From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756008AbaHATQK (ORCPT ); Fri, 1 Aug 2014 15:16:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:25393 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751694AbaHATQH (ORCPT ); Fri, 1 Aug 2014 15:16:07 -0400 Message-ID: <53DBE764.8050109@redhat.com> Date: Fri, 01 Aug 2014 15:15:48 -0400 From: Prarit Bhargava User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131028 Thunderbird/17.0.10 MIME-Version: 1.0 To: Stephen Boyd CC: Saravana Kannan , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Viresh Kumar , Lenny Szubowicz , linux-pm@vger.kernel.org Subject: Re: [PATCH] cpufreq, store_scaling_governor requires policy->rwsem to be held for duration of changing governors [v2] References: <1406634362-811-1-git-send-email-prarit@redhat.com> <2066166.pXm4lKLOID@vostro.rjw.lan> <53DA8389.80804@redhat.com> <1917362.abr2Y4p7vh@vostro.rjw.lan> <53DA8A41.2030601@redhat.com> <53DAA60B.6040802@codeaurora.org> <53DAA749.5080506@redhat.com> <53DAA95B.2040505@codeaurora.org> <53DAB038.3050007@redhat.com> <53DABFA6.6090503@codeaurora.org> <53DACA26.1000908@redhat.com> <53DAE592.2030909@codeaurora.org> <53DB6B81.6050400@redhat.com> <53DBCBE8.6010809@codeaurora.org> In-Reply-To: <53DBCBE8.6010809@codeaurora.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/01/2014 01:18 PM, Stephen Boyd wrote: > On 08/01/14 03:27, Prarit Bhargava wrote: >> >> Can you send me the test and the trace of the deadlock? I'm not creating it with: >> > > This was with conservative as the default, and switching to ondemand > > # cd /sys/devices/system/cpu/cpu2/cpufreq > # ls > affected_cpus scaling_available_governors > conservative scaling_cur_freq > cpuinfo_cur_freq scaling_driver > cpuinfo_max_freq scaling_governor > cpuinfo_min_freq scaling_max_freq > cpuinfo_transition_latency scaling_min_freq > related_cpus scaling_setspeed > scaling_available_frequencies stats > # cat conservative/down_threshold > 20 > # echo ondemand > scaling_governor Thanks Stephen, There's obviously a difference in our .configs. I have a global conservative directory, ie) /sys/devices/system/cpu/cpufreq/conservative instead of a per-cpu governor file. ie) what are your .config options for CPUFREQ? Mine are: # # CPU Frequency scaling # CONFIG_CPU_FREQ=y CONFIG_CPU_FREQ_GOV_COMMON=y CONFIG_CPU_FREQ_STAT=m CONFIG_CPU_FREQ_STAT_DETAILS=y # CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is not set # CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE is not set # CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND is not set CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE=y CONFIG_CPU_FREQ_GOV_PERFORMANCE=y CONFIG_CPU_FREQ_GOV_POWERSAVE=y CONFIG_CPU_FREQ_GOV_USERSPACE=y CONFIG_CPU_FREQ_GOV_ONDEMAND=y CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y Is there some other config option I have to set? P. > > ====================================================== > [ INFO: possible circular locking dependency detected ] > 3.16.0-rc3-00039-ge1e38f124d87 #47 Not tainted > ------------------------------------------------------- > sh/75 is trying to acquire lock: > (s_active#9){++++..}, at: [] kernfs_remove_by_name_ns+0x3c/0x84 > > but task is already holding lock: > (&policy->rwsem){+++++.}, at: [] store+0x68/0xb8 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (&policy->rwsem){+++++.}: > [] kernfs_fop_open+0x138/0x298 > [] do_dentry_open.isra.12+0x1b0/0x2f0 > [] finish_open+0x20/0x38 > [] do_last.isra.37+0x5ac/0xb68 > [] path_openat+0xb4/0x5d8 > [] do_filp_open+0x2c/0x80 > [] do_sys_open+0x10c/0x1c8 > [] ret_fast_syscall+0x0/0x48 > > -> #0 (s_active#9){++++..}: > [] __kernfs_remove+0x250/0x300 > [] kernfs_remove_by_name_ns+0x3c/0x84 > [] remove_files+0x34/0x78 > [] sysfs_remove_group+0x40/0x98 > [] cpufreq_governor_dbs+0x4c0/0x6ec > [] __cpufreq_governor+0x118/0x200 > [] cpufreq_set_policy+0x158/0x2ac > [] store_scaling_governor+0x6c/0x94 > [] store+0x88/0xb8 > [] sysfs_kf_write+0x4c/0x50 > [] kernfs_fop_write+0xc0/0x180 > [] vfs_write+0xa0/0x1a8 > [] SyS_write+0x40/0x8c > [] ret_fast_syscall+0x0/0x48 > > other info that might help us debug this: > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&policy->rwsem); > lock(s_active#9); > lock(&policy->rwsem); > lock(s_active#9); > > *** DEADLOCK *** > > 6 locks held by sh/75: > #0: (sb_writers#4){.+.+..}, at: [] vfs_write+0x180/0x1a8 > #1: (&of->mutex){+.+...}, at: [] kernfs_fop_write+0x84/0x180 > #2: (s_active#10){.+.+..}, at: [] kernfs_fop_write+0x8c/0x180 > #3: (cpu_hotplug.lock){++++++}, at: [] get_online_cpus+0x38/0x9c > #4: (cpufreq_rwsem){.+.+.+}, at: [] store+0x50/0xb8 > #5: (&policy->rwsem){+++++.}, at: [] store+0x68/0xb8 > > stack backtrace: > CPU: 0 PID: 75 Comm: sh Not tainted 3.16.0-rc3-00039-ge1e38f124d87 #47 > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > [] (show_stack) from [] (dump_stack+0x70/0xbc) > [] (dump_stack) from [] (print_circular_bug+0x280/0x2d4) > [] (print_circular_bug) from [] (__lock_acquire+0x18d0/0x1abc) > [] (__lock_acquire) from [] (lock_acquire+0x9c/0x138) > [] (lock_acquire) from [] (__kernfs_remove+0x250/0x300) > [] (__kernfs_remove) from [] (kernfs_remove_by_name_ns+0x3c/0x84) > [] (kernfs_remove_by_name_ns) from [] (remove_files+0x34/0x78) > [] (remove_files) from [] (sysfs_remove_group+0x40/0x98) > [] (sysfs_remove_group) from [] (cpufreq_governor_dbs+0x4c0/0x6ec) > [] (cpufreq_governor_dbs) from [] (__cpufreq_governor+0x118/0x200) > [] (__cpufreq_governor) from [] (cpufreq_set_policy+0x158/0x2ac) > [] (cpufreq_set_policy) from [] (store_scaling_governor+0x6c/0x94) > [] (store_scaling_governor) from [] (store+0x88/0xb8) > [] (store) from [] (sysfs_kf_write+0x4c/0x50) > [] (sysfs_kf_write) from [] (kernfs_fop_write+0xc0/0x180) > [] (kernfs_fop_write) from [] (vfs_write+0xa0/0x1a8) > [] (vfs_write) from [] (SyS_write+0x40/0x8c) > [] (SyS_write) from [] (ret_fast_syscall+0x0/0x48) > >