Merge branch 'tracing/syscalls' into tracing/core

kernel/trace/Kconfig

@@ -182,6 +182,7 @@ config FTRACE_SYSCALLS
 	bool "Trace syscalls"
 	depends on HAVE_FTRACE_SYSCALLS
 	select TRACING
+	select KALLSYMS
 	help
 	  Basic tracer to catch the syscall entry and exit events.
 

kernel/trace/trace.c

@@ -2494,7 +2494,7 @@ static int tracing_set_tracer(const char *buf)
 	if (!ring_buffer_expanded) {
 		ret = tracing_resize_ring_buffer(trace_buf_size);
 		if (ret < 0)
-			return ret;
+			goto out;
 		ret = 0;
 	}
 
@@ -4125,7 +4125,8 @@ __init static int tracer_alloc_buffers(void)
 				       &trace_panic_notifier);
 
 	register_die_notifier(&trace_die_notifier);
-	ret = 0;
+
+	return 0;
 
 out_free_cpumask:
 	free_cpumask_var(tracing_reader_cpumask);

kernel/trace/trace_selftest.c

@@ -414,7 +414,7 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
 	ret = tracer_init(trace, tr);
 	if (ret) {
 		warn_failed_init_tracer(trace, ret);
-		goto out;
+		goto out_no_start;
 	}
 
 	/* reset the max latency */
@@ -432,21 +432,16 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
 	tracing_stop();
 	/* check both trace buffers */
 	ret = trace_test_buffer(tr, NULL);
-	if (ret) {
-		tracing_start();
+	if (ret)
 		goto out;
-	}
 
 	ret = trace_test_buffer(&max_tr, &count);
-	if (ret) {
-		tracing_start();
+	if (ret)
 		goto out;
-	}
 
 	if (!ret && !count) {
 		printk(KERN_CONT ".. no entries found ..");
 		ret = -1;
-		tracing_start();
 		goto out;
 	}
 
@@ -475,9 +470,10 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
 		goto out;
 	}
 
- out:
-	trace->reset(tr);
+out:
 	tracing_start();
+out_no_start:
+	trace->reset(tr);
 	tracing_max_latency = save_max;
 
 	return ret;

kernel/trace/trace_syscalls.c

@@ -5,9 +5,13 @@
 #include "trace_output.h"
 #include "trace.h"
 
-static atomic_t refcount;
+/* Keep a counter of the syscall tracing users */
+static int refcount;
 
-/* Our two options */
+/* Prevent from races on thread flags toggling */
+static DEFINE_MUTEX(syscall_trace_lock);
+
+/* Option to display the parameters types */
 enum {
 	TRACE_SYSCALLS_OPT_TYPES = 0x1,
 };
@@ -18,7 +22,7 @@ static struct tracer_opt syscalls_opts[] = {
 };
 
 static struct tracer_flags syscalls_flags = {
-	.val = 0, /* By default: no args types */
+	.val = 0, /* By default: no parameters types */
 	.opts = syscalls_opts
 };
 
@@ -96,8 +100,11 @@ void start_ftrace_syscalls(void)
 	unsigned long flags;
 	struct task_struct *g, *t;
 
-	if (atomic_inc_return(&refcount) != 1)
-		goto out;
+	mutex_lock(&syscall_trace_lock);
+
+	/* Don't enable the flag on the tasks twice */
+	if (++refcount != 1)
+		goto unlock;
 
 	arch_init_ftrace_syscalls();
 	read_lock_irqsave(&tasklist_lock, flags);
@@ -107,8 +114,9 @@ void start_ftrace_syscalls(void)
 	} while_each_thread(g, t);
 
 	read_unlock_irqrestore(&tasklist_lock, flags);
-out:
-	atomic_dec(&refcount);
+
+unlock:
+	mutex_unlock(&syscall_trace_lock);
 }
 
 void stop_ftrace_syscalls(void)
@@ -116,8 +124,11 @@ void stop_ftrace_syscalls(void)
 	unsigned long flags;
 	struct task_struct *g, *t;
 
-	if (atomic_dec_return(&refcount))
-		goto out;
+	mutex_lock(&syscall_trace_lock);
+
+	/* There are perhaps still some users */
+	if (--refcount)
+		goto unlock;
 
 	read_lock_irqsave(&tasklist_lock, flags);
 
@@ -126,8 +137,9 @@ void stop_ftrace_syscalls(void)
 	} while_each_thread(g, t);
 
 	read_unlock_irqrestore(&tasklist_lock, flags);
-out:
-	atomic_inc(&refcount);
+
+unlock:
+	mutex_unlock(&syscall_trace_lock);
 }
 
 void ftrace_syscall_enter(struct pt_regs *regs)
@@ -137,12 +149,9 @@ void ftrace_syscall_enter(struct pt_regs *regs)
 	struct ring_buffer_event *event;
 	int size;
 	int syscall_nr;
-	int cpu;
 
 	syscall_nr = syscall_get_nr(current, regs);
 
-	cpu = raw_smp_processor_id();
-
 	sys_data = syscall_nr_to_meta(syscall_nr);
 	if (!sys_data)
 		return;
@@ -168,12 +177,9 @@ void ftrace_syscall_exit(struct pt_regs *regs)
 	struct syscall_metadata *sys_data;
 	struct ring_buffer_event *event;
 	int syscall_nr;
-	int cpu;
 
 	syscall_nr = syscall_get_nr(current, regs);
 
-	cpu = raw_smp_processor_id();
-
 	sys_data = syscall_nr_to_meta(syscall_nr);
 	if (!sys_data)
 		return;
@@ -201,6 +207,7 @@ static int init_syscall_tracer(struct trace_array *tr)
 static void reset_syscall_tracer(struct trace_array *tr)
 {
 	stop_ftrace_syscalls();
+	tracing_reset_online_cpus(tr);
 }
 
 static struct trace_event syscall_enter_event = {