Hook up printk() with sched_trace.c.

2 files changed, 19 insertions, 1 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 89011bf8c106..4423a5542eef 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -54,6 +54,13 @@ int console_printk[4] = {
         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
 };
 
+/* divert printk() messages when we have a LITMUS^RT
+ * debug listener
+ */
+#include <litmus/litmus.h>
+int trace_override = 0;
+int trace_recurse  = 0;
+
 /*
  * Low level drivers may need that to know if they can schedule in
  * their unblank() callback or not. So let's export it.
@@ -652,6 +659,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 
         /* Emit the output into the temporary buffer */
         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
+        if (trace_override && !trace_recurse)
+                TRACE("%s", printk_buf);
 
         /*
          * Copy the output into log_buf.  If the caller didn't provide
@@ -932,7 +941,7 @@ int is_console_locked(void)
 
 void wake_up_klogd(void)
 {
-        if (!oops_in_progress && waitqueue_active(&log_wait))
+        if (!trace_override && !oops_in_progress && waitqueue_active(&log_wait))
                 wake_up_interruptible(&log_wait);
 }
 
diff --git a/litmus/sched_trace.c b/litmus/sched_trace.c
index 8581c03bb137..9ee6f02a61d8 100644
--- a/litmus/sched_trace.c
+++ b/litmus/sched_trace.c
@@ -301,6 +301,10 @@ static ssize_t log_read(struct file *filp, char __user *to, size_t len,
 
 
 
+/* in kernel/printk.c */
+extern int trace_override;
+extern int trace_recurse;
+
 
 /* log_open - open the global log message ring buffer.
  */
@@ -330,6 +334,7 @@ static int log_open(struct inode *in, struct file *filp)
         printk(KERN_DEBUG "sched_trace buf: from 0x%p to 0x%p  length: %x\n",
                buf->buf.buf, buf->buf.end,
                (unsigned int) (buf->buf.end - buf->buf.buf));
+        trace_override++;
  out_unlock:
         up(&buf->reader_mutex);
  out:
@@ -353,6 +358,7 @@ static int log_release(struct inode *in, struct file *filp)
                 error = rb_free_buf(&buf->buf);
         }
 
+        trace_override--;
         up(&buf->reader_mutex);
  out:
         return error;
@@ -490,9 +496,12 @@ void dump_trace_buffer(int max)
         int len;
         int count = 0;
 
+        /* potential but very unlikely race... */
+        trace_recurse = 1;
         while ((max == 0 || count++ < max) &&
                (len = rb_get(&log_buffer.buf, line, sizeof(line) - 1)) > 0) {
                 line[len] = '\0';
                 printk("%s", line);
         }
+        trace_recurse = 0;
 }