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tracing: Have dynamic size event stack traces

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Currently the stack trace per event in ftace is only 8 frames.
This can be quite limiting and sometimes useless. Especially when
the "ignore frames" is wrong and we also use up stack frames for
the event processing itself.

Change this to be dynamic by adding a percpu buffer that we can
write a large stack frame into and then copy into the ring buffer.

For interrupts and NMIs that come in while another event is being
process, will only get to use the 8 frame stack. That should be enough
as the task that it interrupted will have the full stack frame anyway.

Requested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2011-07-14 16:36:53 -04:00 • committed by Steven Rostedt
parent 259032bfe3
commit 4a9bd3f134
4 changed files with 89 additions and 20 deletions
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11
kernel/trace/trace_output.c
View file

@ -1107,19 +1107,20 @@ static enum print_line_t trace_stack_print(struct trace_iterator *iter,
{
struct stack_entry *field;
struct trace_seq *s = &iter->seq;
int i;
unsigned long *p;
unsigned long *end;
trace_assign_type(field, iter->ent);
end = (unsigned long *)((long)iter->ent + iter->ent_size);
if (!trace_seq_puts(s, "<stack trace>\n"))
goto partial;
for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
if (!field->caller[i] || (field->caller[i] == ULONG_MAX))
break;
for (p = field->caller; p && *p != ULONG_MAX && p < end; p++) {
if (!trace_seq_puts(s, " => "))
goto partial;
if (!seq_print_ip_sym(s, field->caller[i], flags))
if (!seq_print_ip_sym(s, *p, flags))
goto partial;
if (!trace_seq_puts(s, "\n"))
goto partial;