Re: [PATCHv2] tracing: let user specify tracing_thresh after selecting function_graph
From: Stanislav Fomichev
Date: Thu Jun 05 2014 - 03:49:55 EST
> 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();
--
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