Fix: rcu: Fix data-race due to atomic_t copy-by-value (5.5.6, 5.4.22)

The following upstream commit has been backported to stable kernels
5.5.6 and 5.4.22:

  commit 6cf539a87a61a4fbc43f625267dbcbcf283872ed
  Author: Marco Elver <elver@google.com>
  Date:   Wed Oct 9 17:57:43 2019 +0200

    rcu: Fix data-race due to atomic_t copy-by-value

    This fixes a data-race where `atomic_t dynticks` is copied by value. The
    copy is performed non-atomically, resulting in a data-race if `dynticks`
    is updated concurrently.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/instrumentation/events/lttng-module/rcu.h b/instrumentation/events/lttng-module/rcu.h
index 5faaaa63d96f1ef6700e2ed2c6b2f04c927768c0..6bb941f99ca2ccdc02ac297504f2d40b84fb8c2a 100644 (file)
--- a/instrumentation/events/lttng-module/rcu.h
+++ b/instrumentation/events/lttng-module/rcu.h
@@ -386,7 +386,9 @@ LTTNG_TRACEPOINT_EVENT(rcu_fqs,
  * events use the upper bits of each number, while interrupt-related
  * events use the lower bits.
  */
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,6,0))
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,6,0))      \
+       || LTTNG_KERNEL_RANGE(5,5,6, 5,6,0)             \
+       || LTTNG_KERNEL_RANGE(5,4,22, 5,5,0)
 LTTNG_TRACEPOINT_EVENT(rcu_dyntick,
 
        TP_PROTO(const char *polarity, long oldnesting, long newnesting, int dynticks),