cpuidle: tracing: Warn about !rcu_is_watching()
authorPeter Zijlstra <peterz@infradead.org>
Thu, 26 Jan 2023 15:08:32 +0000 (16:08 +0100)
committerIngo Molnar <mingo@kernel.org>
Tue, 31 Jan 2023 14:01:46 +0000 (15:01 +0100)
When using noinstr, WARN when tracing hits when RCU is disabled.

Suggested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230126151323.466670589@infradead.org
include/linux/trace_recursion.h

index c303f7a114e916c6c5a36c7004bace8397b1d28c..d48cd92d2364af67cbc6f4da40a1a1913db4843f 100644 (file)
@@ -135,6 +135,21 @@ extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip);
 # define do_ftrace_record_recursion(ip, pip)   do { } while (0)
 #endif
 
+#ifdef CONFIG_ARCH_WANTS_NO_INSTR
+# define trace_warn_on_no_rcu(ip)                                      \
+       ({                                                              \
+               bool __ret = !rcu_is_watching();                        \
+               if (__ret && !trace_recursion_test(TRACE_RECORD_RECURSION_BIT)) { \
+                       trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \
+                       WARN_ONCE(true, "RCU not on for: %pS\n", (void *)ip); \
+                       trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \
+               }                                                       \
+               __ret;                                                  \
+       })
+#else
+# define trace_warn_on_no_rcu(ip)      false
+#endif
+
 /*
  * Preemption is promised to be disabled when return bit >= 0.
  */
@@ -144,6 +159,9 @@ static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsign
        unsigned int val = READ_ONCE(current->trace_recursion);
        int bit;
 
+       if (trace_warn_on_no_rcu(ip))
+               return -1;
+
        bit = trace_get_context_bit() + start;
        if (unlikely(val & (1 << bit))) {
                /*