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-rw-r--r--include/linux/once.h28
1 files changed, 28 insertions, 0 deletions
diff --git a/include/linux/once.h b/include/linux/once.h
index b14d8b309d52..bc714d414448 100644
--- a/include/linux/once.h
+++ b/include/linux/once.h
@@ -5,10 +5,18 @@
#include <linux/types.h>
#include <linux/jump_label.h>
+/* Helpers used from arbitrary contexts.
+ * Hard irqs are blocked, be cautious.
+ */
bool __do_once_start(bool *done, unsigned long *flags);
void __do_once_done(bool *done, struct static_key_true *once_key,
unsigned long *flags, struct module *mod);
+/* Variant for process contexts only. */
+bool __do_once_sleepable_start(bool *done);
+void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
+ struct module *mod);
+
/* Call a function exactly once. The idea of DO_ONCE() is to perform
* a function call such as initialization of random seeds, etc, only
* once, where DO_ONCE() can live in the fast-path. After @func has
@@ -52,7 +60,27 @@ void __do_once_done(bool *done, struct static_key_true *once_key,
___ret; \
})
+/* Variant of DO_ONCE() for process/sleepable contexts. */
+#define DO_ONCE_SLEEPABLE(func, ...) \
+ ({ \
+ bool ___ret = false; \
+ static bool __section(".data.once") ___done = false; \
+ static DEFINE_STATIC_KEY_TRUE(___once_key); \
+ if (static_branch_unlikely(&___once_key)) { \
+ ___ret = __do_once_sleepable_start(&___done); \
+ if (unlikely(___ret)) { \
+ func(__VA_ARGS__); \
+ __do_once_sleepable_done(&___done, &___once_key,\
+ THIS_MODULE); \
+ } \
+ } \
+ ___ret; \
+ })
+
#define get_random_once(buf, nbytes) \
DO_ONCE(get_random_bytes, (buf), (nbytes))
+#define get_random_sleepable_once(buf, nbytes) \
+ DO_ONCE_SLEEPABLE(get_random_bytes, (buf), (nbytes))
+
#endif /* _LINUX_ONCE_H */