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tracing: Do not start benchmark on boot up 

Trace events are enabled very early on boot up via the boot command line
parameter. The benchmark tool creates a new thread to perform the trace
event benchmarking. But at start up, it is called before scheduling is set
up and because it creates a new thread before the init thread is created,
this crashes the kernel.

Have the benchmark fail to register when started via the kernel command
line.

Also, since the registering of a tracepoint now can handle failure cases,
return -ENOMEM instead of warning if the thread cannot be created.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2016-11-28 13:17:25 -05:00 committed by Steven Rostedt
parent 8cf868affd
commit 1dd349ab74
1 changed files with 11 additions and 1 deletions
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12
kernel/trace/trace_benchmark.c
View File

@ -166,9 +166,18 @@ static int benchmark_event_kthread(void *arg)
*/ */
int trace_benchmark_reg(void) int trace_benchmark_reg(void)
{ {
if (system_state != SYSTEM_RUNNING) {
pr_warning("trace benchmark cannot be started via kernel command line\n");
return -EBUSY;
}
bm_event_thread = kthread_run(benchmark_event_kthread, bm_event_thread = kthread_run(benchmark_event_kthread,
NULL, "event_benchmark"); NULL, "event_benchmark");
WARN_ON(!bm_event_thread); if (!bm_event_thread) {
pr_warning("trace benchmark failed to create kernel thread\n");
return -ENOMEM;
}
return 0; return 0;
} }
@ -183,6 +192,7 @@ void trace_benchmark_unreg(void)
return; return;
kthread_stop(bm_event_thread); kthread_stop(bm_event_thread);
bm_event_thread = NULL;
strcpy(bm_str, "START"); strcpy(bm_str, "START");
bm_total = 0; bm_total = 0;