tracing: use raw spinlocks for trace_vprintk

Impact: prevent locking up by lockdep tracer

The lockdep tracer uses trace_vprintk and thus trace_vprintk can not
call back into lockdep without locking up.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8c6a902..4c97947 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1176,7 +1176,8 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
  */
 int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
 {
-       static DEFINE_SPINLOCK(trace_buf_lock);
+       static raw_spinlock_t trace_buf_lock =
+               (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
        static u32 trace_buf[TRACE_BUF_SIZE];
 
        struct ring_buffer_event *event;
@@ -1201,7 +1202,9 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
        if (unlikely(atomic_read(&data->disabled)))
                goto out;
 
-       spin_lock_irqsave(&trace_buf_lock, flags);
+       /* Lockdep uses trace_printk for lock tracing */
+       local_irq_save(flags);
+       __raw_spin_lock(&trace_buf_lock);
        len = vbin_printf(trace_buf, TRACE_BUF_SIZE, fmt, args);
 
        if (len > TRACE_BUF_SIZE || len < 0)
@@ -1220,7 +1223,8 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
        ring_buffer_unlock_commit(tr->buffer, event);
 
 out_unlock:
-       spin_unlock_irqrestore(&trace_buf_lock, flags);
+       __raw_spin_unlock(&trace_buf_lock);
+       local_irq_restore(flags);
 
 out:
        ftrace_preempt_enable(resched);