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Date: Tue, 15 Jul 2014 13:27:19 +0400
From: Stanislav Fomichev <stfomichev@...dex-team.ru>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: fweisbec@...il.com, mingo@...hat.com, jovi.zhangwei@...wei.com,
namhyung.kim@....com, tom.zanussi@...ux.intel.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] tracing: let user specify tracing_thresh after
selecting function_graph
Hi Steven,
Did you have some spare time to check why I'm getting triple fault with the
jump labels inside function tracers? Or will you just pull my another
patch without them?
On Thu, Jun 05, 2014 at 11:38:39AM +0400, Stanislav Fomichev wrote:
> > You mean inside the function tracers. I could envision problems with
> > that, but I don't know exactly what would cause those problems. Have
> > patches to show? You may have done something unrelated that caused the
> > issue.
> Maybe I'm using jump labels incorrectly, patch attached below.
> And, when I set tracing_thresh after selecting function_graph, I get:
>
> [ 42.337679] PANIC: double fault, error_code: 0x0
> [ 42.337357] PANIC: double fault, error_code: 0x0
> [ 42.337357] CPU: 1 PID: 1388 Comm: bash Not tainted 3.15.0-upstream #33
> [ 42.337357] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> [ 42.337357] task: ffff88001f5b3aa0 ti: ffff8800185d4000 task.ti: ffff8800185d4000
> [ 42.337357] RIP: 0010:[<ffffffff811006d4>] [<ffffffff811006d4>] trace_buffer_lock_reserve+0x4/0x80
> [ 42.337357] RSP: 0000:ffff88001f7ffff0 EFLAGS: 00010086
> [ 42.337357] RAX: 0000000000000000 RBX: ffff88001e409d80 RCX: 0000000000000046
> [ 42.337357] RDX: 0000000000000018 RSI: 000000000000000b RDI: ffff88001e409d80
> [ 42.337357] RBP: ffff88001f800070 R08: 0000000000000000 R09: 0000000000000554
> [ 42.337357] R10: 0000000000000000 R11: 0000000000000013 R12: ffffffff81054e30
> [ 42.337357] R13: 0000000000000000 R14: 0000000000000286 R15: 0000000000000003
> [ 42.337357] FS: 00007f5a6cd83700(0000) GS:ffff88001fd00000(0000) knlGS:0000000000000000
> [ 42.337357] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 42.337357] CR2: ffff88001f7fffe8 CR3: 0000000000e20000 CR4: 00000000000006e0
> [ 42.337357] Stack:
> [ 42.337357] ffffffffa0010f50 ffffffffa0011170
> [ 42.337357] Call Trace:
> [ 42.337357] <UNK>
> [ 42.337357] Code: 02 00 00 48 63 ca 89 14 bd a0 4b ed 81 89 34 8d 60 43 eb 81 89 35 bd 44 dd 00 e9 45 ff ff ff 0f 1f 84 00 00 00 00 00 48 83 ec 28 <48> 89 1c 24 89 f3 48 8
> 9 d6 48 89 6c 24 08 4c 89 64 24 10 48 89
> [ 42.337357] Kernel panic - not syncing: Machine halted.
> [ 42.337357] CPU: 1 PID: 1388 Comm: bash Not tainted 3.15.0-upstream #33
> [ 42.337357] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> [ 42.337357] 0000000000000000 ffffffff810184f5 ffffffff816673d3 ffffffff8193437f
> [ 42.337357] ffffffff8166223e 0000000000000000 ffffffff00000008 ffff88001fd06f28
> [ 42.337357] ffff88001fd06ec8 00000000000012cc 0000000000000082 0000000000000082
> [ 42.337357] Call Trace:
> [ 42.337357] <#DF> [<ffffffff810184f5>] ? show_stack+0x5/0x50
> [ 42.337357] [<ffffffff816673d3>] ? dump_stack+0x41/0x51
> [ 42.337357] [<ffffffff8166223e>] ? panic+0xca/0x1e7
> [ 42.337357] [<ffffffff8104d89d>] ? df_debug+0x2d/0x30
> [ 42.337357] [<ffffffff81015518>] ? do_double_fault+0x58/0x80
> [ 42.337357] [<ffffffff81054e30>] ? perf_trace_x86_exceptions+0x130/0x130
> [ 42.337357] [<ffffffff81670d08>] ? double_fault+0x28/0x30
> [ 42.337357] [<ffffffff81054e30>] ? perf_trace_x86_exceptions+0x130/0x130
> [ 42.337357] [<ffffffff811006d4>] ? trace_buffer_lock_reserve+0x4/0x80
> [ 42.337679] <<EOE>> <UNK>
> [ 42.337679] CPU: 0 PID: 1386 Comm: sshd Not tainted 3.15.0-upstream #33
> [ 42.337679] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> [ 42.337679] task: ffff88001f5b29e0 ti: ffff88001849c000 task.ti: ffff88001849c000
> [ 42.337679] RIP: 0010:[<ffffffff811006d4>] [<ffffffff811006d4>] trace_buffer_lock_reserve+0x4/0x80
> [ 42.337679] RSP: 0018:ffff88001f7ffff0 EFLAGS: 00010086
> [ 42.337679] RAX: 0000000000000000 RBX: ffff88001e409d80 RCX: 0000000000000046
> [ 42.337679] RDX: 0000000000000018 RSI: 000000000000000b RDI: ffff88001e409d80
