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when one of its LUNs is a CD-ROM device. sr_block_release() invokes scst_local_release_adapter() indirectly with sr_mutex held. So if scst_local_release_adapter() blocks until the scst_local session has been freed a deadlock may be triggered if another CD-ROM device has to be closed in order to free that session. Fix this by changing scst_local_release_adapter() such that it does not wait until the session unregistration has finished. Call stacks obtained with echo w > /proc/sysrq-trigger: SysRq : Show Blocked State task PC stack pid father scst_mgmtd D ffffffff812f979d 0 5552 2 0x00000000 ffff88003c335b30 0000000000000046 ffffffff812f979d 0000000000000002 ffff8800171d47a0 ffff88003c335fd8 ffff88003c335fd8 ffff88003c335fd8 ffff88003d1b0000 ffff8800171d47a0 ffff88003c335b60 ffff88003c334000 Call Trace: [<ffffffff812f979d>] ? sr_block_release+0x2d/0x60 [<ffffffff812f979d>] ? sr_block_release+0x2d/0x60 [<ffffffff814a9b19>] schedule+0x29/0x70 [<ffffffff814a9e57>] schedule_preempt_disabled+0x27/0x40 [<ffffffff814a79b7>] mutex_lock_nested+0x187/0x390 [<ffffffff812f979d>] ? sr_block_release+0x2d/0x60 [<ffffffff812f979d>] sr_block_release+0x2d/0x60 [<ffffffff8118a1ec>] __blkdev_put+0x19c/0x1d0 [<ffffffff8118a27d>] blkdev_put+0x5d/0x180 [<ffffffff8118a3c8>] blkdev_close+0x28/0x30 [<ffffffff81153633>] fput+0x103/0x280 [<ffffffff8114fad9>] filp_close+0x69/0x90 [<ffffffffa022ec24>] vdisk_detach_tgt+0x134/0x150 [scst_vdisk] [<ffffffffa02d8f2f>] scst_free_tgt_dev+0xdf/0x220 [scst] [<ffffffffa02d949f>] ? scst_free_session_callback+0x7f/0x170 [scst] [<ffffffffa02d90eb>] scst_sess_free_tgt_devs+0x7b/0x110 [scst] [<ffffffffa02d91de>] scst_free_session+0x5e/0x2a0 [scst] [<ffffffffa02d94be>] scst_free_session_callback+0x9e/0x170 [scst] [<ffffffffa02c6a05>] scst_global_mgmt_thread+0x2e5/0x580 [scst] [<ffffffff8105e850>] ? __init_waitqueue_head+0x60/0x60 [<ffffffffa02c6720>] ? scst_register_session_non_gpl+0x20/0x20 [scst] [<ffffffff8105dd77>] kthread+0xb7/0xc0 [<ffffffff814b50b4>] kernel_thread_helper+0x4/0x10 [<ffffffff814abb30>] ? retint_restore_args+0x13/0x13 [<ffffffff8105dcc0>] ? __init_kthread_worker+0x70/0x70 [<ffffffff814b50b0>] ? gs_change+0x13/0x13 iscsi-scstd D ffffffffa02b1b1f 0 5567 1 0x00000004 ffff88003c2f59a8 0000000000000046 ffffffffa02b1b1f 0000000000000002 ffff8800173b23d0 ffff88003c2f5fd8 ffff88003c2f5fd8 ffff88003c2f5fd8 ffff88003d198000 ffff8800173b23d0 ffff88003c2f59d8 ffff88003c2f4000 Call Trace: [<ffffffffa02b1b1f>] ? scst_unregister_target+0x8f/0x450 [scst] [<ffffffffa02b1b1f>] ? scst_unregister_target+0x8f/0x450 [scst] [<ffffffff814a9b19>] schedule+0x29/0x70 [<ffffffff814a9e57>] schedule_preempt_disabled+0x27/0x40 [<ffffffff814a79b7>] mutex_lock_nested+0x187/0x390 [<ffffffffa02b1b1f>] ? scst_unregister_target+0x8f/0x450 [scst] [<ffffffffa025c7ba>] ? __iscsi_del_attr+0xea/0x190 [iscsi_scst] [<ffffffffa02b1b1f>] scst_unregister_target+0x8f/0x450 [scst] [<ffffffffa025c7ba>] ? __iscsi_del_attr+0xea/0x190 [iscsi_scst] [<ffffffffa026249f>] target_destroy+0x5f/0xc0 [iscsi_scst] [<ffffffffa02631f2>] target_del_all+0xf2/0x2d0 [iscsi_scst] [<ffffffffa025c8aa>] release+0x4a/0xe0 [iscsi_scst] [<ffffffff81153633>] fput+0x103/0x280 [<ffffffff8114fad9>] filp_close+0x69/0x90 [<ffffffff8103e533>] put_files_struct+0x103/0x1c0 [<ffffffff8103e478>] ? put_files_struct+0x48/0x1c0 [<ffffffff8103e6b2>] exit_files+0x52/0x60 [<ffffffff8103eb80>] do_exit+0x180/0x8e0 [<ffffffff8104ef87>] ? get_signal_to_deliver+0xe7/0x6e0 [<ffffffff8103f631>] do_group_exit+0x51/0xc0 [<ffffffff8104f0bf>] get_signal_to_deliver+0x21f/0x6e0 [<ffffffff8100223c>] do_signal+0x3c/0x580 [<ffffffff81002805>] do_notify_resume+0x65/0xa0 [<ffffffff812149de>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff814b4122>] int_signal+0x12/0x17 rmmod D ffffffffa02b1b70 0 5714 5681 0x00000000 ffff88000b497d48 0000000000000046 ffffffffa02b1b70 0000000000000002 ffff88003920a3d0 ffff88000b497fd8 ffff88000b497fd8 ffff88000b497fd8 ffff88003d17a3d0 ffff88003920a3d0 ffff88000b497d78 ffff88000b496000 Call Trace: [<ffffffffa02b1b70>] ? scst_unregister_target+0xe0/0x450 [scst] [<ffffffffa02b1b70>] ? scst_unregister_target+0xe0/0x450 [scst] [<ffffffff814a9b19>] schedule+0x29/0x70 [<ffffffff814a9e57>] schedule_preempt_disabled+0x27/0x40 [<ffffffff814a79b7>] mutex_lock_nested+0x187/0x390 [<ffffffffa02b1b70>] ? scst_unregister_target+0xe0/0x450 [scst] [<ffffffffa02b1b70>] scst_unregister_target+0xe0/0x450 [scst] [<ffffffffa0287e51>] ? scst_local_exit+0x6b/0x21a [scst_local] [<ffffffff812c2d37>] ? put_device+0x17/0x20 [<ffffffff812c3efa>] ? device_unregister+0x2a/0x60 [<ffffffffa0285108>] __scst_local_remove_target+0xa8/0x130 [scst_local] [<ffffffffa0287e6a>] scst_local_exit+0x84/0x21a [scst_local] [<ffffffff810a40c6>] sys_delete_module+0x1a6/0x2b0 [<ffffffff812149de>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff814b3de9>] system_call_fastpath+0x16/0x1b ata_id D ffff88003920c7a0 0 5715 5195 0x00000000 ffff880015e97818 0000000000000046 0000000000000000 0000000000000046 ffff88003920c7a0 ffff880015e97fd8 ffff880015e97fd8 ffff880015e97fd8 ffff880021788000 ffff88003920c7a0 ffff880015e977f8 7fffffffffffffff Call Trace: [<ffffffff814a9b19>] schedule+0x29/0x70 [<ffffffff814a7355>] schedule_timeout+0x315/0x390 [<ffffffff814a98e3>] ? wait_for_common+0x43/0x170 [<ffffffff814a98e3>] ? wait_for_common+0x43/0x170 [<ffffffff814a99c2>] wait_for_common+0x122/0x170 [<ffffffff810705b0>] ? try_to_wake_up+0x2f0/0x2f0 [<ffffffff814a9aed>] wait_for_completion+0x1d/0x20 [<ffffffffa02bfad3>] scst_unregister_session+0x1a3/0x320 [scst] [<ffffffffa0284990>] scst_local_release_adapter+0xa0/0x140 [scst_local] [<ffffffff812c2f87>] device_release+0x27/0xa0 [<ffffffff81209abb>] kobject_release+0x8b/0x1d0 [<ffffffff8120993c>] kobject_put+0x2c/0x60 [<ffffffff812c2d37>] put_device+0x17/0x20 [<ffffffff812e1850>] scsi_host_dev_release+0xc0/0xe0 [<ffffffff812c2f87>] device_release+0x27/0xa0 [<ffffffff81209abb>] kobject_release+0x8b/0x1d0 [<ffffffff8120993c>] kobject_put+0x2c/0x60 [<ffffffff812c2d37>] put_device+0x17/0x20 [<ffffffff812ea0c2>] scsi_target_dev_release+0x22/0x30 [<ffffffff812c2f87>] device_release+0x27/0xa0 [<ffffffff81209abb>] kobject_release+0x8b/0x1d0 [<ffffffff8120993c>] kobject_put+0x2c/0x60 [<ffffffff812c2d37>] put_device+0x17/0x20 [<ffffffff812ed818>] scsi_device_dev_release_usercontext+0x118/0x130 [<ffffffff812ed700>] ? scsi_device_cls_release+0x20/0x20 [<ffffffff81056576>] execute_in_process_context+0x86/0xa0 [<ffffffff812ed6dc>] scsi_device_dev_release+0x1c/0x20 [<ffffffff812c2f87>] device_release+0x27/0xa0 [<ffffffff81209abb>] kobject_release+0x8b/0x1d0 [<ffffffff8120993c>] kobject_put+0x2c/0x60 [<ffffffff812c2d37>] put_device+0x17/0x20 [<ffffffff812df594>] scsi_device_put+0x44/0x60 [<ffffffff812f974d>] scsi_cd_put+0x4d/0x70 [<ffffffff812f97b1>] sr_block_release+0x41/0x60 [<ffffffff8118a1ec>] __blkdev_put+0x19c/0x1d0 [<ffffffff8118a27d>] blkdev_put+0x5d/0x180 [<ffffffff8118a3c8>] blkdev_close+0x28/0x30 [<ffffffff81153633>] fput+0x103/0x280 [<ffffffff814a93b3>] ? __schedule+0x3c3/0x820 [<ffffffff8114fad9>] filp_close+0x69/0x90 [<ffffffff8114fba0>] sys_close+0xa0/0x100 [<ffffffff814b3de9>] system_call_fastpath+0x16/0x1b Signed-off-by: Bart Van Assche <bvanassche@acm.org> Cc: Richard Sharpe <realrichardsharpe@gmail.com> git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4425 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