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-rw-r--r--include/linux/cookie.h51
1 files changed, 51 insertions, 0 deletions
diff --git a/include/linux/cookie.h b/include/linux/cookie.h
new file mode 100644
index 000000000000..0c159f585109
--- /dev/null
+++ b/include/linux/cookie.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_COOKIE_H
+#define __LINUX_COOKIE_H
+
+#include <linux/atomic.h>
+#include <linux/percpu.h>
+#include <asm/local.h>
+
+struct pcpu_gen_cookie {
+ local_t nesting;
+ u64 last;
+} __aligned(16);
+
+struct gen_cookie {
+ struct pcpu_gen_cookie __percpu *local;
+ atomic64_t forward_last ____cacheline_aligned_in_smp;
+ atomic64_t reverse_last;
+};
+
+#define COOKIE_LOCAL_BATCH 4096
+
+#define DEFINE_COOKIE(name) \
+ static DEFINE_PER_CPU(struct pcpu_gen_cookie, __##name); \
+ static struct gen_cookie name = { \
+ .local = &__##name, \
+ .forward_last = ATOMIC64_INIT(0), \
+ .reverse_last = ATOMIC64_INIT(0), \
+ }
+
+static __always_inline u64 gen_cookie_next(struct gen_cookie *gc)
+{
+ struct pcpu_gen_cookie *local = this_cpu_ptr(gc->local);
+ u64 val;
+
+ if (likely(local_inc_return(&local->nesting) == 1)) {
+ val = local->last;
+ if (__is_defined(CONFIG_SMP) &&
+ unlikely((val & (COOKIE_LOCAL_BATCH - 1)) == 0)) {
+ s64 next = atomic64_add_return(COOKIE_LOCAL_BATCH,
+ &gc->forward_last);
+ val = next - COOKIE_LOCAL_BATCH;
+ }
+ local->last = ++val;
+ } else {
+ val = atomic64_dec_return(&gc->reverse_last);
+ }
+ local_dec(&local->nesting);
+ return val;
+}
+
+#endif /* __LINUX_COOKIE_H */