[PATCH v2] 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.

v2: Use printk_once()

[ Impact: more information in tracing recursion ]

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
 kernel/trace/ring_buffer.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index b421b0e..e315178 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1495,6 +1495,16 @@ 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%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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