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dkim=pass header.d=amd.com header.s=selector1 header.b=T3il3wrD; dmarc=pass (policy=quarantine) header.from=amd.com; spf=pass (imf07.hostedemail.com: domain of Lang.Yu@amd.com designates 40.107.220.88 as permitted sender) smtp.mailfrom=Lang.Yu@amd.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 5F42C10000B4 X-HE-Tag: 1637722692-586935 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 08, 2021 at 10:00:29PM +0800, Lang Yu wrote: Ping. > When using devm_request_free_mem_region() and devm_memremap_pages() > to add ZONE_DEVICE memory, if requested free mem region's end pfn > were huge(e.g., 0x400000000), the node_end_pfn() will be also huge > (see move_pfn_range_to_zone()). Thus it creates a huge hole between > node_start_pfn() and node_end_pfn(). > > We found on some AMD APUs, amdkfd requested such a free mem region > and created a huge hole. In such a case, following code snippet was > just doing busy test_bit() looping on the huge hole. > > for (pfn = start_pfn; pfn < end_pfn; pfn++) { > struct page *page = pfn_to_online_page(pfn); > if (!page) > continue; > ... > } > > So we got a soft lockup: > > watchdog: BUG: soft lockup - CPU#6 stuck for 26s! [bash:1221] > CPU: 6 PID: 1221 Comm: bash Not tainted 5.15.0-custom #1 > RIP: 0010:pfn_to_online_page+0x5/0xd0 > Call Trace: > ? kmemleak_scan+0x16a/0x440 > kmemleak_write+0x306/0x3a0 > ? common_file_perm+0x72/0x170 > full_proxy_write+0x5c/0x90 > vfs_write+0xb9/0x260 > ksys_write+0x67/0xe0 > __x64_sys_write+0x1a/0x20 > do_syscall_64+0x3b/0xc0 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > I did some tests with the patch. > > (1) amdgpu module unloaded > > before the patch: > > real 0m0.976s > user 0m0.000s > sys 0m0.968s > > after the patch: > > real 0m0.981s > user 0m0.000s > sys 0m0.973s > > (2) amdgpu module loaded > > before the patch: > > real 0m35.365s > user 0m0.000s > sys 0m35.354s > > after the patch: > > real 0m1.049s > user 0m0.000s > sys 0m1.042s > > v2: > - Only scan pages belonging to the zone.(David Hildenbrand) > - Use __maybe_unused to make compilers happy. > > Signed-off-by: Lang Yu > --- > mm/kmemleak.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index b57383c17cf6..adbe5aa01184 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -1403,7 +1403,8 @@ static void kmemleak_scan(void) > { > unsigned long flags; > struct kmemleak_object *object; > - int i; > + struct zone *zone; > + int __maybe_unused i; > int new_leaks = 0; > > jiffies_last_scan = jiffies; > @@ -1443,9 +1444,9 @@ static void kmemleak_scan(void) > * Struct page scanning for each node. > */ > get_online_mems(); > - for_each_online_node(i) { > - unsigned long start_pfn = node_start_pfn(i); > - unsigned long end_pfn = node_end_pfn(i); > + for_each_populated_zone(zone) { > + unsigned long start_pfn = zone->zone_start_pfn; > + unsigned long end_pfn = zone_end_pfn(zone); > unsigned long pfn; > > for (pfn = start_pfn; pfn < end_pfn; pfn++) { > @@ -1454,8 +1455,8 @@ static void kmemleak_scan(void) > if (!page) > continue; > > - /* only scan pages belonging to this node */ > - if (page_to_nid(page) != i) > + /* only scan pages belonging to this zone */ > + if (page_zone(page) != zone) > continue; > /* only scan if page is in use */ > if (page_count(page) == 0) > -- > 2.25.1 >