> Then send us those traces. Please try to avoid wordwrapping them in the email. Ok, so I run my simulations, and then run the following script. --- This was run on the master node echo w > /proc/sysrq-trigger dmesg -c -s 1000000 > foo I've captured these stuck tasks on both the master and the slave node, on separate runs. Here is the master capture. --- SysRq : Show Blocked State task PC stack pid father SysRq : Show Blocked State task PC stack pid father nfsd D 00000001079318f8 0 5832 2 ffff880837a23c70 0000000000000046 0000000000000000 0000000000000002 ffff88083aef5950 ffff88083cda5790 ffff88083aef5b80 0000000437a23c80 00000000ffffffff 00000001079318fb 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5840 2 ffff88083725fc70 0000000000000046 0000000000000000 0000000000000002 ffff880838cca8e0 ffffffff8070a340 ffff880838ccab10 000000003725fc80 00000000ffffffff 00000001079318fb 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5847 2 ffff8808369a3c70 0000000000000046 0000000000000000 0000000000000002 ffff880836f88bb0 ffffffff8070a340 ffff880836f88de0 00000000369a3c80 00000000ffffffff 00000001079318f9 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5867 2 ffff88083561fc70 0000000000000046 0000000000000000 0000000000000002 ffff880835422cb0 ffffffff8070a340 ffff880835422ee0 000000003561fc80 00000000ffffffff 00000001079318f8 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5868 2 ffff880835739c70 0000000000000046 0000000000000000 0000000000000002 ffff880835422720 ffffffff8070a340 ffff880835422950 0000000035739c80 00000000ffffffff 00000001079318f9 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5887 2 ffff8808342bbc70 0000000000000046 0000000000000000 0000000000000002 ffff8808340a2db0 ffffffff8070a340 ffff8808340a2fe0 00000000342bbc80 00000000ffffffff 00000001079318f9 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5888 2 ffff8808343b9c70 0000000000000046 0000000000000000 0000000000000002 ffff8808340a2820 ffffffff8070a340 ffff8808340a2a50 00000000343b9c80 00000000ffffffff 00000001079318fb 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5893 2 ffff8808338e7c70 0000000000000046 0000000000000000 0000000000000002 ffff880833dd0860 ffffffff8070a340 ffff880833dd0a90 00000000338e7c80 00000000ffffffff 00000001079318f9 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 nfsd D 00000001079318e9 0 5905 2 ffff880832d41c70 0000000000000046 0000000000000000 0000000000000002 ffff880832d3f9d0 ffffffff8070a340 ffff880832d3fc00 0000000032d41c80 00000000ffffffff 00000001079318fb 0000000000000000 0000000000000000 Call Trace: [<ffffffff8056e8e3>] schedule_timeout+0x8a/0xad [<ffffffff80237e8b>] process_timeout+0x0/0x5 [<ffffffff8056e8de>] schedule_timeout+0x85/0xad [<ffffffff80238178>] msleep+0x14/0x1e [<ffffffff8030235d>] nfsd_vfs_write+0x221/0x2dd [<ffffffff8028222b>] __dentry_open+0x14c/0x23b [<ffffffff80302a93>] nfsd_write+0xc5/0xe2 [<ffffffff803003bd>] nfsd_proc_write+0xc5/0xde [<ffffffff80307ac1>] decode_fh+0x1c/0x45 [<ffffffff802fe8f3>] nfsd_dispatch+0xde/0x1c2 [<ffffffff805456f5>] svc_process+0x408/0x6e7 [<ffffffff8056f920>] __down_read+0x12/0x93 [<ffffffff802fef26>] nfsd+0x1b7/0x285 [<ffffffff802fed6f>] nfsd+0x0/0x285 [<ffffffff80240d34>] kthread+0x47/0x73 [<ffffffff8022bd1d>] schedule_tail+0x27/0x5f [<ffffffff8020c109>] child_rip+0xa/0x11 [<ffffffff80240ced>] kthread+0x0/0x73 [<ffffffff8020c0ff>] child_rip+0x0/0x11 And here's what was caught on the slave node during a separate run. --- SysRq : Show Blocked State task PC stack pid father hello_c D 00000001027c68c2 0 9840 9839 ffff88043b101bf8 0000000000000086 0000000000000000 0000000000000246 ffff88043e58f2c0 ffff88043e4d6bf0 ffff88043e58f4f0 0000000200000246 00000000ffffffff ffffffff805317a9 0000000000000000 0000000000000000 Call Trace: [<ffffffff805317a9>] xprt_prepare_transmit+0x81/0x8c [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff802f58e9>] nfs_wait_bit_killable+0x2a/0x30 [<ffffffff80560e03>] __wait_on_bit+0x40/0x6e [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff80560e9d>] out_of_line_wait_on_bit+0x6c/0x78 [<ffffffff80240e87>] wake_bit_function+0x0/0x23 [<ffffffff802f94b0>] nfs_sync_mapping_wait+0xed/0x21a [<ffffffff802f9672>] nfs_wb_page+0x95/0xc7 [<ffffffff802f9da0>] nfs_flush_incompatible+0x40/0x51 [<ffffffff802eea77>] nfs_vm_page_mkwrite+0xbd/0xf2 [<ffffffff80267f9e>] do_wp_page+0xe3/0x511 [<ffffffff80269a34>] handle_mm_fault+0x665/0x6c1 [<ffffffff8026d46b>] vma_merge+0x147/0x1f4 [<ffffffff80563f91>] do_page_fault+0x43a/0x7f5 [<ffffffff80562049>] error_exit+0x0/0x51 hello_c D 00000001027c68e6 0 9841 9839 ffff88043a0a3bf8 0000000000000086 0000000000000000 ffff88043c491800 ffff88043c9d8660 ffff88043e4a0620 ffff88043c9d8890 000000013c491800 00000000ffffffff ffffffff805307a5 0000000000000000 0000000000000000 Call Trace: [<ffffffff805307a5>] xprt_end_transmit+0x2c/0x39 [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff802f58e9>] nfs_wait_bit_killable+0x2a/0x30 [<ffffffff80560e03>] __wait_on_bit+0x40/0x6e [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff80560e9d>] out_of_line_wait_on_bit+0x6c/0x78 [<ffffffff80240e87>] wake_bit_function+0x0/0x23 [<ffffffff802f94b0>] nfs_sync_mapping_wait+0xed/0x21a [<ffffffff802f9672>] nfs_wb_page+0x95/0xc7 [<ffffffff802f9da0>] nfs_flush_incompatible+0x40/0x51 [<ffffffff802eea77>] nfs_vm_page_mkwrite+0xbd/0xf2 [<ffffffff80267f9e>] do_wp_page+0xe3/0x511 [<ffffffff80269a34>] handle_mm_fault+0x665/0x6c1 [<ffffffff80281f21>] put_unused_fd+0x31/0x3c [<ffffffff80563f91>] do_page_fault+0x43a/0x7f5 [<ffffffff80562049>] error_exit+0x0/0x51 hello_c D ffffffff802f58bf 0 9842 9839 ffff88043b1bdbf8 0000000000000082 ffff88043a0ee688 ffff88043c491800 ffff88043bbc8d30 ffff88043c9a99d0 ffff88043bbc8f60 000000033c491800 ffff88043a0ee688 ffffffff805307a5 ffff88043a0ee688 0000000000000246 Call Trace: [<ffffffff805307a5>] xprt_end_transmit+0x2c/0x39 [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff802f58e9>] nfs_wait_bit_killable+0x2a/0x30 [<ffffffff80560e03>] __wait_on_bit+0x40/0x6e [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff80560e9d>] out_of_line_wait_on_bit+0x6c/0x78 [<ffffffff80240e87>] wake_bit_function+0x0/0x23 [<ffffffff802f94b0>] nfs_sync_mapping_wait+0xed/0x21a [<ffffffff802f9672>] nfs_wb_page+0x95/0xc7 [<ffffffff802f9da0>] nfs_flush_incompatible+0x40/0x51 [<ffffffff802eea77>] nfs_vm_page_mkwrite+0xbd/0xf2 [<ffffffff80267f9e>] do_wp_page+0xe3/0x511 [<ffffffff80269a34>] handle_mm_fault+0x665/0x6c1 [<ffffffff80563f91>] do_page_fault+0x43a/0x7f5 [<ffffffff80562049>] error_exit+0x0/0x51 hello_c D 00000001027c68db 0 9843 9839 ffff88043ac59bf8 0000000000000082 0000000000000000 0000000000000246 ffff88043bbc8210 ffffffff806f9340 ffff88043bbc8440 0000000000000246 00000000ffffffff ffffffff805317a9 0000000000000000 0000000000000000 Call Trace: [<ffffffff805317a9>] xprt_prepare_transmit+0x81/0x8c [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff802f58e9>] nfs_wait_bit_killable+0x2a/0x30 [<ffffffff80560e03>] __wait_on_bit+0x40/0x6e [<ffffffff802f58bf>] nfs_wait_bit_killable+0x0/0x30 [<ffffffff80560e9d>] out_of_line_wait_on_bit+0x6c/0x78 [<ffffffff80240e87>] wake_bit_function+0x0/0x23 [<ffffffff802f94b0>] nfs_sync_mapping_wait+0xed/0x21a [<ffffffff802f9672>] nfs_wb_page+0x95/0xc7 [<ffffffff802f9da0>] nfs_flush_incompatible+0x40/0x51 [<ffffffff802eea77>] nfs_vm_page_mkwrite+0xbd/0xf2 [<ffffffff80267f9e>] do_wp_page+0xe3/0x511 [<ffffffff80269a34>] handle_mm_fault+0x665/0x6c1 [<ffffffff80563f91>] do_page_fault+0x43a/0x7f5 [<ffffffff80562049>] error_exit+0x0/0x51 -- To 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