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19e18e6dab
[ Upstream commit5f1ef0dfcb] A bug was reported about an infinite recursion caused by tracing the rcu events with the kernel stack trace trigger enabled. The stack trace code called back into RCU which then called the stack trace again. Expand the ftrace recursion protection to add a set of bits to protect events from recursion. Each bit represents the context that the event is in (normal, softirq, interrupt and NMI). Have the stack trace code use the interrupt context to protect against recursion. Note, the bug showed an issue in both the RCU code as well as the tracing stacktrace code. This only handles the tracing stack trace side of the bug. The RCU fix will be handled separately. Link: https://lore.kernel.org/all/20260102122807.7025fc87@gandalf.local.home/ Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Boqun Feng <boqun.feng@gmail.com> Link: https://patch.msgid.link/20260105203141.515cd49f@gandalf.local.home Reported-by: Yao Kai <yaokai34@huawei.com> Tested-by: Yao Kai <yaokai34@huawei.com> Fixes:5f5fa7ea89("rcu: Don't use negative nesting depth in __rcu_read_unlock()") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Leon Chen <leonchen.oss@139.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>