Re: [PATCH 1/2] Adds full stack to critical-section tracing

[Daniel Walker]

On Fri, 2007-08-10 at 08:14 -0600, Gregory Haskins wrote:
> ---
> 
>  include/linux/sched.h  |7 +--
>  kernel/latency_trace.c |   18 +++---
>  2 files changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 8ebb43c..233d26c 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1306,10 +1306,13 @@ struct task_struct {
>  #endif
>  
>  #define MAX_PREEMPT_TRACE 25
> +#define MAX_PREEMPT_TRACE_DEPTH 5
>  
>  #ifdef CONFIG_PREEMPT_TRACE
> - unsigned long preempt_trace_eip[MAX_PREEMPT_TRACE];
> - unsigned long preempt_trace_parent_eip[MAX_PREEMPT_TRACE];
> + struct {
> + struct stack_trace trace;
> + unsigned long  data[MAX_PREEMPT_TRACE_DEPTH];
> + } preempt_trace[MAX_PREEMPT_TRACE];

These changes need some fixing .. The "struct stack_trace"
infrastructure is based on CONFIG_STACKTRACE , so at least you would
want to ifdef your changes on that config options ..

I modified you patch to include the ifdefs,

ftp://source.mvista.com/pub/dwalker/misc/debug-preempt-5-levels-of-stack-frames.patch

The other problem I noticed is that the save_stack_trace(trace); seems
kind of heavy weight to be calling from inside add_preempt_count. If
your only going to a depth of 5 you could potentially use there macros,

#ifdef CONFIG_FRAME_POINTER
# ifndef CONFIG_ARM
#  define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
#  define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
#  define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
#  define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
#  define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
#  define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
# else

Daniel

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Re: [PATCH 1/2] Adds full stack to critical-section tracing

[Daniel Walker]

On Fri, 2007-08-10 at 08:14 -0600, Gregory Haskins wrote:
 ---
 
  include/linux/sched.h  |7 +--
  kernel/latency_trace.c |   18 +++---
  2 files changed, 16 insertions(+), 9 deletions(-)
 
 diff --git a/include/linux/sched.h b/include/linux/sched.h
 index 8ebb43c..233d26c 100644
 --- a/include/linux/sched.h
 +++ b/include/linux/sched.h
 @@ -1306,10 +1306,13 @@ struct task_struct {
  #endif
  
  #define MAX_PREEMPT_TRACE 25
 +#define MAX_PREEMPT_TRACE_DEPTH 5
  
  #ifdef CONFIG_PREEMPT_TRACE
 - unsigned long preempt_trace_eip[MAX_PREEMPT_TRACE];
 - unsigned long preempt_trace_parent_eip[MAX_PREEMPT_TRACE];
 + struct {
 + struct stack_trace trace;
 + unsigned long  data[MAX_PREEMPT_TRACE_DEPTH];
 + } preempt_trace[MAX_PREEMPT_TRACE];

These changes need some fixing .. The struct stack_trace
infrastructure is based on CONFIG_STACKTRACE , so at least you would
want to ifdef your changes on that config options ..

I modified you patch to include the ifdefs,

ftp://source.mvista.com/pub/dwalker/misc/debug-preempt-5-levels-of-stack-frames.patch

The other problem I noticed is that the save_stack_trace(trace); seems
kind of heavy weight to be calling from inside add_preempt_count. If
your only going to a depth of 5 you could potentially use there macros,

#ifdef CONFIG_FRAME_POINTER
# ifndef CONFIG_ARM
#  define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
#  define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
#  define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
#  define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
#  define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
#  define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
# else

Daniel

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[PATCH 1/2] Adds full stack to critical-section tracing

[Gregory Haskins]

---

 include/linux/sched.h  |7 +--
 kernel/latency_trace.c |   18 +++---
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8ebb43c..233d26c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1306,10 +1306,13 @@ struct task_struct {
 #endif
 
 #define MAX_PREEMPT_TRACE 25
+#define MAX_PREEMPT_TRACE_DEPTH 5
 
 #ifdef CONFIG_PREEMPT_TRACE
-   unsigned long preempt_trace_eip[MAX_PREEMPT_TRACE];
-   unsigned long preempt_trace_parent_eip[MAX_PREEMPT_TRACE];
+   struct {
+   struct stack_trace trace;
+   unsigned long  data[MAX_PREEMPT_TRACE_DEPTH];
+   } preempt_trace[MAX_PREEMPT_TRACE];
 #endif
 
