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2023-12-09 b22da3d8526a935aa31e086e63f60ff3246cb61c

 kernel/include/linux/once.h
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@@ -5,9 +5,17 @@
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 #include <linux/types.h>
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 #include <linux/jump_label.h>
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+/* Helpers used from arbitrary contexts.
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+ * Hard irqs are blocked, be cautious.
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+ */
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 bool __do_once_start(bool *done, unsigned long *flags);
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 void __do_once_done(bool *done, struct static_key_true *once_key,
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-		    unsigned long *flags, struct module *mod);
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+		    unsigned long *flags);
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+
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+/* Variant for process contexts only. */
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+bool __do_once_slow_start(bool *done);
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+void __do_once_slow_done(bool *done, struct static_key_true *once_key,
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+			 struct module *mod);
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 /* Call a function exactly once. The idea of DO_ONCE() is to perform
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  * a function call such as initialization of random seeds, etc, only
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@@ -46,7 +54,24 @@
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 			if (unlikely(___ret)) {				     \
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 				func(__VA_ARGS__);			     \
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 				__do_once_done(&___done, &___once_key,	     \
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-					       &___flags, THIS_MODULE);	     \
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+					       &___flags);		     \
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+			}						     \
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+		}							     \
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+		___ret;							     \
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+	})
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+
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+/* Variant of DO_ONCE() for process/sleepable contexts. */
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+#define DO_ONCE_SLOW(func, ...)						     \
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+	({								     \
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+		bool ___ret = false;					     \
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+		static bool __section(".data.once") ___done = false;	     \
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+		static DEFINE_STATIC_KEY_TRUE(___once_key);		     \
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+		if (static_branch_unlikely(&___once_key)) {		     \
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+			___ret = __do_once_slow_start(&___done);	     \
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+			if (unlikely(___ret)) {				     \
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+				func(__VA_ARGS__);			     \
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+				__do_once_slow_done(&___done, &___once_key,  \
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+						    THIS_MODULE);	     \
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 			}						     \
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 		}							     \
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 		___ret;							     \
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@@ -57,4 +82,7 @@
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 #define get_random_once_wait(buf, nbytes)                                    \
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 	DO_ONCE(get_random_bytes_wait, (buf), (nbytes))                      \
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+#define get_random_slow_once(buf, nbytes)				     \
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+	DO_ONCE_SLOW(get_random_bytes, (buf), (nbytes))
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+
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 #endif /* _LINUX_ONCE_H */