[patch V3 23/29] tracing: Simplify stack trace retrieval

Thomas Gleixner
2019-04-25T10:00:33Z

Replace the indirection through struct stack_trace by using the storage
array based interfaces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 40 +++++++++++++---------------------------
1 file changed, 13 insertions(+), 27 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2774,22 +2774,18 @@ static void __ftrace_trace_stack(struct
{
struct trace_event_call *call = &event_kernel_stack;
struct ring_buffer_event *event;
+ unsigned int size, nr_entries;
struct ftrace_stack *fstack;
struct stack_entry *entry;
- struct stack_trace trace;
- int size = FTRACE_KSTACK_ENTRIES;
int stackidx;

- trace.nr_entries = 0;
- trace.skip = skip;
-
/*
* Add one, for this function and the call to save_stack_trace()
* If regs is set, then these functions will not be in the way.
*/
#ifndef CONFIG_UNWINDER_ORC
if (!regs)
- trace.skip++;
+ skip++;
#endif

/*
@@ -2816,28 +2812,24 @@ static void __ftrace_trace_stack(struct
barrier();

fstack = this_cpu_ptr(ftrace_stacks.stacks) + (stackidx - 1);
- trace.entries = fstack->calls;
- trace.max_entries = FTRACE_KSTACK_ENTRIES;
-
- if (regs)
- save_stack_trace_regs(regs, &trace);
- else
- save_stack_trace(&trace);
-
- if (trace.nr_entries > size)
- size = trace.nr_entries;
+ size = ARRAY_SIZE(fstack->calls);

- size *= sizeof(unsigned long);
+ if (regs) {
+ nr_entries = stack_trace_save_regs(regs, fstack->calls,
+ size, skip);
+ } else {
+ nr_entries = stack_trace_save(fstack->calls, size, skip);
+ }

+ size = nr_entries * sizeof(unsigned long);
event = __trace_buffer_lock_reserve(buffer, TRACE_STACK,
sizeof(*entry) + size, flags, pc);
if (!event)
goto out;
entry = ring_buffer_event_data(event);

- memcpy(&entry->caller, trace.entries, size);
-
- entry->size = trace.nr_entries;
+ memcpy(&entry->caller, fstack->calls, size);
+ entry->size = nr_entries;

if (!call_filter_check_discard(call, entry, buffer, event))
__buffer_unlock_commit(buffer, event);
@@ -2916,7 +2908,6 @@ ftrace_trace_userstack(struct ring_buffe
struct trace_event_call *call = &event_user_stack;
struct ring_buffer_event *event;
struct userstack_entry *entry;
- struct stack_trace trace;

if (!(global_trace.trace_flags & TRACE_ITER_USERSTACKTRACE))
return;
@@ -2947,12 +2938,7 @@ ftrace_trace_userstack(struct ring_buffe
entry->tgid = current->tgid;
memset(&entry->caller, 0, sizeof(entry->caller));

- trace.nr_entries = 0;
- trace.max_entries = FTRACE_STACK_ENTRIES;
- trace.skip = 0;
- trace.entries = entry->caller;
-
- save_stack_trace_user(&trace);
+ stack_trace_save_user(entry->caller, FTRACE_STACK_ENTRIES);
if (!call_filter_check_discard(call, entry, buffer, event))
__buffer_unlock_commit(buffer, event);