That was caused by backport of 33692f27597fcab536d7cbbcc8f52905133e4aa7
("vm: add VM_FAULT_SIGSEGV handling support") into v3.18.y without
commit 7fb08eca45270d0ae86e1ad9d39c40b7a55d0190
("x86: mm: move mmap_sem unlock from mm_fault_error() to caller")
which have moved mmap_sem around.On Mon, Feb 9, 2015 at 1:34 PM, Vlastimil Babka <[email protected]> wrote: > On 02/09/2015 10:46 AM, Konstantin Khlebnikov wrote: >> On Mon, Feb 9, 2015 at 12:36 PM, Vlastimil Babka <[email protected]> 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
