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tracing: Postpone tracer start-up tests till the system is more robust

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As tracing can now be enabled very early in boot up, even before some
critical system services (like scheduling), do not run the tracer selftests
until after early_initcall() is performed. If a tracer is registered before
such time, it is saved off in a list and the test is run when the system is
able to handle more diverse functions.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2017-03-24 17:59:10 -04:00
parent f631718de3
commit 9afecfbb95
1 changed files with 71 additions and 0 deletions
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71
kernel/trace/trace.c
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@ -1424,6 +1424,28 @@ static int wait_on_pipe(struct trace_iterator *iter, bool full)
}
#ifdef CONFIG_FTRACE_STARTUP_TEST
static bool selftests_can_run;
struct trace_selftests {
struct list_head list;
struct tracer *type;
};
static LIST_HEAD(postponed_selftests);
static int save_selftest(struct tracer *type)
{
struct trace_selftests *selftest;
selftest = kmalloc(sizeof(*selftest), GFP_KERNEL);
if (!selftest)
return -ENOMEM;
selftest->type = type;
list_add(&selftest->list, &postponed_selftests);
return 0;
}
static int run_tracer_selftest(struct tracer *type)
{
struct trace_array *tr = &global_trace;
@ -1433,6 +1455,14 @@ static int run_tracer_selftest(struct tracer *type)
if (!type->selftest || tracing_selftest_disabled)
return 0;
/*
* If a tracer registers early in boot up (before scheduling is
* initialized and such), then do not run its selftests yet.
* Instead, run it a little later in the boot process.
*/
if (!selftests_can_run)
return save_selftest(type);
/*
* Run a selftest on this tracer.
* Here we reset the trace buffer, and set the current
@ -1482,6 +1512,47 @@ static int run_tracer_selftest(struct tracer *type)
printk(KERN_CONT "PASSED\n");
return 0;
}
static __init int init_trace_selftests(void)
{
struct trace_selftests *p, *n;
struct tracer *t, **last;
int ret;
selftests_can_run = true;
mutex_lock(&trace_types_lock);
if (list_empty(&postponed_selftests))
goto out;
pr_info("Running postponed tracer tests:\n");
list_for_each_entry_safe(p, n, &postponed_selftests, list) {
ret = run_tracer_selftest(p->type);
/* If the test fails, then warn and remove from available_tracers */
if (ret < 0) {
WARN(1, "tracer: %s failed selftest, disabling\n",
p->type->name);
last = &trace_types;
for (t = trace_types; t; t = t->next) {
if (t == p->type) {
*last = t->next;
break;
}
last = &t->next;
}
}
list_del(&p->list);
kfree(p);
}
out:
mutex_unlock(&trace_types_lock);
return 0;
}
early_initcall(init_trace_selftests);
#else
static inline int run_tracer_selftest(struct tracer *type)
{