3 files changed, 141 insertions, 49 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ed7b5d1e12f4..1ab8e35d069b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1498,25 +1498,119 @@ static void __trace_userstack(struct trace_array *tr, unsigned long flags)
 
 #endif /* CONFIG_STACKTRACE */
 
+/* created for use with alloc_percpu */
+struct trace_buffer_struct {
+        char buffer[TRACE_BUF_SIZE];
+};
+
+static struct trace_buffer_struct *trace_percpu_buffer;
+static struct trace_buffer_struct *trace_percpu_sirq_buffer;
+static struct trace_buffer_struct *trace_percpu_irq_buffer;
+static struct trace_buffer_struct *trace_percpu_nmi_buffer;
+
+/*
+ * The buffer used is dependent on the context. There is a per cpu
+ * buffer for normal context, softirq contex, hard irq context and
+ * for NMI context. Thise allows for lockless recording.
+ *
+ * Note, if the buffers failed to be allocated, then this returns NULL
+ */
+static char *get_trace_buf(void)
+{
+        struct trace_buffer_struct *percpu_buffer;
+        struct trace_buffer_struct *buffer;
+
+        /*
+         * If we have allocated per cpu buffers, then we do not
+         * need to do any locking.
+         */
+        if (in_nmi())
+                percpu_buffer = trace_percpu_nmi_buffer;
+        else if (in_irq())
+                percpu_buffer = trace_percpu_irq_buffer;
+        else if (in_softirq())
+                percpu_buffer = trace_percpu_sirq_buffer;
+        else
+                percpu_buffer = trace_percpu_buffer;
+
+        if (!percpu_buffer)
+                return NULL;
+
+        buffer = per_cpu_ptr(percpu_buffer, smp_processor_id());
+
+        return buffer->buffer;
+}
+
+static int alloc_percpu_trace_buffer(void)
+{
+        struct trace_buffer_struct *buffers;
+        struct trace_buffer_struct *sirq_buffers;
+        struct trace_buffer_struct *irq_buffers;
+        struct trace_buffer_struct *nmi_buffers;
+
+        buffers = alloc_percpu(struct trace_buffer_struct);
+        if (!buffers)
+                goto err_warn;
+
+        sirq_buffers = alloc_percpu(struct trace_buffer_struct);
+        if (!sirq_buffers)
+                goto err_sirq;
+
+        irq_buffers = alloc_percpu(struct trace_buffer_struct);
+        if (!irq_buffers)
+                goto err_irq;
+
+        nmi_buffers = alloc_percpu(struct trace_buffer_struct);
+        if (!nmi_buffers)
+                goto err_nmi;
+
+        trace_percpu_buffer = buffers;
+        trace_percpu_sirq_buffer = sirq_buffers;
+        trace_percpu_irq_buffer = irq_buffers;
+        trace_percpu_nmi_buffer = nmi_buffers;
+
+        return 0;
+
+ err_nmi:
+        free_percpu(irq_buffers);
+ err_irq:
+        free_percpu(sirq_buffers);
+ err_sirq:
+        free_percpu(buffers);
+ err_warn:
+        WARN(1, "Could not allocate percpu trace_printk buffer");
+        return -ENOMEM;
+}
+
+void trace_printk_init_buffers(void)
+{
+        static int buffers_allocated;
+
+        if (buffers_allocated)
+                return;
+
+        if (alloc_percpu_trace_buffer())
+                return;
+
+        pr_info("ftrace: Allocated trace_printk buffers\n");
+
+        buffers_allocated = 1;
+}
+
 /**
  * trace_vbprintk - write binary msg to tracing buffer
  *
  */
 int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
 {
-        static arch_spinlock_t trace_buf_lock =
-                (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
-        static u32 trace_buf[TRACE_BUF_SIZE];
-
         struct ftrace_event_call *call = &event_bprint;
         struct ring_buffer_event *event;
         struct ring_buffer *buffer;
         struct trace_array *tr = &global_trace;
-        struct trace_array_cpu *data;
         struct bprint_entry *entry;
         unsigned long flags;
-        int disable;
-        int cpu, len = 0, size, pc;
+        char *tbuffer;
+        int len = 0, size, pc;
 
         if (unlikely(tracing_selftest_running || tracing_disabled))
                 return 0;
@@ -1526,43 +1620,36 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
 
         pc = preempt_count();
         preempt_disable_notrace();
-        cpu = raw_smp_processor_id();
-        data = tr->data[cpu];
 
-        disable = atomic_inc_return(&data->disabled);
-        if (unlikely(disable != 1))
+        tbuffer = get_trace_buf();
+        if (!tbuffer) {
+                len = 0;
                 goto out;
+        }
 
-        /* Lockdep uses trace_printk for lock tracing */
-        local_irq_save(flags);
-        arch_spin_lock(&trace_buf_lock);
-        len = vbin_printf(trace_buf, TRACE_BUF_SIZE, fmt, args);
+        len = vbin_printf((u32 *)tbuffer, TRACE_BUF_SIZE/sizeof(int), fmt, args);
 
-        if (len > TRACE_BUF_SIZE || len < 0)
-                goto out_unlock;
+        if (len > TRACE_BUF_SIZE/sizeof(int) || len < 0)
+                goto out;
 
