[PATCH] tracing/core: Add current context on tracing recursion warning

[Frederic Weisbecker]

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.

[ Impact: more information in tracing recursion ]

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
 kernel/trace/ring_buffer.c |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index b421b0e..27a6e7d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1493,8 +1493,21 @@ static int trace_recursive_lock(void)
 	level = trace_irq_level();
 
 	if (unlikely(current->trace_recursion & (1 << level))) {
+		static atomic_t warned;
+
 		/* Disable all tracing before we do anything else */
 		tracing_off_permanent();
+
+		if (atomic_inc_return(&warned) == 1) {
+			printk(KERN_WARNING "Tracing recursion: "
+				"[HC%u[%lu]:SC%u[%lu]:NMI[%lu]:HE%u:SE%u]\n",
+				current->hardirq_context,
+				hardirq_count() >> HARDIRQ_SHIFT,
+				current->softirq_context,
+				softirq_count() >> SOFTIRQ_SHIFT,
+				in_nmi(), current->hardirqs_enabled,
+				current->softirqs_enabled);
+		}
 		WARN_ON_ONCE(1);
 		return -1;
 	}
-- 
1.6.1


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