Issue

• The problem is the Infiniband driver can deadlock with itself if a page fault happens while it has a mm_struct.mmap_sem structure locked.

• There will be messages like the following in the system log file.

INFO: task cl5936_main_lin:21734 blocked for more than 120 seconds. 
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. 
cl5936_main_l D 000000000000000a     0 21734  21730 0x00000080 
 ffff8804307cdca0 0000000000000086 0000000000000000 ffff880880018e18 
 00000037ffffffc8 ffff880880021b40 0000000000000000 ffff880800000041 
 ffff880736fd5078 ffff8804307cdfd8 000000000000f4e8 ffff880736fd5078 
Call Trace: 
 [<ffffffff814eefb5>] rwsem_down_failed_common+0x95/0x1d0 
 [<ffffffff811238a1>] ? __alloc_pages_nodemask+0x111/0x940 
 [<ffffffff814ef146>] rwsem_down_read_failed+0x26/0x30 
 [<ffffffff81276e04>] call_rwsem_down_read_failed+0x14/0x30 
 [<ffffffff814ee644>] ? down_read+0x24/0x30 
 [<ffffffffa00191f2>] kcopy_get_pages+0xf2/0x190 [kcopy] 
 [<ffffffffa001963b>] kcopy_write+0x3ab/0x5d0 [kcopy] 
 [<ffffffff81052600>] ? __dequeue_entity+0x30/0x50 
 [<ffffffff811765d8>] vfs_write+0xb8/0x1a0 
 [<ffffffff810d46e2>] ? audit_syscall_entry+0x272/0x2a0 
 [<ffffffff81176fe1>] sys_write+0x51/0x90 
 [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b 
INFO: task cl5936_main_lin:21735 blocked for more than 120 seconds. 
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. 
cl5936_main_l D 0000000000000003     0 21735  21730 0x00000080 
 ffff880868e7b870 0000000000000082 0000000000000000 ffffea000180a538 
 ffffea000180a500 ffffea000180a4c8 ffffea000180a490 ffff880868e7b7e8 
 ffff88085de230f8 ffff880868e7bfd8 000000000000f4e8 ffff88085de230f8 
Call Trace: 
 [<ffffffff8112a862>] ? shrink_inactive_list+0x4f2/0x740 
 [<ffffffff814eefb5>] rwsem_down_failed_common+0x95/0x1d0 
 [<ffffffff814ef146>] rwsem_down_read_failed+0x26/0x30 
 [<ffffffff81276e04>] call_rwsem_down_read_failed+0x14/0x30 
 [<ffffffff814ee644>] ? down_read+0x24/0x30 
 [<ffffffff81042b87>] __do_page_fault+0x187/0x480 
 [<ffffffff8116e0ed>] ? follow_trans_huge_pmd+0xed/0xf0 
 [<ffffffff8116e0c9>] ? follow_trans_huge_pmd+0xc9/0xf0 
 [<ffffffff8100bcee>] ? invalidate_interrupt5+0xe/0x20 
 [<ffffffff814f248e>] do_page_fault+0x3e/0xa0 
 [<ffffffff814ef845>] page_fault+0x25/0x30 
 [<ffffffff812759ed>] ? copy_use- r_generic_string+0x2d/0x40 
 [<ffffffffa015604b>] ? qib_user_sdma_writev+0x24b/0x1380 [ib_qib] 
 [<ffffffffa012efb0>] ? qib_aio_write+0x0/0x50 [ib_qib] 
 [<ffffffffa012eff3>] qib_aio_write+0x43/0x50 [ib_qib] 
 [<ffffffff8117619b>] do_sync_readv_writev+0xfb/0x140 
 [<ffffffff81090bf0>] ? autoremove_wake_function+0x0/0x40 
 [<ffffffff81055c83>] ? perf_event_task_sched_out+0x33/0x80 
 [<ffffffff8120c3c6>] ? security_file_permission+0x16/0x20 
 [<ffffffff8117722f>] do_readv_writev+0xcf/0x1f0 
 [<ffffffff814eca40>] ? thread_return+0x4e/0x77e 
 [<ffffffff81177396>] vfs_writev+0x46/0x60 
 [<ffffffff811774c1>] sys_writev+0x51/0xb0 
 [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b 

• In the displayed stack traces there may be one or more procedure names starting with qib.

 Examples :     qib_aio_write+0x43/0x50 [ib_qib] 
                ? qib_user_sdma_writev+0x24b/0x1380 [ib_qib]

• Processes that use the files ‘/proc/*/cmdline’ such the ps command does may also be hung.