+        local_save_flags(flags);
         size = sizeof(*entry) + sizeof(u32) * len;
         buffer = tr->buffer;
         event = trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size,
                                           flags, pc);
         if (!event)
-                goto out_unlock;
+                goto out;
         entry = ring_buffer_event_data(event);
         entry->ip                       = ip;
         entry->fmt                      = fmt;
 
-        memcpy(entry->buf, trace_buf, sizeof(u32) * len);
+        memcpy(entry->buf, tbuffer, sizeof(u32) * len);
         if (!filter_check_discard(call, entry, buffer, event)) {
                 ring_buffer_unlock_commit(buffer, event);
                 ftrace_trace_stack(buffer, flags, 6, pc);
         }
 
-out_unlock:
-        arch_spin_unlock(&trace_buf_lock);
-        local_irq_restore(flags);
-
 out:
-        atomic_dec_return(&data->disabled);
         preempt_enable_notrace();
         unpause_graph_tracing();
 
@@ -1588,58 +1675,53 @@ int trace_array_printk(struct trace_array *tr,
 int trace_array_vprintk(struct trace_array *tr,
                         unsigned long ip, const char *fmt, va_list args)
 {
-        static arch_spinlock_t trace_buf_lock = __ARCH_SPIN_LOCK_UNLOCKED;
-        static char trace_buf[TRACE_BUF_SIZE];
-
         struct ftrace_event_call *call = &event_print;
         struct ring_buffer_event *event;
         struct ring_buffer *buffer;
-        struct trace_array_cpu *data;
-        int cpu, len = 0, size, pc;
+        int len = 0, size, pc;
         struct print_entry *entry;
-        unsigned long irq_flags;
-        int disable;
+        unsigned long flags;
+        char *tbuffer;
 
         if (tracing_disabled || tracing_selftest_running)
                 return 0;
 
+        /* Don't pollute graph traces with trace_vprintk internals */
+        pause_graph_tracing();
+
         pc = preempt_count();
         preempt_disable_notrace();
-        cpu = raw_smp_processor_id();
-        data = tr->data[cpu];
 
-        disable = atomic_inc_return(&data->disabled);
-        if (unlikely(disable != 1))
+
+        tbuffer = get_trace_buf();
+        if (!tbuffer) {
+                len = 0;
                 goto out;
+        }
 
-        pause_graph_tracing();
-        raw_local_irq_save(irq_flags);
-        arch_spin_lock(&trace_buf_lock);
-        len = vsnprintf(trace_buf, TRACE_BUF_SIZE, fmt, args);
+        len = vsnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args);
+        if (len > TRACE_BUF_SIZE)
+                goto out;
 
+        local_save_flags(flags);
         size = sizeof(*entry) + len + 1;
         buffer = tr->buffer;
         event = trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
-                                          irq_flags, pc);
+                                          flags, pc);
         if (!event)
-                goto out_unlock;
+                goto out;
         entry = ring_buffer_event_data(event);
         entry->ip = ip;
 
-        memcpy(&entry->buf, trace_buf, len);
+        memcpy(&entry->buf, tbuffer, len);
         entry->buf[len] = '\0';
         if (!filter_check_discard(call, entry, buffer, event)) {
                 ring_buffer_unlock_commit(buffer, event);
-                ftrace_trace_stack(buffer, irq_flags, 6, pc);
+                ftrace_trace_stack(buffer, flags, 6, pc);
         }
-
- out_unlock:
-        arch_spin_unlock(&trace_buf_lock);
-        raw_local_irq_restore(irq_flags);
-        unpause_graph_tracing();
  out:
-        atomic_dec_return(&data->disabled);
         preempt_enable_notrace();
+        unpause_graph_tracing();
 
         return len;
 }
@@ -4955,6 +5037,10 @@ __init static int tracer_alloc_buffers(void)
         if (!alloc_cpumask_var(&tracing_cpumask, GFP_KERNEL))
                 goto out_free_buffer_mask;
 
+        /* Only allocate trace_printk buffers if a trace_printk exists */
+        if (__stop___trace_bprintk_fmt != __start___trace_bprintk_fmt)
+                trace_printk_init_buffers();
+
         /* To save memory, keep the ring buffer size to its minimum */
         if (ring_buffer_expanded)
                 ring_buf_size = trace_buf_size;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 95059f091a24..f9d85504f04b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -826,6 +826,8 @@ extern struct list_head ftrace_events;
 extern const char *__start___trace_bprintk_fmt[];
 extern const char *__stop___trace_bprintk_fmt[];
 
+void trace_printk_init_buffers(void);
+
 #undef FTRACE_ENTRY
 #define FTRACE_ENTRY(call, struct_name, id, tstruct, print, filter)     \
         extern struct ftrace_event_call                                 \
diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
index 6fd4ffd042f9..a9077c1b4ad3 100644
--- a/kernel/trace/trace_printk.c
+++ b/kernel/trace/trace_printk.c
@@ -51,6 +51,10 @@ void hold_module_trace_bprintk_format(const char **start, const char **end)
         const char **iter;
         char *fmt;
 
+        /* allocate the trace_printk per cpu buffers */
+        if (start != end)
+                trace_printk_init_buffers();
+
         mutex_lock(&btrace_mutex);
         for (iter = start; iter < end; iter++) {
                 struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);