1 files changed, 73 insertions, 5 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d3005279165d..47a44b055a1d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1193,12 +1193,14 @@ void *tracing_cond_snapshot_data(struct trace_array *tr)
 {
 	void *cond_data = NULL;
 
+	local_irq_disable();
 	arch_spin_lock(&tr->max_lock);
 
 	if (tr->cond_snapshot)
 		cond_data = tr->cond_snapshot->cond_data;
 
 	arch_spin_unlock(&tr->max_lock);
+	local_irq_enable();
 
 	return cond_data;
 }
@@ -1334,9 +1336,11 @@ int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data,
 		goto fail_unlock;
 	}
 
+	local_irq_disable();
 	arch_spin_lock(&tr->max_lock);
 	tr->cond_snapshot = cond_snapshot;
 	arch_spin_unlock(&tr->max_lock);
+	local_irq_enable();
 
 	mutex_unlock(&trace_types_lock);
 
@@ -1363,6 +1367,7 @@ int tracing_snapshot_cond_disable(struct trace_array *tr)
 {
 	int ret = 0;
 
+	local_irq_disable();
 	arch_spin_lock(&tr->max_lock);
 
 	if (!tr->cond_snapshot)
@@ -1373,6 +1378,7 @@ int tracing_snapshot_cond_disable(struct trace_array *tr)
 	}
 
 	arch_spin_unlock(&tr->max_lock);
+	local_irq_enable();
 
 	return ret;
 }
@@ -2200,6 +2206,11 @@ static size_t tgid_map_max;
 
 #define SAVED_CMDLINES_DEFAULT 128
 #define NO_CMDLINE_MAP UINT_MAX
+/*
+ * Preemption must be disabled before acquiring trace_cmdline_lock.
+ * The various trace_arrays' max_lock must be acquired in a context
+ * where interrupt is disabled.
+ */
 static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
 struct saved_cmdlines_buffer {
 	unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
@@ -2412,7 +2423,11 @@ static int trace_save_cmdline(struct task_struct *tsk)
 	 * the lock, but we also don't want to spin
 	 * nor do we want to disable interrupts,
 	 * so if we miss here, then better luck next time.
+	 *
+	 * This is called within the scheduler and wake up, so interrupts
+	 * had better been disabled and run queue lock been held.
 	 */
+	lockdep_assert_preemption_disabled();
 	if (!arch_spin_trylock(&trace_cmdline_lock))
 		return 0;
 
@@ -5890,9 +5905,11 @@ tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
 	char buf[64];
 	int r;
 
+	preempt_disable();
 	arch_spin_lock(&trace_cmdline_lock);
 	r = scnprintf(buf, sizeof(buf), "%u\n", savedcmd->cmdline_num);
 	arch_spin_unlock(&trace_cmdline_lock);
+	preempt_enable();
 
 	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 }
@@ -5917,10 +5934,12 @@ static int tracing_resize_saved_cmdlines(unsigned int val)
 		return -ENOMEM;
 	}
 
+	preempt_disable();
 	arch_spin_lock(&trace_cmdline_lock);
 	savedcmd_temp = savedcmd;
 	savedcmd = s;
 	arch_spin_unlock(&trace_cmdline_lock);
+	preempt_enable();
 	free_saved_cmdlines_buffer(savedcmd_temp);
 
 	return 0;
@@ -6373,10 +6392,12 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
 
 #ifdef CONFIG_TRACER_SNAPSHOT
 	if (t->use_max_tr) {
+		local_irq_disable();
 		arch_spin_lock(&tr->max_lock);
 		if (tr->cond_snapshot)
 			ret = -EBUSY;
 		arch_spin_unlock(&tr->max_lock);
+		local_irq_enable();
 		if (ret)
 			goto out;
 	}
@@ -6407,12 +6428,12 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
 	if (tr->current_trace->reset)
 		tr->current_trace->reset(tr);
 
+#ifdef CONFIG_TRACER_MAX_TRACE
+	had_max_tr = tr->current_trace->use_max_tr;
+
 	/* Current trace needs to be nop_trace before synchronize_rcu */
 	tr->current_trace = &nop_trace;
 
