static void
function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *pt_regs);
-static struct ftrace_ops trace_ops;
-static struct ftrace_ops trace_stack_ops;
static struct tracer_flags func_flags;
/* Our option */
static int function_trace_init(struct trace_array *tr)
{
- struct ftrace_ops *ops;
-
- if (tr->flags & TRACE_ARRAY_FL_GLOBAL) {
- /* There's only one global tr */
- if (!trace_ops.private) {
- trace_ops.private = tr;
- trace_stack_ops.private = tr;
- }
+ ftrace_func_t func;
- if (func_flags.val & TRACE_FUNC_OPT_STACK)
- ops = &trace_stack_ops;
- else
- ops = &trace_ops;
- tr->ops = ops;
- } else if (!tr->ops) {
- /*
- * Instance trace_arrays get their ops allocated
- * at instance creation. Unless it failed
- * the allocation.
- */
+ /*
+ * Instance trace_arrays get their ops allocated
+ * at instance creation. Unless it failed
+ * the allocation.
+ */
+ if (!tr->ops)
return -ENOMEM;
- }
+
+ /* Currently only the global instance can do stack tracing */
+ if (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
+ func_flags.val & TRACE_FUNC_OPT_STACK)
+ func = function_stack_trace_call;
+ else
+ func = function_trace_call;
+
+ ftrace_init_array_ops(tr, func);
tr->trace_buffer.cpu = get_cpu();
put_cpu();
{
tracing_stop_function_trace(tr);
tracing_stop_cmdline_record();
+ ftrace_reset_array_ops(tr);
}
static void function_trace_start(struct trace_array *tr)
local_irq_restore(flags);
}
-static struct ftrace_ops trace_ops __read_mostly =
-{
- .func = function_trace_call,
- .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
-};
-
-static struct ftrace_ops trace_stack_ops __read_mostly =
-{
- .func = function_stack_trace_call,
- .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
-};
-
static struct tracer_opt func_opts[] = {
#ifdef CONFIG_STACKTRACE
{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
unregister_ftrace_function(tr->ops);
if (set) {
- tr->ops = &trace_stack_ops;
+ tr->ops->func = function_stack_trace_call;
register_ftrace_function(tr->ops);
} else {
- tr->ops = &trace_ops;
+ tr->ops->func = function_trace_call;
register_ftrace_function(tr->ops);
}
.init = function_trace_init,
.reset = function_trace_reset,
.start = function_trace_start,
- .wait_pipe = poll_wait_pipe,
.flags = &func_flags,
.set_flag = func_set_flag,
.allow_instances = true,
};
#ifdef CONFIG_DYNAMIC_FTRACE
-static int update_count(void **data)
+static void update_traceon_count(void **data, bool on)
{
- unsigned long *count = (long *)data;
+ long *count = (long *)data;
+ long old_count = *count;
- if (!*count)
- return 0;
+ /*
+ * Tracing gets disabled (or enabled) once per count.
+ * This function can be called at the same time on multiple CPUs.
+ * It is fine if both disable (or enable) tracing, as disabling
+ * (or enabling) the second time doesn't do anything as the
+ * state of the tracer is already disabled (or enabled).
+ * What needs to be synchronized in this case is that the count
+ * only gets decremented once, even if the tracer is disabled
+ * (or enabled) twice, as the second one is really a nop.
+ *
+ * The memory barriers guarantee that we only decrement the
+ * counter once. First the count is read to a local variable
+ * and a read barrier is used to make sure that it is loaded
+ * before checking if the tracer is in the state we want.
+ * If the tracer is not in the state we want, then the count
+ * is guaranteed to be the old count.
+ *
+ * Next the tracer is set to the state we want (disabled or enabled)
+ * then a write memory barrier is used to make sure that
+ * the new state is visible before changing the counter by
+ * one minus the old counter. This guarantees that another CPU
+ * executing this code will see the new state before seeing
+ * the new counter value, and would not do anything if the new
+ * counter is seen.
+ *
+ * Note, there is no synchronization between this and a user
+ * setting the tracing_on file. But we currently don't care
+ * about that.
+ */
+ if (!old_count)
+ return;
- if (*count != -1)
- (*count)--;
+ /* Make sure we see count before checking tracing state */
+ smp_rmb();
- return 1;
+ if (on == !!tracing_is_on())
+ return;
+
+ if (on)
+ tracing_on();
+ else
+ tracing_off();
+
+ /* unlimited? */
+ if (old_count == -1)
+ return;
+
+ /* Make sure tracing state is visible before updating count */
+ smp_wmb();
+
+ *count = old_count - 1;
}
static void
ftrace_traceon_count(unsigned long ip, unsigned long parent_ip, void **data)
{
- if (tracing_is_on())
- return;
-
- if (update_count(data))
- tracing_on();
+ update_traceon_count(data, 1);
}
static void
ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip, void **data)
{
- if (!tracing_is_on())
- return;
-
- if (update_count(data))
- tracing_off();
+ update_traceon_count(data, 0);
}
static void
static void
ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data)
{
- if (!tracing_is_on())
- return;
+ long *count = (long *)data;
+ long old_count;
+ long new_count;
- if (update_count(data))
- trace_dump_stack(STACK_SKIP);
+ /*
+ * Stack traces should only execute the number of times the
+ * user specified in the counter.
+ */
+ do {
+
+ if (!tracing_is_on())
+ return;
+
+ old_count = *count;
+
+ if (!old_count)
+ return;
+
+ /* unlimited? */
+ if (old_count == -1) {
+ trace_dump_stack(STACK_SKIP);
+ return;
+ }
+
+ new_count = old_count - 1;
+ new_count = cmpxchg(count, old_count, new_count);
+ if (new_count == old_count)
+ trace_dump_stack(STACK_SKIP);
+
+ } while (new_count != old_count);
+}
+
+static int update_count(void **data)
+{
+ unsigned long *count = (long *)data;
+
+ if (!*count)
+ return 0;
+
+ if (*count != -1)
+ (*count)--;
+
+ return 1;
}
static void
seq_printf(m, "%ps:%s", (void *)ip, name);
if (count == -1)
- seq_printf(m, ":unlimited\n");
+ seq_puts(m, ":unlimited\n");
else
seq_printf(m, ":count=%ld\n", count);
projects / firefly-linux-kernel-4.4.55.git / blobdiff