From: Michal Hocko mhocko@suse.com Subject: memory_hotplug: cond_resched in __remove_pages

We have received a bug report that unbinding a large pmem (>1TB) can result in a soft lockup:

[ 380.339203] NMI watchdog: BUG: soft lockup - CPU#9 stuck for 23s! [ndctl:4365] [...] [ 380.339316] Supported: Yes [ 380.339318] CPU: 9 PID: 4365 Comm: ndctl Not tainted 4.12.14-94.40-default #1 SLE12-SP4 [ 380.339318] Hardware name: Intel Corporation S2600WFD/S2600WFD, BIOS SE5C620.86B.01.00.0833.051120182255 05/11/2018 [ 380.339319] task: ffff9cce7d4410c0 task.stack: ffffbe9eb1bc4000 [ 380.339325] RIP: 0010:__put_page+0x62/0x80 [ 380.339326] RSP: 0018:ffffbe9eb1bc7d30 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10 [ 380.339327] RAX: 000040540081c0d3 RBX: ffffeb8f03557200 RCX: 000063af40000000 [ 380.339328] RDX: 0000000000000002 RSI: ffff9cce75bff498 RDI: ffff9e4a76072ff8 [ 380.339329] RBP: 0000000a43557200 R08: 0000000000000000 R09: ffffbe9eb1bc7bb0 [ 380.339329] R10: ffffbe9eb1bc7d08 R11: 0000000000000000 R12: ffff9e194a22a0e0 [ 380.339330] R13: ffff9cce7062fc10 R14: ffff9e194a22a0a0 R15: ffff9cce6559c0e0 [ 380.339331] FS: 00007fd132368880(0000) GS:ffff9cce7ea40000(0000) knlGS:0000000000000000 [ 380.339332] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 380.339332] CR2: 00000000020820a0 CR3: 000000017ef7a003 CR4: 00000000007606e0 [ 380.339333] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 380.339334] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 380.339334] PKRU: 55555554 [ 380.339334] Call Trace: [ 380.339338] devm_memremap_pages_release+0x152/0x260 [ 380.339342] release_nodes+0x18d/0x1d0 [ 380.339347] device_release_driver_internal+0x160/0x210 [ 380.339350] unbind_store+0xb3/0xe0 [ 380.339355] kernfs_fop_write+0x102/0x180 [ 380.339358] __vfs_write+0x26/0x150 [ 380.339363] ? security_file_permission+0x3c/0xc0 [ 380.339364] vfs_write+0xad/0x1a0 [ 380.339366] SyS_write+0x42/0x90 [ 380.339370] do_syscall_64+0x74/0x150 [ 380.339375] entry_SYSCALL_64_after_hwframe+0x3d/0xa2 [ 380.339377] 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 ---

mm/memory_hotplug.c | 1 + 1 file changed, 1 insertion(+)

--- a/mm/memory_hotplug.c~memory_hotplug-cond_resched-in-__remove_pages +++ a/mm/memory_hotplug.c @@ -586,6 +586,7 @@ 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; _