On 02/09/2015 10:46 AM, Konstantin Khlebnikov wrote: > On Mon, Feb 9, 2015 at 12:36 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote: >> On 02/09/2015 08:14 AM, Konstantin Khlebnikov wrote: >>> Python was running under ptrace-based sandbox "sydbox" used exherbo >>> chroot. Kernel: 3.18.6 + my patch "mm: prevent endless growth of >>> anon_vma hierarchy" (patch seems stable). >>> >>> [ 4674.087780] INFO: task python:25873 blocked for more than 120 seconds. >>> [ 4674.087793] Tainted: G U 3.18.6-zurg+ #158 >>> [ 4674.087797] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" >>> disables this message. >>> [ 4674.087801] python D ffff88041e2d2000 14176 25873 25630 0x00000102 >>> [ 4674.087817] ffff880286247b68 0000000000000086 ffff8803d5fe6b40 >>> 0000000000012000 >>> [ 4674.087824] ffff880286247fd8 0000000000012000 ffff88040c16eb40 >>> ffff8803d5fe6b40 >>> [ 4674.087830] 0000000300000003 ffff8803d5fe6b40 ffff880362888e78 >>> ffff880362888e60 >>> [ 4674.087836] Call Trace: >>> [ 4674.087854] [<ffffffff81696be9>] schedule+0x29/0x70 >>> [ 4674.087865] [<ffffffff81699815>] rwsem_down_write_failed+0x1d5/0x2f0 >>> [ 4674.087873] [<ffffffff812d4c73>] call_rwsem_down_write_failed+0x13/0x20 >>> [ 4674.087881] [<ffffffff816990c1>] ? down_write+0x31/0x50 >>> [ 4674.087891] [<ffffffff811f3b44>] do_coredump+0x144/0xee0 >>> [ 4674.087900] [<ffffffff810b66f7>] ? pick_next_task_fair+0x397/0x450 >>> [ 4674.087909] [<ffffffff810026a6>] ? __switch_to+0x1d6/0x5f0 >>> [ 4674.087915] [<ffffffff816966e6>] ? __schedule+0x3a6/0x880 >>> [ 4674.087924] [<ffffffff81690000>] ? klist_remove+0x40/0xd0 >>> [ 4674.087932] [<ffffffff81093988>] get_signal+0x298/0x6b0 >>> [ 4674.087940] [<ffffffff81003588>] do_signal+0x28/0xbb0 >>> [ 4674.087946] [<ffffffff8109276d>] ? do_send_sig_info+0x5d/0x80 >>> [ 4674.087955] [<ffffffff81004179>] do_notify_resume+0x69/0xb0 >>> [ 4674.087963] [<ffffffff8169b028>] int_signal+0x12/0x17 >>> >>> Maybe this guy did something wrong? >> >> Well he has do_coredump on stack, so he did something wrong in userspace? But >> here he's just waiting on down_write. Unless there's some bug in do_coredump >> that would lock for read and then for write, without an unlock in between? > > I mean khugepaged. This code looks really messy. Maybe it already has > mmap_sem locked for read and tries to lock it again: Yeah it is messy, and incidentally I'm trying to change how it works. But I didn't find such double lock bug there. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>