tracing/core: Add current context on tracing recursion warning

In case of tracing recursion detection, we only get the stacktrace.
But the current context may be very useful to debug the issue.

This patch adds the softirq/hardirq/nmi context with the warning
using lockdep context display to have a familiar output.

v2: Use printk_once()
v3: drop {hardirq,softirq}_context which depend on lockdep,
    only keep what is part of current->trace_recursion,
    sufficient to debug the warning source.

[ Impact: print context necessary to debug recursion ]

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

kernel/trace/ring_buffer.c

@@ -1495,6 +1495,13 @@ static int trace_recursive_lock(void)
 	if (unlikely(current->trace_recursion & (1 << level))) {
 		/* Disable all tracing before we do anything else */
 		tracing_off_permanent();
+
+		printk_once(KERN_WARNING "Tracing recursion: "
+			    "HC[%lu]:SC[%lu]:NMI[%lu]\n",
+			    hardirq_count() >> HARDIRQ_SHIFT,
+			    softirq_count() >> SOFTIRQ_SHIFT,
+			    in_nmi());
+
 		WARN_ON_ONCE(1);
 		return -1;
 	}