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Since kernel 3.6 a SYNCHRONIZE CACHE command is sent to SCSI disks during the scsi_remove_host() call. That command is sent after command processing has been suspended in SCST and hence causes a deadlock. Avoid this deadlock by failing all commands issued after scst_unregister_target() has been invoked. The output of echo w >/proc/sysrq-trigger just after module removal of scst_local started is as follows: SysRq : Show Blocked State task PC stack pid father kworker/2:1 D ffff88003d08cf40 0 37 2 0x00000000 ffff88003d0bd830 0000000000000046 ffffffff814a849e ffff88003d08cf40 ffff88003d08cf40 ffff88003d0bdfd8 ffff88003d0bdfd8 ffff88003d0bdfd8 ffff88003d9a3b70 ffff88003d08cf40 0000000000000282 ffff88003d0bd860 Call Trace: [<ffffffff814a849e>] ? schedule_timeout+0x12e/0x230 [<ffffffff814aabc9>] schedule+0x29/0x70 [<ffffffff814a84a3>] schedule_timeout+0x133/0x230 [<ffffffff8104cc00>] ? __internal_add_timer+0x140/0x140 [<ffffffff814aaa72>] wait_for_common+0x122/0x170 [<ffffffff81074050>] ? try_to_wake_up+0x2c0/0x2c0 [<ffffffff814aab73>] wait_for_completion_timeout+0x13/0x20 [<ffffffff811edc2b>] blk_execute_rq+0x17b/0x200 [<ffffffff814aa993>] ? wait_for_common+0x43/0x170 [<ffffffff81180a51>] ? bio_phys_segments+0x21/0x30 [<ffffffff811e8cf0>] ? blk_rq_bio_prep+0x30/0xb0 [<ffffffff812e46ee>] scsi_execute+0xee/0x180 [<ffffffff812e58ed>] scsi_execute_req+0xbd/0x130 [<ffffffff812f55c0>] sr_check_events+0xc0/0x2d0 [<ffffffff81076218>] ? sched_clock_cpu+0xa8/0x110 [<ffffffff8131e1cc>] cdrom_check_events+0x1c/0x40 [<ffffffff812f5a39>] sr_block_check_events+0x19/0x20 [<ffffffff811f0e32>] disk_events_workfn+0x62/0x160 [<ffffffff8105affe>] process_one_work+0x1ae/0x620 [<ffffffff8105af9d>] ? process_one_work+0x14d/0x620 [<ffffffff811f0dd0>] ? __disk_unblock_events+0x130/0x130 [<ffffffff8105ce97>] worker_thread+0x187/0x4e0 [<ffffffff8105cd10>] ? manage_workers+0x320/0x320 [<ffffffff81062a07>] kthread+0xb7/0xc0 [<ffffffff81097b35>] ? trace_hardirqs_on_caller+0x105/0x190 [<ffffffff814b5d04>] kernel_thread_helper+0x4/0x10 [<ffffffff814ac870>] ? retint_restore_args+0x13/0x13 [<ffffffff81062950>] ? flush_kthread_work+0x1e0/0x1e0 [<ffffffff814b5d00>] ? gs_change+0x13/0x13 rmmod D ffff88001d46a7a0 0 10456 10437 0x00000004 ffff8800393cd7a8 0000000000000046 ffffffff814a849e ffff88001d46a7a0 ffff88001d46a7a0 ffff8800393cdfd8 ffff8800393cdfd8 ffff8800393cdfd8 ffffffff81a13420 ffff88001d46a7a0 0000000000000282 ffff8800393cd7d8 Call Trace: [<ffffffff814a849e>] ? schedule_timeout+0x12e/0x230 [<ffffffff814aabc9>] schedule+0x29/0x70 [<ffffffff814a84a3>] schedule_timeout+0x133/0x230 [<ffffffff8104cc00>] ? __internal_add_timer+0x140/0x140 [<ffffffff814aaa72>] wait_for_common+0x122/0x170 [<ffffffff81074050>] ? try_to_wake_up+0x2c0/0x2c0 [<ffffffff814aab73>] wait_for_completion_timeout+0x13/0x20 [<ffffffff811edc2b>] blk_execute_rq+0x17b/0x200 [<ffffffff814aa993>] ? wait_for_common+0x43/0x170 [<ffffffff81063000>] ? __init_waitqueue_head+0x60/0x60 [<ffffffff812e46ee>] scsi_execute+0xee/0x180 [<ffffffff812e58ed>] scsi_execute_req+0xbd/0x130 [<ffffffff812f07a8>] sd_sync_cache+0x98/0x120 [<ffffffff812f0a40>] sd_shutdown+0xd0/0x150 [<ffffffff812f0b3c>] sd_remove+0x7c/0xc0 [<ffffffff812c3e6c>] __device_release_driver+0x7c/0xf0 [<ffffffff812c3f0e>] device_release_driver+0x2e/0x40 [<ffffffff812c380f>] bus_remove_device+0xff/0x170 [<ffffffff812c099d>] device_del+0x12d/0x1c0 [<ffffffff812eae1d>] __scsi_remove_device+0x10d/0x120 [<ffffffff812e97ef>] scsi_forget_host+0x6f/0x80 [<ffffffff812deb8a>] scsi_remove_host+0x7a/0x130 [<ffffffffa0287bea>] scst_local_driver_remove+0x5a/0x120 [scst_local] [<ffffffff812c3e6c>] __device_release_driver+0x7c/0xf0 [<ffffffff812c3f0e>] device_release_driver+0x2e/0x40 [<ffffffff812c380f>] bus_remove_device+0xff/0x170 [<ffffffff812c099d>] device_del+0x12d/0x1c0 [<ffffffffa028ae21>] ? scst_local_exit+0x6b/0x24a [scst_local] [<ffffffff812c0a52>] device_unregister+0x22/0x60 [<ffffffffa0287649>] scst_local_remove_adapter+0x59/0xd0 [scst_local] [<ffffffffa02880ab>] __scst_local_remove_target+0x7b/0x130 [scst_local] [<ffffffffa028ae3a>] scst_local_exit+0x84/0x24a [scst_local] [<ffffffff810a2d26>] sys_delete_module+0x1a6/0x2b0 [<ffffffff814ac855>] ? retint_swapgs+0x13/0x1b [<ffffffff8120ebfe>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff814b4b29>] system_call_fastpath+0x16/0x1b Signed-off-by: Bart Van Assche <bvanassche@acm.org> git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4566 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This is the SCST development repository. It contains not a single project SCST as one can think, but a number of them, which are divided as the following: 1. SCST core in scst/ subdirectory 2. Administration utility for SCST core scstadmin in scstadmin/ 3. Target drivers in own subdirectories qla2x00t/, iscsi-scst/, etc. 4. User space programs in usr/ subdirectory, like fileio_tgt. 5. Some various docs in doc/ subdirectory. Those subprojects are in most cases independent from each other, although some of them depend from the SCST core. They put in the single repository only to simplify their development, they are released independently. Thus, use "make all" only if you really need to build everything. Otherwise build only what you need, like for iSCSI-SCST: make scst scst_install iscsi iscsi_install For more information about each subproject see their README files. Vladislav Bolkhovitin <vst@vlnb.net>, http://scst.sourceforge.net