[PATCH 2/2] tracing: Use proper do_arch_spin_lock() API

[Waiman Long]

It was found that some tracing functions acquire a arch_spinlock_t with
preemption and irqs enabled.  That can be problematic in case preemption
happens after acquiring the lock. Use the proper do_arch_spin_lock()
API with preemption disabled to make sure that this won't happen unless
it is obvious that either preemption or irqs has been disabled .

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
 kernel/trace/trace.c | 52 ++++++++++++++++++++------------------------
 1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d3005279165d..cbb8520842ad 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1193,12 +1193,12 @@ void *tracing_cond_snapshot_data(struct trace_array *tr)
 {
 	void *cond_data = NULL;
 
-	arch_spin_lock(&tr->max_lock);
+	do_arch_spin_lock(&tr->max_lock);
 
 	if (tr->cond_snapshot)
 		cond_data = tr->cond_snapshot->cond_data;
 
-	arch_spin_unlock(&tr->max_lock);
+	do_arch_spin_unlock(&tr->max_lock);
 
 	return cond_data;
 }
@@ -1334,9 +1334,9 @@ int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data,
 		goto fail_unlock;
 	}
 
-	arch_spin_lock(&tr->max_lock);
+	do_arch_spin_lock(&tr->max_lock);
 	tr->cond_snapshot = cond_snapshot;
-	arch_spin_unlock(&tr->max_lock);
+	do_arch_spin_unlock(&tr->max_lock);
 
 	mutex_unlock(&trace_types_lock);
 
@@ -1363,7 +1363,7 @@ int tracing_snapshot_cond_disable(struct trace_array *tr)
 {
 	int ret = 0;
 
-	arch_spin_lock(&tr->max_lock);
+	do_arch_spin_lock(&tr->max_lock);
 
 	if (!tr->cond_snapshot)
 		ret = -EINVAL;
@@ -1372,7 +1372,7 @@ int tracing_snapshot_cond_disable(struct trace_array *tr)
 		tr->cond_snapshot = NULL;
 	}
 
-	arch_spin_unlock(&tr->max_lock);
+	do_arch_spin_unlock(&tr->max_lock);
 
 	return ret;
 }
@@ -1819,7 +1819,7 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
 		return;
 	}
 
-	arch_spin_lock(&tr->max_lock);
+	do_arch_spin_lock(&tr->max_lock);
 
 	/* Inherit the recordable setting from array_buffer */
 	if (ring_buffer_record_is_set_on(tr->array_buffer.buffer))
@@ -1836,7 +1836,7 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
 	__update_max_tr(tr, tsk, cpu);
 
  out_unlock:
-	arch_spin_unlock(&tr->max_lock);
+	do_arch_spin_unlock(&tr->max_lock);
 }
 
 /**
@@ -1862,7 +1862,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 		return;
 	}
 
-	arch_spin_lock(&tr->max_lock);
+	do_arch_spin_lock(&tr->max_lock);
 
 	ret = ring_buffer_swap_cpu(tr->max_buffer.buffer, tr->array_buffer.buffer, cpu);
 
@@ -1880,7 +1880,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 	WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY);
 
 	__update_max_tr(tr, tsk, cpu);
-	arch_spin_unlock(&tr->max_lock);
+	do_arch_spin_unlock(&tr->max_lock);
 }
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
@@ -2413,7 +2413,7 @@ static int trace_save_cmdline(struct task_struct *tsk)
 	 * nor do we want to disable interrupts,
 	 * so if we miss here, then better luck next time.
 	 */
-	if (!arch_spin_trylock(&trace_cmdline_lock))
+	if (!do_arch_spin_trylock(&trace_cmdline_lock))
 		return 0;
 
 	idx = savedcmd->map_pid_to_cmdline[tpid];
@@ -2427,7 +2427,7 @@ static int trace_save_cmdline(struct task_struct *tsk)
 	savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
 	set_cmdline(idx, tsk->comm);
 
-	arch_spin_unlock(&trace_cmdline_lock);
+	do_arch_spin_unlock(&trace_cmdline_lock);
 
 	return 1;
 }
@@ -2461,13 +2461,11 @@ static void __trace_find_cmdline(int pid, char comm[])
 
 void trace_find_cmdline(int pid, char comm[])
 {
-	preempt_disable();
-	arch_spin_lock(&trace_cmdline_lock);
+	do_arch_spin_lock(&trace_cmdline_lock);
 
 	__trace_find_cmdline(pid, comm);
 
-	arch_spin_unlock(&trace_cmdline_lock);
-	preempt_enable();
+	do_arch_spin_unlock(&trace_cmdline_lock);
 }
 
 static int *trace_find_tgid_ptr(int pid)
@@ -5829,8 +5827,7 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
 	void *v;
 	loff_t l = 0;
 
-	preempt_disable();
-	arch_spin_lock(&trace_cmdline_lock);
+	do_arch_spin_lock(&trace_cmdline_lock);
 
 	v = &savedcmd->map_cmdline_to_pid[0];
 	while (l <= *pos) {
@@ -5844,8 +5841,7 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
 
 static void saved_cmdlines_stop(struct seq_file *m, void *v)
 {
-	arch_spin_unlock(&trace_cmdline_lock);
-	preempt_enable();
+	do_arch_spin_unlock(&trace_cmdline_lock);
 }
 
 static int saved_cmdlines_show(struct seq_file *m, void *v)
@@ -5890,9 +5886,9 @@ tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
 	char buf[64];
 	int r;
 
-	arch_spin_lock(&trace_cmdline_lock);
+	do_arch_spin_lock(&trace_cmdline_lock);
 	r = scnprintf(buf, sizeof(buf), "%u\n", savedcmd->cmdline_num);
-	arch_spin_unlock(&trace_cmdline_lock);
+	do_arch_spin_unlock(&trace_cmdline_lock);
 
 	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 }
@@ -5917,10 +5913,10 @@ static int tracing_resize_saved_cmdlines(unsigned int val)
 		return -ENOMEM;
 	}
 
-	arch_spin_lock(&trace_cmdline_lock);
+	do_arch_spin_lock(&trace_cmdline_lock);
 	savedcmd_temp = savedcmd;
 	savedcmd = s;
-	arch_spin_unlock(&trace_cmdline_lock);
+	do_arch_spin_unlock(&trace_cmdline_lock);
 	free_saved_cmdlines_buffer(savedcmd_temp);
 
 	return 0;
@@ -6373,10 +6369,10 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
 
 #ifdef CONFIG_TRACER_SNAPSHOT
 	if (t->use_max_tr) {
-		arch_spin_lock(&tr->max_lock);
+		do_arch_spin_lock(&tr->max_lock);
 		if (tr->cond_snapshot)
 			ret = -EBUSY;
-		arch_spin_unlock(&tr->max_lock);
+		do_arch_spin_unlock(&tr->max_lock);
 		if (ret)
 			goto out;
 	}
@@ -7436,10 +7432,10 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
 		goto out;
 	}
 
-	arch_spin_lock(&tr->max_lock);
+	do_arch_spin_lock(&tr->max_lock);
 	if (tr->cond_snapshot)
 		ret = -EBUSY;
-	arch_spin_unlock(&tr->max_lock);
+	do_arch_spin_unlock(&tr->max_lock);
 	if (ret)
 		goto out;
 
-- 
2.31.1