Date:	Mon, 30 Dec 2013 17:06:02 +0800
From:	Weng Meiling <wengmeiling.weng@...wei.com>
To:	Robert Richter <rric@...nel.org>, <oprofile-list@...ts.sf.net>,
	<linux-kernel@...r.kernel.org>
CC:	Li Zefan <lizefan@...wei.com>, <wangnan0@...wei.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	Huang Qiang <h.huangqiang@...wei.com>
Subject: Re: [PATCH] oprofile: check whether oprofile perf enabled in op_overflow_handler()

Hi Robert,
What do you think about this patch?

On 2013/12/20 15:49, Weng Meiling wrote:
> 
> From: Weng Meiling <wengmeiling.weng@...wei.com>
> 
> There is a situation event is triggered before oprofile_perf_start() finish.
> Because the event is still not stored in per_cpu(perf_events, cpu)[event],
> op_overflow_handler() will print the warning. During the time, if unregistered
> event is triggered again, the cpu will print again. This may make cpu keeping
> on printing and trigger softlockup. So check whether events register finished
> in op_overflow_handler().
> 
> The problem was once triggered on kernel 2.6.34, the main information:
> <3>BUG: soft lockup - CPU#0 stuck for 60005ms! [opcontrol:8673]
> 
> Pid: 8673, comm:            opcontrol
> =====================SOFTLOCKUP INFO BEGIN=======================
> [CPU#0] the task [opcontrol] is not waiting for a lock,maybe a delay or deadcricle!
> <6>opcontrol     R<c> running  <c>    0  8673   7603 0x00000002
> locked:
> bf0e1928   mutex            0  [<bf0de0d8>] oprofile_start+0x10/0x68 [oprofile]
> bf0e1a24   mutex            0  [<bf0e07f0>] op_arm_start+0x10/0x48 [oprofile]
> c0628020   &ctx->mutex      0  [<c00af85c>] perf_event_create_kernel_counter+0xa4/0x14c
> [<c00362b8>] (unwind_backtrace+0x0/0x164) from [<c0031db4>] (show_stack+0x10/0x14)
> [<c0031db4>] (show_stack+0x10/0x14) from [<c008d964>] (show_lock_info+0x9c/0x168)
> [<c008d964>] (show_lock_info+0x9c/0x168) from [<c008dbf4>] (softlockup_tick+0x1c4/0x234)
> [<c008dbf4>] (softlockup_tick+0x1c4/0x234) from [<c0066d58>] (update_process_times+0x2c/0x50)
> [<c0066d58>] (update_process_times+0x2c/0x50) from [<c00811cc>] (tick_sched_timer+0x268/0x2c4)
> [<c00811cc>] (tick_sched_timer+0x268/0x2c4) from [<c0077340>] (__run_hrtimer+0x158/0x25c)
> [<c0077340>] (__run_hrtimer+0x158/0x25c) from [<c0077e08>] (hrtimer_interrupt+0x13c/0x2f8)
> [<c0077e08>] (hrtimer_interrupt+0x13c/0x2f8) from [<c003f82c>] (timer64_timer_interrupt+0x20/0x2c)
> [<c003f82c>] (timer64_timer_interrupt+0x20/0x2c) from [<c008e54c>] (handle_IRQ_event+0x144/0x2ec)
> [<c008e54c>] (handle_IRQ_event+0x144/0x2ec) from [<c00900dc>] (handle_level_irq+0xc0/0x13c)
> [<c00900dc>] (handle_level_irq+0xc0/0x13c) from [<c002b080>] (asm_do_IRQ+0x80/0xbc)
> [<c002b080>] (asm_do_IRQ+0x80/0xbc) from [<c0274b8c>] (__irq_svc+0x4c/0xe4)
> Exception stack(0xc4099db8 to 0xc4099e00)
> 9da0:                                                       c0357538 00000000
> 9dc0: 00000000 c0380cc0 c4098000 00000202 00000028 c4098000 3fca9fbc c4098000
> 9de0: c0028b08 00000000 c4098000 c4099e00 c005eb50 c005e544 20000113 ffffffff
> [<c0274b8c>] (__irq_svc+0x4c/0xe4) from [<c005e544>] (__do_softirq+0x64/0x25c)
> [<c005e544>] (__do_softirq+0x64/0x25c) from [<c005eb50>] (irq_exit+0x48/0x5c)
> [<c005eb50>] (irq_exit+0x48/0x5c) from [<c002b084>] (asm_do_IRQ+0x84/0xbc)
> [<c002b084>] (asm_do_IRQ+0x84/0xbc) from [<c0274b8c>] (__irq_svc+0x4c/0xe4)
> Exception stack(0xc4099e58 to 0xc4099ea0)
> 9e40:                                                       c0628010 20000093
> 9e60: 00000001 00000000 00000000 60000013 c00aff24 cc4f6c00 00000001 c4098000
> 9e80: 00000000 00000000 00000000 c4099ea0 c0084fa0 c0084fa4 60000013 ffffffff
> [<c0274b8c>] (__irq_svc+0x4c/0xe4) from [<c0084fa4>] (smp_call_function_single+0xc0/0x1d8)
> [<c0084fa4>] (smp_call_function_single+0xc0/0x1d8) from [<c00af86c>] (perf_event_create_kernel_counter+0xb4/0x14c)
> [<c00af86c>] (perf_event_create_kernel_counter+0xb4/0x14c) from [<bf0e0700>] (op_perf_start+0x54/0xf0 [oprofile])
> [<bf0e0700>] (op_perf_start+0x54/0xf0 [oprofile]) from [<bf0e0800>] (op_arm_start+0x20/0x48 [oprofile])
> [<bf0e0800>] (op_arm_start+0x20/0x48 [oprofile]) from [<bf0de100>] (oprofile_start+0x38/0x68 [oprofile])
> [<bf0de100>] (oprofile_start+0x38/0x68 [oprofile]) from [<bf0dfac0>] (enable_write+0x34/0x54 [oprofile])
> [<bf0dfac0>] (enable_write+0x34/0x54 [oprofile]) from [<c00e5368>] (vfs_write+0xa8/0x150)
> [<c00e5368>] (vfs_write+0xa8/0x150) from [<c00e5698>] (sys_write+0x3c/0x100)
> [<c00e5698>] (sys_write+0x3c/0x100) from [<c002c500>] (ret_fast_syscall+0x0/0x30)
> =====================SOFTLOCKUP INFO END=========================
> <0>Kernel panic - not syncing: softlockup: hung tasks
> 
> Cc: <stable@...r.kernel.org> # 2.6.34+
> Signed-off-by: Weng Meiling <wengmeiling.weng@...wei.com>
> ---
>  drivers/oprofile/oprofile_perf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/oprofile/oprofile_perf.c b/drivers/oprofile/oprofile_perf.c
> index d5b2732..a9e5761 100644
> --- a/drivers/oprofile/oprofile_perf.c
> +++ b/drivers/oprofile/oprofile_perf.c
> @@ -38,6 +38,9 @@ static void op_overflow_handler(struct perf_event *event,
>  	int id;
>  	u32 cpu = smp_processor_id();
> 
> +	if (!oprofile_perf_enabled)
> +		return;
> +
>  	for (id = 0; id < num_counters; ++id)
>  		if (per_cpu(perf_events, cpu)[id] == event)
>  			break;
> 


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