linux-kernel - [PATCH v9 35/37] tracing: Increase trace_recursive

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Message-Id: <827fcc7a6840db06d196fc18905033d519681eff.1516069914.git.tom.zanussi@linux.intel.com>
Date:   Mon, 15 Jan 2018 20:52:09 -0600
From:   Tom Zanussi <tom.zanussi@...ux.intel.com>
To:     rostedt@...dmis.org
Cc:     tglx@...utronix.de, mhiramat@...nel.org, namhyung@...nel.org,
        vedang.patel@...el.com, bigeasy@...utronix.de,
        joel.opensrc@...il.com, joelaf@...gle.com,
        mathieu.desnoyers@...icios.com, baohong.liu@...el.com,
        rajvi.jingar@...el.com, julia@...com, fengguang.wu@...el.com,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [PATCH v9 35/37] tracing: Increase trace_recursive_lock() limit for synthetic events

Synthetic event generation needs to happen while the current event is
still in progress, so add 1 to the trace_recursive_lock() recursion
limit to account for that.

Because we also want to allow for the possibility of a synthetic event
being generated from another synthetic event, add an additional
increment for that as well.

Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
---
 kernel/trace/ring_buffer.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 48c0619..ca2ffc9 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2585,16 +2585,16 @@ static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
  *  IRQ context
  *  NMI context
  *
- * If for some reason the ring buffer starts to recurse, we
- * only allow that to happen at most 4 times (one for each
- * context). If it happens 5 times, then we consider this a
- * recusive loop and do not let it go further.
+ * If for some reason the ring buffer starts to recurse, we only allow
+ * that to happen at most 6 times (one for each context, plus possibly
+ * two levels of synthetic event generation). If it happens 7 times,
+ * then we consider this a recusive loop and do not let it go further.
  */
 
 static __always_inline int
 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
 {
-	if (cpu_buffer->current_context >= 4)
+	if (cpu_buffer->current_context >= 6)
 		return 1;
 
 	cpu_buffer->current_context++;
-- 
1.9.3