<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> Tejasvi Aswathanarayana wrote: <blockquote TYPE=CITE>Crash exits with an error "cannot determine pid_hash array dimensions". Looking at the crash change log, it appears that it was fixed in 4.0-2.24 for the 2.6.17 kernel. The core I have is of a 2.6.16.13 xenified kernel. Is the fix even relevant ? <output> $ ./crash vmlinux-2.6.16.13-xen test.core crash 4.0-3.5 Copyright (C) 2002, 2003, 2004, 2005, 2006 Red Hat, Inc. Copyright (C) 2004, 2005, 2006 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005 Fujitsu Limited Copyright (C) 2005 NEC Corporation Copyright (C) 1999, 2002 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. This program is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Enter "help copying" to see the conditions. This program has absolutely no warranty. Enter "help warranty" for details. GNU gdb 6.1 Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-unknown-linux-gnu"... please wait... (gathering task table data) crash: cannot determine pid_hash array dimensions </output> Is there a way I can get crash's source at releases 4.0-2.24 and 4.0-2.23 so that I can try a fix for this kernel in case it is a specific kernel fix ? Thanks -Tejasvi</blockquote> <tt>Interesting -- I got a private message yesterday from another</tt> <tt>2.6.16-era xen user with the same problem.</tt><tt></tt> <tt>Anyway, over time the manner of pid table handling has</tt> <tt>changed several times, and so to handle the various manners,</tt> <tt>the crash utility's task_init() function assigns an appropriate</tt> <tt>function to gather all pids/tasks running on the system.</tt><tt></tt> <tt>You're referring to this entry in the changelog:</tt><tt></tt> <tt>4.0-2.24 - Fix for 2.6.17 kernels that do not use "pgdat_list" memory node</tt> <tt> list header, which would cause crash to fail during initialization</tt> <tt> with a "crash: cannot resolve: pgdat_list" error message.</tt> <tt> (anderson@redhat.com)</tt><tt></tt> <tt> - Fix for 2.6.17 kernels that have re-worked the kernel pid_hash</tt> <tt> handling, which would cause crash to fail during initialization</tt> <tt> with a "crash: cannot determine pid_hash array dimensions" error</tt> <tt> message. (anderson@redhat.com)</tt> <tt>...</tt> <tt></tt> <tt></tt> <tt>The change above implemented yet another pid hash handler</tt> <tt>called refresh_hlist_task_table_v2(), which as the comments</tt> <tt>above indicate, was required for 2.6.17 kernels. In crash</tt> <tt>version 4.0-2.24, a new refresh_hlist_task_table_v2() function</tt> <tt>was added to replace refresh_hlist_task_table(), to account</tt> <tt>for this change:</tt><tt></tt> <tt>/*</tt> <tt> * 2.6.17 replaced:</tt> <tt> * static struct hlist_head *pid_hash[PIDTYPE_MAX];</tt> <tt> * with</tt> <tt> * static struct hlist_head *pid_hash;</tt> <tt> */</tt><tt></tt> <tt>So, for starters, can you display how "pid_hash" is</tt> <tt>declared in your kernel?</tt><tt></tt> <tt>Unfortunately the only 2.6.16-era x86_64 kernel dumpfile that</tt> <tt>I have on-hand as a reference is an early kdump dumpfile,</tt> <tt>(non-xen) which selects the older refresh_hlist_task_table():</tt><tt></tt> <tt>crash> sys</tt> <tt> KERNEL: /usr/dumps/kdump/vmlinux (2.6.16-20-smp)</tt> <tt> DUMPFILE: /usr/dumps/kdump/vmcore</tt> <tt> CPUS: 2</tt> <tt> DATE: Mon Apr 24 11:02:03 2006</tt> <tt> UPTIME: 00:31:04</tt> <tt>LOAD AVERAGE: 0.00, 0.00, 0.00</tt> <tt> TASKS: 63</tt> <tt> NODENAME: elm3a242</tt> <tt> RELEASE: 2.6.16-20-smp</tt> <tt> VERSION: #1 SMP Mon Apr 10 04:51:13 UTC 2006</tt> <tt> MACHINE: x86_64 (3000 Mhz)</tt> <tt> MEMORY: 4.6 GB</tt> <tt> PANIC: "SysRq : Trigger a crashdump"</tt> <tt>crash> help -t</tt> <tt> current: 1678f60 [62]</tt> <tt> .pid: 3235</tt> <tt> .comm: "bash"</tt> <tt> .task: ffff810121a7d810</tt> <tt> .thread_info: ffff81011d826000</tt> <tt> .processor: 1</tt> <tt> .ptask: ffff810121d91790</tt> <tt> .mm_struct: ffff810122f9eb00</tt> <tt> .tc_next: 0</tt> <tt> context_array: 1677df0</tt> <tt>refresh_task_table: refresh_hlist_task_table()</tt> <tt>...</tt> <tt> </tt> <tt>This is the code sequence in task_init() that selects</tt> <tt>refresh_hlist_task_table() or refresh_hlist_task_table_v2():</tt><tt></tt> <tt> } else {</tt> <tt> tt->pidhash_addr = symbol_value("pid_hash");</tt> <tt> if (!get_array_length("pid_hash", NULL, sizeof(void *)) &&</tt> <tt> VALID_STRUCT(pid_link))</tt> <tt> tt->refresh_task_table = refresh_hlist_task_table_v2;</tt> <tt> else</tt> <tt> tt->refresh_task_table = refresh_hlist_task_table;</tt> <tt> }</tt><tt></tt> <tt>Since you are breaking down on initialization, can you put</tt> <tt>some debug code in place that displays?:</tt><tt></tt> <tt>1. the output of the get_array_length("pid_hash",...) call, and</tt> <tt>2. the output of VALID_STRUCT(pid_link)</tt><tt></tt> <tt>Something must be slightly different between the mainline</tt> <tt>and xen 2.6.16-era kernels.</tt><tt></tt> <tt>What appears to be happening is that refresh_hlist_task_table()</tt> <tt>is being selected, but in that function, this subsequent call</tt> <tt>is failing:</tt><tt></tt> <tt> if (!(plen = get_array_length("pid_hash", NULL, sizeof(void *))))</tt> <tt> error(FATAL, "cannot determine pid_hash array dimensions\n");</tt><tt></tt> <tt>Alternatively, if you want to make the vmlinux/dumpfile pair</tt> <tt>available to me, I can take a look at it.</tt><tt></tt> <tt>Thanks,</tt> <tt> Dave</tt> <tt></tt> <tt></tt> <tt></tt> <tt></tt> <tt></tt> </html>