4 files changed, 34 insertions, 29 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 95a0ad191f19..b0a46f889659 100644
--- a/kernel/trace/Kconfig
+++ b/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.
 
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index efe3202c0209..ae32d3b99b4b 100644
--- a/kernel/trace/trace.c
+++ b/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);
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index f907a2b29028..a2ca6f0fef9b 100644
--- a/kernel/trace/trace_selftest.c
+++ b/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;
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index c72e599230ff..a2a3af29c943 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/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 = {