Some of my blocked processes are starting to generate stack traces from the kernel:

Jul  1 08:11:43 carina kernel: [36142.699465] INFO: task chrome:2165 blocked for more than 120 seconds.
Jul  1 08:11:43 carina kernel: [36142.699469] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jul  1 08:11:43 carina kernel: [36142.699472] chrome          D 0000000000000004     0  2165      1 0x00000000
Jul  1 08:11:43 carina kernel: [36142.699477]  ffff8804005f5e48 0000000000000086 ffff8804005f5fd8 ffff8804005f4000
Jul  1 08:11:43 carina kernel: [36142.699482]  0000000000013d00 ffff88040dfa4858 ffff8804005f5fd8 0000000000013d00
Jul  1 08:11:43 carina kernel: [36142.699486]  ffff88041f982dc0 ffff88040dfa44a0 0000000c00000001 ffff88040dfa44a0
Jul  1 08:11:43 carina kernel: [36142.699491] Call Trace:
Jul  1 08:11:43 carina kernel: [36142.699501]  [<ffffffff815c2a1d>] rwsem_down_failed_common+0xcd/0x170
Jul  1 08:11:43 carina kernel: [36142.699505]  [<ffffffff815c2ad3>] rwsem_down_write_failed+0x13/0x20
Jul  1 08:11:43 carina kernel: [36142.699511]  [<ffffffff812e6ac3>] call_rwsem_down_write_failed+0x13/0x20
Jul  1 08:11:43 carina kernel: [36142.699515]  [<ffffffff815c1dd2>] ? down_write+0x32/0x40
Jul  1 08:11:43 carina kernel: [36142.699521]  [<ffffffff8126ebf0>] sys_shmdt+0x60/0x180
Jul  1 08:11:43 carina kernel: [36142.699526]  [<ffffffff8100c002>] system_call_fastpath+0x16/0x1b
Jul  1 08:11:43 carina kernel: [36142.699530] INFO: task chrome:2182 blocked for more than 120 seconds.
Jul  1 08:11:43 carina kernel: [36142.699532] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jul  1 08:11:43 carina kernel: [36142.699534] chrome          D 0000000000000000     0  2182      1 0x00000000
Jul  1 08:11:43 carina kernel: [36142.699538]  ffff8804029f5a98 0000000000000086 ffff8804029f5fd8 ffff8804029f4000
Jul  1 08:11:43 carina kernel: [36142.699542]  0000000000013d00 ffff88041030df38 ffff8804029f5fd8 0000000000013d00
Jul  1 08:11:43 carina kernel: [36142.699547]  ffffffff81a0b020 ffff88041030db80 ffff8800bf7542a8 ffff8800bf413d00
Jul  1 08:11:43 carina kernel: [36142.699551] Call Trace:
Jul  1 08:11:43 carina kernel: [36142.699567]  [<ffffffffa0b666b0>] ? nfs_wait_bit_uninterruptible+0x0/0x20 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699571]  [<ffffffff815c0980>] io_schedule+0x70/0xc0
Jul  1 08:11:43 carina kernel: [36142.699582]  [<ffffffffa0b666be>] nfs_wait_bit_uninterruptible+0xe/0x20 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699586]  [<ffffffff815c12ff>] __wait_on_bit+0x5f/0x90
Jul  1 08:11:43 carina kernel: [36142.699597]  [<ffffffffa0b666b0>] ? nfs_wait_bit_uninterruptible+0x0/0x20 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699601]  [<ffffffff815c13ac>] out_of_line_wait_on_bit+0x7c/0x90
Jul  1 08:11:43 carina kernel: [36142.699606]  [<ffffffff81087f70>] ? wake_bit_function+0x0/0x50
Jul  1 08:11:43 carina kernel: [36142.699616]  [<ffffffffa0b66a66>] nfs_wait_on_request+0x36/0x40 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699628]  [<ffffffffa0b6c933>] nfs_try_to_update_request+0x83/0x160 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699640]  [<ffffffffa0b6ca4d>] nfs_writepage_setup+0x3d/0x1e0 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699652]  [<ffffffffa0b6cc73>] nfs_updatepage+0x83/0x180 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699663]  [<ffffffffa0b66949>] ? nfs_release_request+0x19/0x20 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699671]  [<ffffffffa0b5b376>] nfs_vm_page_mkwrite+0x106/0x160 [nfs]
Jul  1 08:11:43 carina kernel: [36142.699676]  [<ffffffff8112e8c4>] do_wp_page+0x584/0x770
Jul  1 08:11:43 carina kernel: [36142.699679]  [<ffffffff8117d5af>] ? touch_atime+0x5f/0x180
Jul  1 08:11:43 carina kernel: [36142.699683]  [<ffffffff81130aab>] handle_pte_fault+0x1db/0x210
Jul  1 08:11:43 carina kernel: [36142.699687]  [<ffffffff81131d4d>] handle_mm_fault+0x16d/0x250
Jul  1 08:11:43 carina kernel: [36142.699691]  [<ffffffff815c6a47>] do_page_fault+0x1a7/0x540
Jul  1 08:11:43 carina kernel: [36142.699696]  [<ffffffff81164fd0>] ? vfs_read+0x120/0x180
Jul  1 08:11:43 carina kernel: [36142.699699]  [<ffffffff815c34d5>] page_fault+0x25/0x30