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fgraph: Have set_graph_notrace only affect function_graph tracer

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In order to make the function graph infrastructure more generic, there can
not be code specific for the function_graph tracer in the generic code. This
includes the set_graph_notrace logic, that stops all graph calls when a
function in the set_graph_notrace is hit.

By using the trace_recursion mask, we can use a bit in the current
task_struct to implement the notrace code, and move the logic out of
fgraph.c and into trace_functions_graph.c and keeps it affecting only the
tracer and not all call graph callbacks.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2018-11-14 13:14:58 -05:00
parent d864a3ca88
commit 9cd2992f2d
3 changed files with 29 additions and 21 deletions
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21
kernel/trace/fgraph.c
View File

@ -64,30 +64,9 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
return -EBUSY;
}
/*
* The curr_ret_stack is an index to ftrace return stack of
* current task. Its value should be in [0, FTRACE_RETFUNC_
* DEPTH) when the function graph tracer is used. To support
* filtering out specific functions, it makes the index
* negative by subtracting huge value (FTRACE_NOTRACE_DEPTH)
* so when it sees a negative index the ftrace will ignore
* the record. And the index gets recovered when returning
* from the filtered function by adding the FTRACE_NOTRACE_
* DEPTH and then it'll continue to record functions normally.
*
* The curr_ret_stack is initialized to -1 and get increased
* in this function. So it can be less than -1 only if it was
* filtered out via ftrace_graph_notrace_addr() which can be
* set from set_graph_notrace file in tracefs by user.
*/
if (current->curr_ret_stack < -1)
return -EBUSY;
calltime = trace_clock_local();
index = ++current->curr_ret_stack;
if (ftrace_graph_notrace_addr(func))
current->curr_ret_stack -= FTRACE_NOTRACE_DEPTH;
barrier();
current->ret_stack[index].ret = ret;
current->ret_stack[index].func = func;

7
kernel/trace/trace.h
View File

@ -534,6 +534,13 @@ enum {
TRACE_GRAPH_DEPTH_START_BIT,
TRACE_GRAPH_DEPTH_END_BIT,
/*
* To implement set_graph_notrace, if this bit is set, we ignore
* function graph tracing of called functions, until the return
* function is called to clear it.
*/
TRACE_GRAPH_NOTRACE_BIT,
};
#define trace_recursion_set(bit) do { (current)->trace_recursion |= (1<<(bit)); } while (0)

22
kernel/trace/trace_functions_graph.c
View File

@ -188,6 +188,18 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
int cpu;
int pc;
if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT))
return 0;
if (ftrace_graph_notrace_addr(trace->func)) {
trace_recursion_set(TRACE_GRAPH_NOTRACE_BIT);
/*
* Need to return 1 to have the return called
* that will clear the NOTRACE bit.
*/
return 1;
}
if (!ftrace_trace_task(tr))
return 0;
@ -290,6 +302,11 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
ftrace_graph_addr_finish(trace);
if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
return;
}
local_irq_save(flags);
cpu = raw_smp_processor_id();
data = per_cpu_ptr(tr->trace_buffer.data, cpu);
@ -315,6 +332,11 @@ static void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
{
ftrace_graph_addr_finish(trace);
if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
return;
}
if (tracing_thresh &&
(trace->rettime - trace->calltime < tracing_thresh))
return;