> [ 42.337679] RBP: ffff88001f800070 R08: 0000000000010000 R09: 00000000000000f4
> [ 42.337679] R10: 0000000000000000 R11: 0000000000000010 R12: ffffffff81054e30
> [ 42.337679] R13: 0000000000000000 R14: ffff88001fc0dff8 R15: 0000000000000003
> [ 42.337679] FS: 00007f2b388a87c0(0000) GS:ffff88001fc00000(0000) knlGS:0000000000000000
> [ 42.337679] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 42.337679] CR2: ffff88001f7fffe8 CR3: 00000000179ea000 CR4: 00000000000006f0
> [ 42.337679] Stack:
> [ 42.337679] ffffffffa0010f50 ffffffffa0011170
> [ 42.337679] Call Trace:
> [ 42.337679] <UNK>
> [ 42.337679] Code: 02 00 00 48 63 ca 89 14 bd a0 4b ed 81 89 34 8d 60 43 eb 81 89 35 bd 44 dd 00 e9 45 ff ff ff 0f 1f 84 00 00 00 00 00 48 83 ec 28 <48> 89 1c 24 89 f3 48 89 d6 48 89 6c 24 08 4c 89 64 24 10 48 89
> [ 42.337357] Shutting down cpus with NMI
> [ 42.337357] Kernel Offset: 0x0 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffff9fffffff)
> [ 42.337357] ---[ end Kernel panic - not syncing: Machine halted.
>
> --
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 737b0efa1a62..0b58d2ff94f6 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -750,6 +750,14 @@ static int __init set_buf_size(char *str)
> }
> __setup("trace_buf_size=", set_buf_size);
>
> +static void update_tracing_thresh_enabled(void)
> +{
> + if (tracing_thresh && !static_key_enabled(&__tracing_thresh_enabled))
> + static_key_slow_inc(&__tracing_thresh_enabled);
> + if (!tracing_thresh && static_key_enabled(&__tracing_thresh_enabled))
> + static_key_slow_dec(&__tracing_thresh_enabled);
> +}
> +
> static int __init set_tracing_thresh(char *str)
> {
> unsigned long threshold;
> @@ -761,6 +769,7 @@ static int __init set_tracing_thresh(char *str)
> if (ret < 0)
> return 0;
> tracing_thresh = threshold * 1000;
> + update_tracing_thresh_enabled();
> return 1;
> }
> __setup("tracing_thresh=", set_tracing_thresh);
> @@ -980,6 +989,7 @@ static arch_spinlock_t ftrace_max_lock =
> (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
>
> unsigned long __read_mostly tracing_thresh;
> +struct static_key __tracing_thresh_enabled;
>
> #ifdef CONFIG_TRACER_MAX_TRACE
> unsigned long __read_mostly tracing_max_latency;
> @@ -4104,6 +4114,7 @@ tracing_max_lat_write(struct file *filp, const char __user *ubuf,
> return ret;
>
> *ptr = val * 1000;
> + update_tracing_thresh_enabled();
>
> return cnt;
> }
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 2e29d7ba5a52..ab32c1f33917 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -606,6 +606,12 @@ extern cpumask_var_t __read_mostly tracing_buffer_mask;
> extern unsigned long nsecs_to_usecs(unsigned long nsecs);
>
> extern unsigned long tracing_thresh;
> +extern struct static_key __tracing_thresh_enabled;
> +
> +static inline bool tracing_thresh_enabled(void)
> +{
> + return static_key_false(&__tracing_thresh_enabled);
> +}
>
> #ifdef CONFIG_TRACER_MAX_TRACE
> extern unsigned long tracing_max_latency;
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index deff11200261..0a893120c05a 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -332,7 +332,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
>
> int trace_graph_thresh_entry(struct ftrace_graph_ent *trace)
> {
> - if (tracing_thresh)
> + if (tracing_thresh_enabled())
> return 1;
> else
> return trace_graph_entry(trace);
> @@ -421,7 +421,7 @@ void set_graph_array(struct trace_array *tr)
>
> void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
> {
> - if (tracing_thresh &&
> + if (tracing_thresh_enabled() &&
> (trace->rettime - trace->calltime < tracing_thresh))
> return;
> else
> @@ -433,12 +433,8 @@ static int graph_trace_init(struct trace_array *tr)
> int ret;
>
> set_graph_array(tr);
> - if (tracing_thresh)
> - ret = register_ftrace_graph(&trace_graph_thresh_return,
> - &trace_graph_thresh_entry);
> - else
> - ret = register_ftrace_graph(&trace_graph_return,
> - &trace_graph_entry);
> + ret = register_ftrace_graph(&trace_graph_thresh_return,
> + &trace_graph_thresh_entry);
> if (ret)
> return ret;
> tracing_start_cmdline_record();
--
Станислав Фомичев
http://staff/stfomichev
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