4.18-stable review patch. If anyone has any objections, please let me know.
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From: Michal Hocko mhocko@suse.com
commit dd33ad7b251f900481701b2a82d25de583867708 upstream.
We have received a bug report that unbinding a large pmem (>1TB) can result in a soft lockup:
NMI watchdog: BUG: soft lockup - CPU#9 stuck for 23s! [ndctl:4365] [...] Supported: Yes CPU: 9 PID: 4365 Comm: ndctl Not tainted 4.12.14-94.40-default #1 SLE12-SP4 Hardware name: Intel Corporation S2600WFD/S2600WFD, BIOS SE5C620.86B.01.00.0833.051120182255 05/11/2018 task: ffff9cce7d4410c0 task.stack: ffffbe9eb1bc4000 RIP: 0010:__put_page+0x62/0x80 Call Trace: devm_memremap_pages_release+0x152/0x260 release_nodes+0x18d/0x1d0 device_release_driver_internal+0x160/0x210 unbind_store+0xb3/0xe0 kernfs_fop_write+0x102/0x180 __vfs_write+0x26/0x150 vfs_write+0xad/0x1a0 SyS_write+0x42/0x90 do_syscall_64+0x74/0x150 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x7fd13166b3d0
It has been reported on an older (4.12) kernel but the current upstream code doesn't cond_resched in the hot remove code at all and the given range to remove might be really large. Fix the issue by calling cond_resched once per memory section.
Link: http://lkml.kernel.org/r/20181031125840.23982-1-mhocko@kernel.org Signed-off-by: Michal Hocko mhocko@suse.com Acked-by: Johannes Thumshirn jthumshirn@suse.de Cc: Dan Williams dan.j.williams@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/memory_hotplug.c | 1 + 1 file changed, 1 insertion(+)
--- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -587,6 +587,7 @@ int __remove_pages(struct zone *zone, un for (i = 0; i < sections_to_remove; i++) { unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
+ cond_resched(); ret = __remove_section(zone, __pfn_to_section(pfn), map_offset, altmap); map_offset = 0;