 #define MAX_LOCK_STACK MAX_PREEMPT_TRACE
diff --git a/kernel/latency_trace.c b/kernel/latency_trace.c
index 1113744..9b83262 100644
--- a/kernel/latency_trace.c
+++ b/kernel/latency_trace.c
@@ -2049,8 +2049,15 @@ void notrace add_preempt_count(unsigned int val)
if (val <= 10) {
unsigned int idx = preempt_count() & PREEMPT_MASK;
if (idx < MAX_PREEMPT_TRACE) {
-   current->preempt_trace_eip[idx] = eip;
-   current->preempt_trace_parent_eip[idx] = parent_eip;
+   struct stack_trace *trace;
+
+   trace = >preempt_trace[idx].trace;
+   trace->nr_entries = 0;
+   trace->max_entries = MAX_PREEMPT_TRACE_DEPTH;
+   trace->skip = 0;
+   trace->entries = current->preempt_trace[idx].data;
+
+   save_stack_trace(trace);
}
}
 #endif
@@ -2708,11 +2715,8 @@ static void print_preempt_trace(struct task_struct *task)
printk("| %d-level deep critical section nesting:\n", lim);
printk("\n");
for (i = 1; i <= lim; i++) {
-   printk(".. [<%08lx>]  ", task->preempt_trace_eip[i]);
-   print_symbol("%s\n", task->preempt_trace_eip[i]);
-   printk(".[<%08lx>] ..   ( <= ",
-   task->preempt_trace_parent_eip[i]);
-   print_symbol("%s)\n", task->preempt_trace_parent_eip[i]);
+   printk("   Critial Section #%d \n", i);
+   print_stack_trace(>preempt_trace[i].trace, 5);
}
printk("\n");
 }

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[PATCH 1/2] Adds full stack to critical-section tracing

[Gregory Haskins]

---

 include/linux/sched.h  |7 +--
 kernel/latency_trace.c |   18 +++---
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8ebb43c..233d26c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1306,10 +1306,13 @@ struct task_struct {
 #endif
 
 #define MAX_PREEMPT_TRACE 25
+#define MAX_PREEMPT_TRACE_DEPTH 5
 
 #ifdef CONFIG_PREEMPT_TRACE
-   unsigned long preempt_trace_eip[MAX_PREEMPT_TRACE];
-   unsigned long preempt_trace_parent_eip[MAX_PREEMPT_TRACE];
+   struct {
+   struct stack_trace trace;
+   unsigned long  data[MAX_PREEMPT_TRACE_DEPTH];
+   } preempt_trace[MAX_PREEMPT_TRACE];
 #endif
 
 #define MAX_LOCK_STACK MAX_PREEMPT_TRACE
diff --git a/kernel/latency_trace.c b/kernel/latency_trace.c
index 1113744..9b83262 100644
--- a/kernel/latency_trace.c
+++ b/kernel/latency_trace.c
@@ -2049,8 +2049,15 @@ void notrace add_preempt_count(unsigned int val)
if (val = 10) {
unsigned int idx = preempt_count()  PREEMPT_MASK;
if (idx  MAX_PREEMPT_TRACE) {
-   current-preempt_trace_eip[idx] = eip;
-   current-preempt_trace_parent_eip[idx] = parent_eip;
+   struct stack_trace *trace;
+
+   trace = current-preempt_trace[idx].trace;
+   trace-nr_entries = 0;
+   trace-max_entries = MAX_PREEMPT_TRACE_DEPTH;
+   trace-skip = 0;
+   trace-entries = current-preempt_trace[idx].data;
+
+   save_stack_trace(trace);
}
}
 #endif
@@ -2708,11 +2715,8 @@ static void print_preempt_trace(struct task_struct *task)
printk(| %d-level deep critical section nesting:\n, lim);
printk(\n);
for (i = 1; i = lim; i++) {
-   printk(.. [%08lx]  , task-preempt_trace_eip[i]);
-   print_symbol(%s\n, task-preempt_trace_eip[i]);
-   printk(.[%08lx] ..   ( = ,
-   task-preempt_trace_parent_eip[i]);
-   print_symbol(%s)\n, task-preempt_trace_parent_eip[i]);
+   printk(   Critial Section #%d \n, i);
+   print_stack_trace(task-preempt_trace[i].trace, 5);
}
printk(\n);
 }

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