-#ifdef CONFIG_TRACER_MAX_TRACE
-	had_max_tr = tr->allocated_snapshot;
-
 	if (had_max_tr && !t->use_max_tr) {
 		/*
 		 * We need to make sure that the update_max_tr sees that
@@ -6425,11 +6446,13 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
 		free_snapshot(tr);
 	}
 
-	if (t->use_max_tr && !had_max_tr) {
+	if (t->use_max_tr && !tr->allocated_snapshot) {
 		ret = tracing_alloc_snapshot_instance(tr);
 		if (ret < 0)
 			goto out;
 	}
+#else
+	tr->current_trace = &nop_trace;
 #endif
 
 	if (t->init) {
@@ -7436,10 +7459,12 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
 		goto out;
 	}
 
+	local_irq_disable();
 	arch_spin_lock(&tr->max_lock);
 	if (tr->cond_snapshot)
 		ret = -EBUSY;
 	arch_spin_unlock(&tr->max_lock);
+	local_irq_enable();
 	if (ret)
 		goto out;
 
@@ -8137,6 +8162,12 @@ static int tracing_buffers_release(struct inode *inode, struct file *file)
 
 	__trace_array_put(iter->tr);
 
+	iter->wait_index++;
+	/* Make sure the waiters see the new wait_index */
+	smp_wmb();
+
+	ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file);
+
 	if (info->spare)
 		ring_buffer_free_read_page(iter->array_buffer->buffer,
 					   info->spare_cpu, info->spare);
@@ -8290,6 +8321,8 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 
 	/* did we read anything? */
 	if (!spd.nr_pages) {
+		long wait_index;
+
 		if (ret)
 			goto out;
 
@@ -8297,10 +8330,21 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 		if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK))
 			goto out;
 
+		wait_index = READ_ONCE(iter->wait_index);
+
 		ret = wait_on_pipe(iter, iter->tr->buffer_percent);
 		if (ret)
 			goto out;
 
+		/* No need to wait after waking up when tracing is off */
+		if (!tracer_tracing_is_on(iter->tr))
+			goto out;
+
+		/* Make sure we see the new wait_index */
+		smp_rmb();
+		if (wait_index != iter->wait_index)
+			goto out;
+
 		goto again;
 	}
 
@@ -8311,12 +8355,34 @@ out:
 	return ret;
 }
 
+/* An ioctl call with cmd 0 to the ring buffer file will wake up all waiters */
+static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct ftrace_buffer_info *info = file->private_data;
+	struct trace_iterator *iter = &info->iter;
+
+	if (cmd)
+		return -ENOIOCTLCMD;
+
+	mutex_lock(&trace_types_lock);
+
+	iter->wait_index++;
+	/* Make sure the waiters see the new wait_index */
+	smp_wmb();
+
+	ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file);
+
+	mutex_unlock(&trace_types_lock);
+	return 0;
+}
+
 static const struct file_operations tracing_buffers_fops = {
 	.open		= tracing_buffers_open,
 	.read		= tracing_buffers_read,
 	.poll		= tracing_buffers_poll,
 	.release	= tracing_buffers_release,
 	.splice_read	= tracing_buffers_splice_read,
+	.unlocked_ioctl = tracing_buffers_ioctl,
 	.llseek		= no_llseek,
 };
 
@@ -9005,6 +9071,8 @@ rb_simple_write(struct file *filp, const char __user *ubuf,
 			tracer_tracing_off(tr);
 			if (tr->current_trace->stop)
 				tr->current_trace->stop(tr);
+			/* Wake up any waiters */
+			ring_buffer_wake_waiters(buffer, RING_BUFFER_ALL_CPUS);
 		}
 		mutex_unlock(&trace_types_lock);
 	}
@@ -10091,7 +10159,7 @@ __init static int tracer_alloc_buffers(void)
 	 * buffer. The memory will be removed once the "instance" is removed.
 	 */
 	ret = cpuhp_setup_state_multi(CPUHP_TRACE_RB_PREPARE,
-				      "trace/RB:preapre", trace_rb_cpu_prepare,
+				      "trace/RB:prepare", trace_rb_cpu_prepare,
 				      NULL);
 	if (ret < 0)
 		goto out_free_cpumask;