From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian King Subject: call_usermodehelper hang Date: Tue, 06 Apr 2004 12:03:49 -0500 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <4072E2F5.9060604@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from e32.co.us.ibm.com ([32.97.110.130]:9428 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S263919AbUDFRDw (ORCPT ); Tue, 6 Apr 2004 13:03:52 -0400 Received: from westrelay02.boulder.ibm.com (westrelay02.boulder.ibm.com [9.17.195.11]) by e32.co.us.ibm.com (8.12.10/8.12.2) with ESMTP id i36H3pih739752 for ; Tue, 6 Apr 2004 13:03:51 -0400 List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org Cc: brking@us.ibm.com I have been running into some kernel hangs due to call_usermodehelper. Looking at the backtrace, it looks to me like there are deadlock issues with adding devices from work queues. Attached is a sample backtrace from one of the hangs I experienced. My question is why does call_usermodehelper do 2 different things depending on whether or not it is called from the kevent task? It appears that the simple way to fix the hang would be to never have call_usermodehelper use a work_queue since it must be called from process context anyway, or am I missing something? 0xc0000000017df300 1 0 0 0 D 0xc0000000017df7b0 swapper SP(esp) PC(eip) Function(args) 0xc00000003fc9f460 0x0000000000000000 NO_SYMBOL or Userspace 0xc00000003fc9f4f0 0xc000000000058c40 .schedule +0xb4 0xc00000003fc9f5c0 0xc00000000005a464 .wait_for_completion +0x138 0xc00000003fc9f6c0 0xc00000000007c594 .call_usermodehelper +0x104 0xc00000003fc9f810 0xc00000000022d3e8 .kobject_hotplug +0x3c4 0xc00000003fc9f900 0xc00000000022d67c .kobject_add +0x134 0xc00000003fc9f9a0 0xc00000000012b3d8 .register_disk +0x70 0xc00000003fc9fa40 0xc00000000027dfe4 .add_disk +0x60 0xc00000003fc9fad0 0xc0000000002dc7dc .sd_probe +0x290 0xc00000003fc9fb80 0xc00000000026fbe8 .bus_match +0x94 0xc00000003fc9fc10 0xc00000000026ff70 .driver_attach +0x8c 0xc00000003fc9fca0 0xc000000000270104 .bus_add_driver +0x110 0xc00000003fc9fd50 0xc000000000270a18 .driver_register +0x38 0xc00000003fc9fdd0 0xc0000000002cd8f8 .scsi_register_driver +0x28 0xc00000003fc9fe50 0xc0000000004941d8 .init_sd +0x8c 0xc00000003fc9fee0 0xc00000000000c720 .init +0x25c 0xc00000003fc9ff90 0xc0000000000183ec .kernel_thread +0x4c 0xc00000003fab3380 4 1 0 0 D 0xc00000003fab3830 events/0 SP(esp) PC(eip) Function(args) 0xc00000003faaf6e0 0x0000000000000000 NO_SYMBOL or Userspace 0xc00000003faaf770 0xc000000000058c40 .schedule +0xb4 0xc00000003faaf840 0xc00000000022fa20 .rwsem_down_write_failed +0x14c 0xc00000003faaf910 0xc00000000026fed0 .bus_add_device +0x11c 0xc00000003faaf9b0 0xc00000000026e288 .device_add +0xd0 0xc00000003faafa50 0xc0000000002cdb00 .scsi_sysfs_add_sdev +0x8c 0xc00000003faafb00 0xc0000000002cbff8 .scsi_probe_and_add_lun +0xb04 0xc00000003faafc00 0xc0000000002ccca0 .scsi_add_device +0x90 0xc00000003faafcb0 0xc0000000002d9458 .ipr_worker_thread +0xc60 0xc00000003faafdc0 0xc00000000007cd9c .worker_thread +0x268 0xc00000003faafee0 0xc0000000000839cc .kthread +0x160 0xc00000003faaff90 0xc0000000000183ec .kernel_thread +0x4c -- Brian King eServer Storage I/O IBM Linux Technology Center