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Date: Tue, 22 Jan 2008 17:25:38 +0100 From: Peter Zijlstra <a.p.zijlstra@...llo.nl> To: Dave Young <hidave.darkstar@...il.com> Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> Subject: [PATCH] sched: don't take a mutex from interrupt context On Tue, 2008-01-22 at 10:36 +0800, Dave Young wrote: > While try to trigger bug 9778, press ctrl+alt+sysrq +w, the following warnings appeared: > > usb0: unregister 'cdc_ether' usb-0000:00:1d.7-1.3, CDC Ethernet Device > unregister_netdevice: waiting for usb0 to become free. Usage count = 1 > SysRq : Show Blocked State > task PC stack pid father > Sched Debug Version: v0.07, 2.6.24-rc8-mm1 #5 > now at 2660467.699238 msecs > .sysctl_sched_latency : 40.000000 > .sysctl_sched_min_granularity : 8.000000 > .sysctl_sched_wakeup_granularity : 20.000000 > .sysctl_sched_batch_wakeup_granularity : 20.000000 > .sysctl_sched_child_runs_first : 0.000001 > .sysctl_sched_features : 39 > > cpu#0, 2793.192 MHz > .nr_running : 2 > .load : 4096 > .nr_switches : 1627754 > .nr_load_updates : 241563 > .nr_uninterruptible : 4294967012 > .jiffies : 708140 > .next_balance : 0.708327 > .curr->pid : 0 > .clock : 2656959.965268 > .idle_clock : 0.000000 > .prev_clock_raw : 2674890.031768 > .clock_warps : 0 > .clock_overflows : 5805 > .clock_underflows : 127079 > .clock_deep_idle_events : 2 > .clock_max_delta : 671.628710 > .cpu_load[0] : 0 > .cpu_load[1] : 0 > .cpu_load[2] : 6 > .cpu_load[3] : 48 > .cpu_load[4] : 85 > > cfs_rq > .exec_clock : 0.000000 > .MIN_vruntime : 180379.753201 > .min_vruntime : 180379.753201 > .max_vruntime : 180379.753201 > .spread : 0.000000 > .spread0 : 0.000000 > .nr_running : 1 > .load : 4096 > .nr_spread_over : 0 > ------------[ cut here ]------------ > WARNING: at kernel/mutex.c:134 mutex_lock_nested+0x277/0x290() > Modules linked in: cdc_ether usbnet snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss snd_mixer_oss eeprom e100 psmouse snd_hda_intel snd_pcm intel_agp btusb snd_timer rtc_cmos bluetooth sg rtc_core 3c59x evdev agpgart snd serio_raw button thermal processor soundcore rtc_lib snd_page_alloc i2c_i801 pcspkr dcdbas > Pid: 0, comm: swapper Not tainted 2.6.24-rc8-mm1 #5 > [<c0132100>] ? printk+0x0/0x20 > [<c0131834>] warn_on_slowpath+0x54/0x80 > [<c043641e>] ? _spin_unlock_irqrestore+0x5e/0x70 > [<c0132791>] ? release_console_sem+0xd1/0xe0 > [<c0132428>] ? vprintk+0x308/0x320 > [<c0153241>] ? put_lock_stats+0x21/0x30 > [<c01532b0>] ? lock_release_holdtime+0x60/0x80 > [<c0126b07>] ? print_cfs_rq+0x117/0x500 > [<c0156b87>] ? __lock_release+0x47/0x70 > [<c0126b07>] ? print_cfs_rq+0x117/0x500 > [<c0132118>] ? printk+0x18/0x20 > [<c0434757>] mutex_lock_nested+0x277/0x290 > [<c0132428>] ? vprintk+0x308/0x320 > [<c0124f60>] ? print_cfs_stats+0x30/0xb0 > [<c0124f60>] print_cfs_stats+0x30/0xb0 > [<c012770c>] print_cpu+0x81c/0x830 > [<c012794a>] sched_debug_show+0x22a/0x430 > [<c0127b5c>] sysrq_sched_debug_show+0xc/0x10 > [<c012bb06>] show_state_filter+0x86/0xb0 > [<c02c95cd>] sysrq_handle_showstate_blocked+0xd/0x10 > [<c02c97a9>] __handle_sysrq+0x89/0x120 > [<c02c9873>] handle_sysrq+0x33/0x40 > [<c02c39ae>] kbd_keycode+0x39e/0x480 > [<c013b320>] ? __mod_timer+0xa0/0xb0 > [<c02c3b7a>] kbd_event+0xea/0x100 > [<c0386d0c>] input_pass_event+0xec/0x100 > [<c0386c20>] ? input_pass_event+0x0/0x100 > [<c013b3b6>] ? mod_timer+0x26/0x40 > [<c0386ef2>] input_handle_event+0xb2/0x2b0 > [<c038714f>] input_event+0x5f/0x80 > [<c03a1e2f>] hidinput_hid_event+0xef/0x390 > [<c039f410>] ? hid_input_field+0x40/0x340 > [<c039f3a3>] hid_process_event+0x63/0x90 > [<c039f695>] hid_input_field+0x2c5/0x340 > [<c039fc66>] hid_input_report+0x106/0x260 > [<c015322d>] ? put_lock_stats+0xd/0x30 > [<c01532b0>] ? lock_release_holdtime+0x60/0x80 > [<c03a44e1>] hid_irq_in+0x181/0x190 > [<c03816fa>] ? uhci_giveback_urb+0x8a/0x160 > [<c0368b31>] usb_hcd_giveback_urb+0x41/0xa0 > [<c0381707>] uhci_giveback_urb+0x97/0x160 > [<c0381840>] uhci_scan_qh+0x70/0x1c0 > [<c0381b0b>] uhci_scan_schedule+0x8b/0x130 > [<c03828f5>] uhci_irq+0xb5/0x150 > [<c0156b87>] ? __lock_release+0x47/0x70 > [<c0368ec4>] usb_hcd_irq+0x24/0x60 > [<c0164fd8>] handle_IRQ_event+0x28/0x60 > [<c016626e>] handle_fasteoi_irq+0x6e/0xd0 > [<c01078ac>] do_IRQ+0x3c/0x80 > [<c0151d2c>] ? tick_nohz_stop_sched_tick+0x25c/0x350 > [<c01059ca>] common_interrupt+0x2e/0x34 > [<c0103390>] ? mwait_idle_with_hints+0x40/0x50 > [<c01033a0>] ? mwait_idle+0x0/0x20 > [<c01033b2>] mwait_idle+0x12/0x20 > [<c0103141>] cpu_idle+0x61/0x110 > [<c04333bd>] rest_init+0x5d/0x60 > [<c05a47fa>] start_kernel+0x1fa/0x260 > [<c05a4190>] ? unknown_bootoption+0x0/0x130 > ======================= > ---[ end trace bc131943b9b4ac4c ]--- > -- --- Subject: sched: don't take a mutex from interrupt context print_cfs_stats is callable from interrupt context (sysrq), hence it should not take mutexes. Change it to use RCU since the task group data is RCU freed anyway. Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl> --- kernel/sched_fair.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -1428,9 +1428,9 @@ static void print_cfs_stats(struct seq_f #ifdef CONFIG_FAIR_GROUP_SCHED print_cfs_rq(m, cpu, &cpu_rq(cpu)->cfs); #endif - lock_task_group_list(); + rcu_read_lock(); for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) print_cfs_rq(m, cpu, cfs_rq); - unlock_task_group_list(); + rcu_read_unlock(); } #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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