From: Michal Hocko <[email protected]> devm_memremap_pages is initializing struct pages in for_each_device_pfn and that can take quite some time. We have even seen a soft lockup trigerring on a non preemptive kernel [ 125.583233] NMI watchdog: BUG: soft lockup - CPU#61 stuck for 22s! [kworker/u641:11:1808] [...] [ 125.583467] RIP: 0010:[<ffffffff8118b6b7>] [<ffffffff8118b6b7>] devm_memremap_pages+0x327/0x430 [...] [ 125.583488] Call Trace: [ 125.583496] [<ffffffffa016550d>] pmem_attach_disk+0x2fd/0x3f0 [nd_pmem] [ 125.583528] [<ffffffffa14ae984>] nvdimm_bus_probe+0x64/0x110 [libnvdimm] [ 125.583536] [<ffffffff8146b257>] driver_probe_device+0x1f7/0x420 [ 125.583540] [<ffffffff81469212>] bus_for_each_drv+0x52/0x80 [ 125.583543] [<ffffffff8146af40>] __device_attach+0xb0/0x130 [ 125.583546] [<ffffffff8146a367>] bus_probe_device+0x87/0xa0 [ 125.583548] [<ffffffff814682fc>] device_add+0x3fc/0x5f0 [ 125.583553] [<ffffffffa14adffe>] nd_async_device_register+0xe/0x40 [libnvdimm] [ 125.583556] [<ffffffff8109e413>] async_run_entry_fn+0x43/0x150 [ 125.583561] [<ffffffff81095b8e>] process_one_work+0x14e/0x410 [ 125.583563] [<ffffffff810963f6>] worker_thread+0x116/0x490 [ 125.583565] [<ffffffff8109b8c7>] kthread+0xc7/0xe0 [ 125.583569] [<ffffffff8160a57f>] ret_from_fork+0x3f/0x70
fix this by adding cond_resched every 1024 pages. Reported-by: Johannes Thumshirn <[email protected]> Signed-off-by: Michal Hocko <[email protected]> --- kernel/memremap.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/memremap.c b/kernel/memremap.c index 6bcbfbf1a8fd..403ab9cdb949 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -350,7 +350,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, pgprot_t pgprot = PAGE_KERNEL; struct dev_pagemap *pgmap; struct page_map *page_map; - int error, nid, is_ram; + int error, nid, is_ram, i = 0; align_start = res->start & ~(SECTION_SIZE - 1); align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE) @@ -448,6 +448,8 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, list_del(&page->lru); page->pgmap = pgmap; percpu_ref_get(ref); + if (!(++i % 1024)) + cond_resched(); } devres_add(dev, page_map); return __va(res->start); -- 2.14.1
