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authorFrederic Weisbecker <fweisbec@gmail.com>2008-11-26 00:57:25 +0100
committerIngo Molnar <mingo@elte.hu>2008-11-26 01:59:45 +0100
commit287b6e68ca7209caec40b2f44f837c580a413bae (patch)
treeb0867d75868f6049dc5747bd39fdae2d477dde66 /arch
parentfb52607afcd0629776f1dc9e657647ceae81dd50 (diff)
tracing/function-return-tracer: set a more human readable output
Impact: feature This patch sets a C-like output for the function graph tracing. For this aim, we now call two handler for each function: one on the entry and one other on return. This way we can draw a well-ordered call stack. The pid of the previous trace is loosely stored to be compared against the one of the current trace to see if there were a context switch. Without this little feature, the call tree would seem broken at some locations. We could use the sched_tracer to capture these sched_events but this way of processing is much more simpler. 2 spaces have been chosen for indentation to fit the screen while deep calls. The time of execution in nanosecs is printed just after closed braces, it seems more easy this way to find the corresponding function. If the time was printed as a first column, it would be not so easy to find the corresponding function if it is called on a deep depth. I plan to output the return value but on 32 bits CPU, the return value can be 32 or 64, and its difficult to guess on which case we are. I don't know what would be the better solution on X86-32: only print eax (low-part) or even edx (high-part). Actually it's thee same problem when a function return a 8 bits value, the high part of eax could contain junk values... Here is an example of trace: sys_read() { fget_light() { } 526 vfs_read() { rw_verify_area() { security_file_permission() { cap_file_permission() { } 519 } 1564 } 2640 do_sync_read() { pipe_read() { __might_sleep() { } 511 pipe_wait() { prepare_to_wait() { } 760 deactivate_task() { dequeue_task() { dequeue_task_fair() { dequeue_entity() { update_curr() { update_min_vruntime() { } 504 } 1587 clear_buddies() { } 512 add_cfs_task_weight() { } 519 update_min_vruntime() { } 511 } 5602 dequeue_entity() { update_curr() { update_min_vruntime() { } 496 } 1631 clear_buddies() { } 496 update_min_vruntime() { } 527 } 4580 hrtick_update() { hrtick_start_fair() { } 488 } 1489 } 13700 } 14949 } 16016 msecs_to_jiffies() { } 496 put_prev_task_fair() { } 504 pick_next_task_fair() { } 489 pick_next_task_rt() { } 496 pick_next_task_fair() { } 489 pick_next_task_idle() { } 489 ------------8<---------- thread 4 ------------8<---------- finish_task_switch() { } 1203 do_softirq() { __do_softirq() { __local_bh_disable() { } 669 rcu_process_callbacks() { __rcu_process_callbacks() { cpu_quiet() { rcu_start_batch() { } 503 } 1647 } 3128 __rcu_process_callbacks() { } 542 } 5362 _local_bh_enable() { } 587 } 8880 } 9986 kthread_should_stop() { } 669 deactivate_task() { dequeue_task() { dequeue_task_fair() { dequeue_entity() { update_curr() { calc_delta_mine() { } 511 update_min_vruntime() { } 511 } 2813 Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/ftrace.c32
1 files changed, 21 insertions, 11 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 3595a4c14ab..26b2d92d48b 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -347,7 +347,7 @@ void ftrace_nmi_exit(void)
/* Add a function return address to the trace stack on thread info.*/
static int push_return_trace(unsigned long ret, unsigned long long time,
- unsigned long func)
+ unsigned long func, int *depth)
{
int index;
@@ -365,21 +365,22 @@ static int push_return_trace(unsigned long ret, unsigned long long time,
current->ret_stack[index].ret = ret;
current->ret_stack[index].func = func;
current->ret_stack[index].calltime = time;
+ *depth = index;
return 0;
}
/* Retrieve a function return address to the trace stack on thread info.*/
-static void pop_return_trace(unsigned long *ret, unsigned long long *time,
- unsigned long *func, unsigned long *overrun)
+static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
{
int index;
index = current->curr_ret_stack;
*ret = current->ret_stack[index].ret;
- *func = current->ret_stack[index].func;
- *time = current->ret_stack[index].calltime;
- *overrun = atomic_read(&current->trace_overrun);
+ trace->func = current->ret_stack[index].func;
+ trace->calltime = current->ret_stack[index].calltime;
+ trace->overrun = atomic_read(&current->trace_overrun);
+ trace->depth = index;
current->curr_ret_stack--;
}
@@ -390,12 +391,13 @@ static void pop_return_trace(unsigned long *ret, unsigned long long *time,
unsigned long ftrace_return_to_handler(void)
{
struct ftrace_graph_ret trace;
- pop_return_trace(&trace.ret, &trace.calltime, &trace.func,
- &trace.overrun);
+ unsigned long ret;
+
+ pop_return_trace(&trace, &ret);
trace.rettime = cpu_clock(raw_smp_processor_id());
- ftrace_graph_function(&trace);
+ ftrace_graph_return(&trace);
- return trace.ret;
+ return ret;
}
/*
@@ -407,6 +409,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
unsigned long old;
unsigned long long calltime;
int faulted;
+ struct ftrace_graph_ent trace;
unsigned long return_hooker = (unsigned long)
&return_to_handler;
@@ -452,8 +455,15 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
calltime = cpu_clock(raw_smp_processor_id());
- if (push_return_trace(old, calltime, self_addr) == -EBUSY)
+ if (push_return_trace(old, calltime,
+ self_addr, &trace.depth) == -EBUSY) {
*parent = old;
+ return;
+ }
+
+ trace.func = self_addr;
+ ftrace_graph_entry(&trace);
+
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */