2 files changed, 342 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index f78eab251897..0b5ecf5517fa 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -565,6 +565,29 @@ config RING_BUFFER_BENCHMARK
 
           If unsure, say N.
 
+config RING_BUFFER_STARTUP_TEST
+       bool "Ring buffer startup self test"
+       depends on RING_BUFFER
+       help
+         Run a simple self test on the ring buffer on boot up. Late in the
+         kernel boot sequence, the test will start that kicks off
+         a thread per cpu. Each thread will write various size events
+         into the ring buffer. Another thread is created to send IPIs
+         to each of the threads, where the IPI handler will also write
+         to the ring buffer, to test/stress the nesting ability.
+         If any anomalies are discovered, a warning will be displayed
+         and all ring buffers will be disabled.
+
+         The test runs for 10 seconds. This will slow your boot time
+         by at least 10 more seconds.
+
+         At the end of the test, statics and more checks are done.
+         It will output the stats of each per cpu buffer. What
+         was written, the sizes, what was read, what was lost, and
+         other similar details.
+
+         If unsure, say N
+
 endif # FTRACE
 
 endif # TRACING_SUPPORT
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index d1c85c5f5f51..e5472f7bc347 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -12,10 +12,12 @@
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/hardirq.h>
+#include <linux/kthread.h>      /* for self test */
 #include <linux/kmemcheck.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/mutex.h>
+#include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/hash.h>
@@ -4634,3 +4636,320 @@ static int rb_cpu_notify(struct notifier_block *self,
         return NOTIFY_OK;
 }
 #endif
+
+#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
+/*
+ * This is a basic integrity check of the ring buffer.
+ * Late in the boot cycle this test will run when configured in.
+ * It will kick off a thread per CPU that will go into a loop
+ * writing to the per cpu ring buffer various sizes of data.
+ * Some of the data will be large items, some small.
+ *
+ * Another thread is created that goes into a spin, sending out
+ * IPIs to the other CPUs to also write into the ring buffer.
+ * this is to test the nesting ability of the buffer.
+ *
+ * Basic stats are recorded and reported. If something in the
+ * ring buffer should happen that's not expected, a big warning
+ * is displayed and all ring buffers are disabled.
+ */
+static struct task_struct *rb_threads[NR_CPUS] __initdata;
+
+struct rb_test_data {
+        struct ring_buffer      *buffer;
+        unsigned long           events;
+        unsigned long           bytes_written;
+        unsigned long           bytes_alloc;
+        unsigned long           bytes_dropped;
+        unsigned long           events_nested;
+        unsigned long           bytes_written_nested;
+        unsigned long           bytes_alloc_nested;
+        unsigned long           bytes_dropped_nested;
+        int                     min_size_nested;
+        int                     max_size_nested;
+        int                     max_size;
+        int                     min_size;
+        int                     cpu;
+        int                     cnt;
+};
+
+static struct rb_test_data rb_data[NR_CPUS] __initdata;
+
+/* 1 meg per cpu */
+#define RB_TEST_BUFFER_SIZE     1048576
+
+static char rb_string[] __initdata =
+        "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
+        "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
+        "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
+
+static bool rb_test_started __initdata;
+
+struct rb_item {
+        int size;
+        char str[];
+};
+
+static __init int rb_write_something(struct rb_test_data *data, bool nested)
+{
+        struct ring_buffer_event *event;
+        struct rb_item *item;
+        bool started;
+        int event_len;
+        int size;
+        int len;
+        int cnt;
+
+        /* Have nested writes different that what is written */
+        cnt = data->cnt + (nested ? 27 : 0);
+
+        /* Multiply cnt by ~e, to make some unique increment */
+        size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
+
+        len = size + sizeof(struct rb_item);
+
+        started = rb_test_started;
+        /* read rb_test_started before checking buffer enabled */
+        smp_rmb();
+
+        event = ring_buffer_lock_reserve(data->buffer, len);
+        if (!event) {
+                /* Ignore dropped events before test starts. */
+                if (started) {
+                        if (nested)
+                                data->bytes_dropped += len;
+                        else
+                                data->bytes_dropped_nested += len;
+                }
+                return len;
+        }
+
+        event_len = ring_buffer_event_length(event);
+
+        if (RB_WARN_ON(data->buffer, event_len < len))
+                goto out;
+
+        item = ring_buffer_event_data(event);
+        item->size = size;
+        memcpy(item->str, rb_string, size);
+
+        if (nested) {
+                data->bytes_alloc_nested += event_len;
+                data->bytes_written_nested += len;
+                data->events_nested++;
+                if (!data->min_size_nested || len < data->min_size_nested)
+                        data->min_size_nested = len;
+                if (len > data->max_size_nested)
+                        data->max_size_nested = len;
+        } else {
+                data->bytes_alloc += event_len;
+                data->bytes_written += len;
+                data->events++;
+                if (!data->min_size || len < data->min_size)
+                        data->max_size = len;
+                if (len > data->max_size)
+                        data->max_size = len;
+        }
+
+ out:
+        ring_buffer_unlock_commit(data->buffer, event);
+
+        return 0;
+}
+
+static __init int rb_test(void *arg)
+{
+        struct rb_test_data *data = arg;
+
+        while (!kthread_should_stop()) {
+                rb_write_something(data, false);
+                data->cnt++;
+
+                set_current_state(TASK_INTERRUPTIBLE);
+                /* Now sleep between a min of 100-300us and a max of 1ms */
+                usleep_range(((data->cnt % 3) + 1) * 100, 1000);
+        }
+
+        return 0;
+}
+
+static __init void rb_ipi(void *ignore)
+{
+        struct rb_test_data *data;
+        int cpu = smp_processor_id();
+
+        data = &rb_data[cpu];
+        rb_write_something(data, true);
+}
+
+static __init int rb_hammer_test(void *arg)
+{
+        while (!kthread_should_stop()) {
+
+                /* Send an IPI to all cpus to write data! */
+                smp_call_function(rb_ipi, NULL, 1);
+                /* No sleep, but for non preempt, let others run */
+                schedule();
+        }
+
+        return 0;
+}
+
+static __init int test_ringbuffer(void)
+{
+        struct task_struct *rb_hammer;
+        struct ring_buffer *buffer;
+        int cpu;
+        int ret = 0;
+
+        pr_info("Running ring buffer tests...\n");
+
+        buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
+        if (WARN_ON(!buffer))
+                return 0;
+
+        /* Disable buffer so that threads can't write to it yet */
+        ring_buffer_record_off(buffer);
+
+        for_each_online_cpu(cpu) {
+                rb_data[cpu].buffer = buffer;
+                rb_data[cpu].cpu = cpu;
+                rb_data[cpu].cnt = cpu;
+                rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
+                                                 "rbtester/%d", cpu);
+                if (WARN_ON(!rb_threads[cpu])) {
+                        pr_cont("FAILED\n");
+                        ret = -1;
+                        goto out_free;
+                }
+
+                kthread_bind(rb_threads[cpu], cpu);
+                wake_up_process(rb_threads[cpu]);
+        }
+
+        /* Now create the rb hammer! */
+        rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
+        if (WARN_ON(!rb_hammer)) {
+                pr_cont("FAILED\n");
+                ret = -1;
+                goto out_free;
+        }
+
+        ring_buffer_record_on(buffer);
+        /*
+         * Show buffer is enabled before setting rb_test_started.
+         * Yes there's a small race window where events could be
+         * dropped and the thread wont catch it. But when a ring
+         * buffer gets enabled, there will always be some kind of
+         * delay before other CPUs see it. Thus, we don't care about
+         * those dropped events. We care about events dropped after
+         * the threads see that the buffer is active.
+         */
+        smp_wmb();
+        rb_test_started = true;
+
+        set_current_state(TASK_INTERRUPTIBLE);
+        /* Just run for 10 seconds */;
+        schedule_timeout(10 * HZ);
+
+        kthread_stop(rb_hammer);
+
+ out_free:
+        for_each_online_cpu(cpu) {
+                if (!rb_threads[cpu])
+                        break;
+                kthread_stop(rb_threads[cpu]);
+        }
+        if (ret) {
+                ring_buffer_free(buffer);
+                return ret;
+        }
+
+        /* Report! */
+        pr_info("finished\n");
+        for_each_online_cpu(cpu) {
+                struct ring_buffer_event *event;
+                struct rb_test_data *data = &rb_data[cpu];
+                struct rb_item *item;
+                unsigned long total_events;
+                unsigned long total_dropped;
+                unsigned long total_written;
+                unsigned long total_alloc;
+                unsigned long total_read = 0;
+                unsigned long total_size = 0;
+                unsigned long total_len = 0;
+                unsigned long total_lost = 0;
+                unsigned long lost;
+                int big_event_size;
+                int small_event_size;
+
+                ret = -1;
+
+                total_events = data->events + data->events_nested;
+                total_written = data->bytes_written + data->bytes_written_nested;
+                total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
+                total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
+
+                big_event_size = data->max_size + data->max_size_nested;
+                small_event_size = data->min_size + data->min_size_nested;
+
+                pr_info("CPU %d:\n", cpu);
+                pr_info("              events:    %ld\n", total_events);
+                pr_info("       dropped bytes:    %ld\n", total_dropped);
+                pr_info("       alloced bytes:    %ld\n", total_alloc);
+                pr_info("       written bytes:    %ld\n", total_written);
+                pr_info("       biggest event:    %d\n", big_event_size);
+                pr_info("      smallest event:    %d\n", small_event_size);
+
+                if (RB_WARN_ON(buffer, total_dropped))
+                        break;
+
+                ret = 0;
+
+                while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
+                        total_lost += lost;
+                        item = ring_buffer_event_data(event);
+                        total_len += ring_buffer_event_length(event);
+                        total_size += item->size + sizeof(struct rb_item);
+                        if (memcmp(&item->str[0], rb_string, item->size) != 0) {
+                                pr_info("FAILED!\n");
+                                pr_info("buffer had: %.*s\n", item->size, item->str);
+                                pr_info("expected:   %.*s\n", item->size, rb_string);
+                                RB_WARN_ON(buffer, 1);
+                                ret = -1;
+                                break;
+                        }
+                        total_read++;
+                }
+                if (ret)
+                        break;
+
+                ret = -1;
+
+                pr_info("         read events:   %ld\n", total_read);
+                pr_info("         lost events:   %ld\n", total_lost);
+                pr_info("        total events:   %ld\n", total_lost + total_read);
+                pr_info("  recorded len bytes:   %ld\n", total_len);
+                pr_info(" recorded size bytes:   %ld\n", total_size);
+                if (total_lost)
+                        pr_info(" With dropped events, record len and size may not match\n"
+                                " alloced and written from above\n");
+                if (!total_lost) {
+                        if (RB_WARN_ON(buffer, total_len != total_alloc ||
+                                       total_size != total_written))
+                                break;
+                }
+                if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
+                        break;
+
+                ret = 0;
+        }
+        if (!ret)
+                pr_info("Ring buffer PASSED!\n");
+
+        ring_buffer_free(buffer);
+        return 0;
+}
+
+late_initcall(test_ringbuffer);
+#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */