memory.c | 37 +++++++++++++++++++++++++++++++++++++ > 1 files changed, 37 insertions(+), 0 deletions(-) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 8981568..4095f3f 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -706,6 +706,42 @@ int unregister_memory_section(struct mem_section *section) > return remove_memory_block(0, section, 0); > } > > +static int memblock_state_notifier_nb(struct notifier_block *nb, unsigned long > + val, void *v) > +{ > + struct memory_notify *arg = (struct memory_notify *)v; > + struct memory_block *mem = NULL; > + struct mem_section *ms; > + unsigned long section_nr; > + > + section_nr = pfn_to_section_nr(arg->start_pfn); > + ms = __nr_to_section(section_nr); > + mem = find_memory_block(ms); > + if (!mem) > + goto out; we may offline more than one memory block. > + > + switch (val) { > + case MEM_GOING_OFFLINE: > + case MEM_OFFLINE: > + case MEM_GOING_ONLINE: > + case MEM_ONLINE: > + case MEM_CANCEL_ONLINE: > + case MEM_CANCEL_OFFLINE: > + mem->state = val; mem->state is protected by the lock mem->state_mutex, so if you want to update the state, you must lock mem->state_mutex. But you cannot lock it here, because it may cause deadlock: acpi_memhotplug sysfs interface =============================================================================== memory_block_change_state() lock mem->state_mutex memory_block_action() offline_pages() lock_memory_hotplug() offline_memory() lock_memory_hotplug() // block memory_notify() memblock_state_notifier_nb() =============================================================================== I'm writing another patch to fix it. Thanks Wen Congyang > + break; > + default: > + printk(KERN_WARNING "invalid memblock state\n"); > + break; > + } > +out: > + return NOTIFY_OK; > +} > + > +static struct notifier_block memblock_state_nb = { > + .notifier_call = memblock_state_notifier_nb, > + .priority = 0 > +}; > + > /* > * Initialize the sysfs support for memory devices... > */ > @@ -724,6 +760,7 @@ int __init memory_dev_init(void) > block_sz = get_memory_block_size(); > sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE; > > + register_memory_notifier(&memblock_state_nb); > /* > * Create entries for memory sections that were found > * during boot and have been initialized -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>