On Fri 25-10-19 13:55:13, Robert Stupp wrote: > On Fri, 2019-10-25 at 13:46 +0200, Michal Hocko wrote: > > On Fri 25-10-19 13:02:23, Robert Stupp wrote: > > > On Fri, 2019-10-25 at 11:21 +0200, Michal Hocko wrote: > > > > On Thu 24-10-19 16:34:46, Randy Dunlap wrote: > > > > > [adding linux-mm + people] > > > > > > > > > > On 10/24/19 12:36 AM, Robert Stupp wrote: > > > > > > Hi guys, > > > > > > > > > > > > I've got an issue with `mlockall(MCL_CURRENT)` after > > > > > > upgrading > > > > > > Ubuntu 19.04 to 19.10 - i.e. kernel version change from 5.0.x > > > > > > to > > > > > > 5.3.x. > > > > > > > > > > > > The following simple program hangs forever with one CPU > > > > > > running > > > > > > at 100% (kernel): > > > > > > > > Can you capture everal snapshots of proc/$(pidof $YOURTASK)/stack > > > > while > > > > this is happening? > > > > > > Sure, > > > > > > Approach: > > > - one shell running > > > while true; do cat /proc/$(pidof test)/stack; done > > > - starting ./test in another shell + ctrl-c quite some times > > > > > > Vast majority of all ./test invocations return an empty 'stack' > > > file. > > > Some tries, maybe 1 out of 20, returned these snapshots. > > > Was running 5.3.7 for this test. > > > > > > > > > [<0>] __handle_mm_fault+0x4c5/0x7a0 > > > [<0>] handle_mm_fault+0xca/0x1f0 > > > [<0>] __get_user_pages+0x230/0x770 > > > [<0>] populate_vma_page_range+0x74/0x80 > > > [<0>] __mm_populate+0xb1/0x150 > > > [<0>] __x64_sys_mlockall+0x11c/0x190 > > > [<0>] do_syscall_64+0x5a/0x130 > > > [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > [<0>] __handle_mm_fault+0x4c5/0x7a0 > > > [<0>] handle_mm_fault+0xca/0x1f0 > > > [<0>] __get_user_pages+0x230/0x770 > > > [<0>] populate_vma_page_range+0x74/0x80 > > > [<0>] __mm_populate+0xb1/0x150 > > > [<0>] __x64_sys_mlockall+0x11c/0x190 > > > [<0>] do_syscall_64+0x5a/0x130 > > > [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > > > > > > [<0>] __handle_mm_fault+0x4c5/0x7a0 > > > [<0>] handle_mm_fault+0xca/0x1f0 > > > [<0>] __get_user_pages+0x230/0x770 > > > [<0>] populate_vma_page_range+0x74/0x80 > > > [<0>] __mm_populate+0xb1/0x150 > > > [<0>] __x64_sys_mlockall+0x11c/0x190 > > > [<0>] do_syscall_64+0x5a/0x130 > > > [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > > > > > > [<0>] __do_fault+0x3c/0x130 > > > [<0>] do_fault+0x248/0x640 > > > [<0>] __handle_mm_fault+0x4c5/0x7a0 > > > [<0>] handle_mm_fault+0xca/0x1f0 > > > [<0>] __get_user_pages+0x230/0x770 > > > [<0>] populate_vma_page_range+0x74/0x80 > > > [<0>] __mm_populate+0xb1/0x150 > > > [<0>] __x64_sys_mlockall+0x11c/0x190 > > > [<0>] do_syscall_64+0x5a/0x130 > > > [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > > > > This is expected. > > > > > // doubt this one is relevant > > > [<0>] __wake_up_common_lock+0x7c/0xc0 > > > [<0>] __wake_up_sync_key+0x1e/0x30 > > > [<0>] __wake_up_parent+0x26/0x30 > > > [<0>] do_notify_parent+0x1cc/0x280 > > > [<0>] do_exit+0x703/0xaf0 > > > [<0>] do_group_exit+0x47/0xb0 > > > [<0>] get_signal+0x165/0x880 > > > [<0>] do_signal+0x34/0x280 > > > [<0>] exit_to_usermode_loop+0xbf/0x160 > > > [<0>] do_syscall_64+0x10f/0x130 > > > [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > Hmm, this means that the task has exited so how come there are > > other syscalls happening. Are you sure you are collecting stacks for > > the > > correct task? > > I guess that the `cat /proc/$(pidof test)/stack` captured the stack > after I hit ctrl-c. Does that make sense? > > Also tried `syscall(SYS_mlockall, MCL_CURRENT);` instead of > `mlockall(MCL_CURRENT)` - same behavior. This smells like something that could be runtime specific. Could you post strace output of your testcase? -- Michal Hocko SUSE Labs
