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ring_buffer: Fix more races when terminating the producer in the benchmark

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The commit b44754d826 ("ring_buffer: Allow to exit the ring
buffer benchmark immediately") added a hack into ring_buffer_producer()
that set @kill_test when kthread_should_stop() returned true. It improved
the situation a lot. It stopped the kthread in most cases because
the producer spent most of the time in the patched while cycle.

But there are still few possible races when kthread_should_stop()
is set outside of the cycle. Then we do not set @kill_test and
some other checks pass.

This patch adds a better fix. It renames @test_kill/TEST_KILL() into
a better descriptive @test_error/TEST_ERROR(). Also it introduces
break_test() function that checks for both @test_error and
kthread_should_stop().

The new function is used in the producer when the check for @test_error
is not enough. It is not used in the consumer because its state
is manipulated by the producer via the "reader_finish" variable.

Also we add a missing check into ring_buffer_producer_thread()
between setting TASK_INTERRUPTIBLE and calling schedule_timeout().
Otherwise, we might miss a wakeup from kthread_stop().

Link: http://lkml.kernel.org/r/1441629518-32712-3-git-send-email-pmladek@suse.com

Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Petr Mladek 2015-09-07 14:38:38 +02:00 committed by Steven Rostedt
parent 8b46ff6938
commit f47cb66df2
1 changed files with 29 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
kernel/trace/ring_buffer_benchmark.c
View File

@ -60,12 +60,12 @@ MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");
static int read_events;
static int kill_test;
static int test_error;
#define KILL_TEST() \
#define TEST_ERROR() \
do { \
if (!kill_test) { \
kill_test = 1; \
if (!test_error) { \
test_error = 1; \
WARN_ON(1); \
} \
} while (0)
@ -75,6 +75,11 @@ enum event_status {
EVENT_DROPPED,
};
static bool break_test(void)
{
return test_error || kthread_should_stop();
}
static enum event_status read_event(int cpu)
{
struct ring_buffer_event *event;
@ -87,7 +92,7 @@ static enum event_status read_event(int cpu)
entry = ring_buffer_event_data(event);
if (*entry != cpu) {
KILL_TEST();
TEST_ERROR();
return EVENT_DROPPED;
}
@ -115,10 +120,10 @@ static enum event_status read_page(int cpu)
rpage = bpage;
/* The commit may have missed event flags set, clear them */
commit = local_read(&rpage->commit) & 0xfffff;
for (i = 0; i < commit && !kill_test; i += inc) {
for (i = 0; i < commit && !test_error ; i += inc) {
if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {
KILL_TEST();
TEST_ERROR();
break;
}
@ -128,7 +133,7 @@ static enum event_status read_page(int cpu)
case RINGBUF_TYPE_PADDING:
/* failed writes may be discarded events */
if (!event->time_delta)
KILL_TEST();
TEST_ERROR();
inc = event->array[0] + 4;
break;
case RINGBUF_TYPE_TIME_EXTEND:
@ -137,12 +142,12 @@ static enum event_status read_page(int cpu)
case 0:
entry = ring_buffer_event_data(event);
if (*entry != cpu) {
KILL_TEST();
TEST_ERROR();
break;
}
read++;
if (!event->array[0]) {
KILL_TEST();
TEST_ERROR();
break;
}
inc = event->array[0] + 4;
@ -150,17 +155,17 @@ static enum event_status read_page(int cpu)
default:
entry = ring_buffer_event_data(event);
if (*entry != cpu) {
KILL_TEST();
TEST_ERROR();
break;
}
read++;
inc = ((event->type_len + 1) * 4);
}
if (kill_test)
if (test_error)
break;
if (inc <= 0) {
KILL_TEST();
TEST_ERROR();
break;
}
}
@ -185,7 +190,7 @@ static void ring_buffer_consumer(void)
while (!READ_ONCE(reader_finish)) {
int found = 1;
while (found && !kill_test) {
while (found && !test_error) {
int cpu;
found = 0;
@ -197,7 +202,7 @@ static void ring_buffer_consumer(void)
else
stat = read_page(cpu);
if (kill_test)
if (test_error)
break;
if (stat == EVENT_FOUND)
@ -273,10 +278,7 @@ static void ring_buffer_producer(void)
if (cnt % wakeup_interval)
cond_resched();
#endif
if (kthread_should_stop())
kill_test = 1;
} while (ktime_before(end_time, timeout) && !kill_test);
} while (ktime_before(end_time, timeout) && !break_test());
trace_printk("End ring buffer hammer\n");
if (consumer) {
@ -297,7 +299,7 @@ static void ring_buffer_producer(void)
entries = ring_buffer_entries(buffer);
overruns = ring_buffer_overruns(buffer);
if (kill_test && !kthread_should_stop())
if (test_error)
trace_printk("ERROR!\n");
if (!disable_reader) {
@ -378,15 +380,14 @@ static void wait_to_die(void)
static int ring_buffer_consumer_thread(void *arg)
{
while (!kthread_should_stop() && !kill_test) {
while (!break_test()) {
complete(&read_start);
ring_buffer_consumer();
set_current_state(TASK_INTERRUPTIBLE);
if (kthread_should_stop() || kill_test)
if (break_test())
break;
schedule();
}
__set_current_state(TASK_RUNNING);
@ -399,7 +400,7 @@ static int ring_buffer_consumer_thread(void *arg)
static int ring_buffer_producer_thread(void *arg)
{
while (!kthread_should_stop() && !kill_test) {
while (!break_test()) {
ring_buffer_reset(buffer);
if (consumer) {
@ -408,15 +409,18 @@ static int ring_buffer_producer_thread(void *arg)
}
ring_buffer_producer();
if (kill_test)
if (break_test())
goto out_kill;
trace_printk("Sleeping for 10 secs\n");
set_current_state(TASK_INTERRUPTIBLE);
if (break_test())
goto out_kill;
schedule_timeout(HZ * SLEEP_TIME);
}
out_kill:
__set_current_state(TASK_RUNNING);
if (!kthread_should_stop())
wait_to_die();