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Subject[PATCH v2 1/2] sched/wait: Add wait_threshold
Date
From: Pavel Begunkov <asml.silence@gmail.com>

Add wait_threshold -- a custom wait_event derivative, that waits until
a value is equal to or greater than the specified threshold.

v2: rebase
1. use full condition instead of event number generator
2. add WQ_THRESHOLD_WAKE_ALWAYS constant

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
include/linux/wait_threshold.h | 67 ++++++++++++++++++++++++++++++++++
kernel/sched/Makefile | 2 +-
kernel/sched/wait_threshold.c | 26 +++++++++++++
3 files changed, 94 insertions(+), 1 deletion(-)
create mode 100644 include/linux/wait_threshold.h
create mode 100644 kernel/sched/wait_threshold.c

diff --git a/include/linux/wait_threshold.h b/include/linux/wait_threshold.h
new file mode 100644
index 000000000000..d8b054504c26
--- /dev/null
+++ b/include/linux/wait_threshold.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_WAIT_THRESHOLD_H
+#define _LINUX_WAIT_THRESHOLD_H
+
+#include <linux/wait.h>
+
+#define WQ_THRESHOLD_WAKE_ALWAYS (~0ui)
+
+struct wait_threshold_queue_entry {
+ struct wait_queue_entry wq_entry;
+ unsigned int threshold;
+};
+
+
+void init_wait_threshold_entry(struct wait_threshold_queue_entry *wtq_entry,
+ unsigned int threshold);
+
+static inline void wake_up_threshold(struct wait_queue_head *wq_head,
+ unsigned int val)
+{
+ void *arg = (void *)(unsigned long)val;
+
+ __wake_up(wq_head, TASK_NORMAL, 1, arg);
+}
+
+#define ___wait_threshold_event(q, thresh, condition, state, \
+ exclusive, ret, cmd) \
+({ \
+ __label__ __out; \
+ struct wait_queue_head *__wq_head = &q; \
+ struct wait_threshold_queue_entry __wtq_entry; \
+ struct wait_queue_entry *__wq_entry = &__wtq_entry.wq_entry; \
+ long __ret = ret; /* explicit shadow */ \
+ \
+ init_wait_threshold_entry(&__wtq_entry, thresh); \
+ for (;;) { \
+ long __int = prepare_to_wait_event(__wq_head, \
+ __wq_entry, \
+ state); \
+ if (condition) \
+ break; \
+ \
+ if (___wait_is_interruptible(state) && __int) { \
+ __ret = __int; \
+ goto __out; \
+ } \
+ \
+ cmd; \
+ } \
+ finish_wait(__wq_head, __wq_entry); \
+__out: __ret; \
+})
+
+#define __wait_threshold_interruptible(q, thresh, condition) \
+ ___wait_threshold_event(q, thresh, condition, TASK_INTERRUPTIBLE, 0, 0,\
+ schedule())
+
+#define wait_threshold_interruptible(q, threshold, condition) \
+({ \
+ int __ret = 0; \
+ might_sleep(); \
+ if (!(condition)) \
+ __ret = __wait_threshold_interruptible(q, \
+ threshold, condition); \
+ __ret; \
+})
+#endif /* _LINUX_WAIT_THRESHOLD_H */
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 21fb5a5662b5..bb895a3184f9 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -18,7 +18,7 @@ endif

obj-y += core.o loadavg.o clock.o cputime.o
obj-y += idle.o fair.o rt.o deadline.o
-obj-y += wait.o wait_bit.o swait.o completion.o
+obj-y += wait.o wait_bit.o wait_threshold.o swait.o completion.o

obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o pelt.o
obj-$(CONFIG_SCHED_AUTOGROUP) += autogroup.o
diff --git a/kernel/sched/wait_threshold.c b/kernel/sched/wait_threshold.c
new file mode 100644
index 000000000000..80a027c02ff3
--- /dev/null
+++ b/kernel/sched/wait_threshold.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include "sched.h"
+#include <linux/wait_threshold.h>
+
+static int wake_threshold_function(struct wait_queue_entry *wq_entry,
+ unsigned int mode, int sync, void *arg)
+{
+ unsigned int val = (unsigned int)(unsigned long)arg;
+ struct wait_threshold_queue_entry *wtq_entry =
+ container_of(wq_entry, struct wait_threshold_queue_entry,
+ wq_entry);
+
+ if (val < wtq_entry->threshold)
+ return 0;
+
+ return default_wake_function(wq_entry, mode, sync, arg);
+}
+
+void init_wait_threshold_entry(struct wait_threshold_queue_entry *wtq_entry,
+ unsigned int threshold)
+{
+ init_wait_entry(&wtq_entry->wq_entry, 0);
+ wtq_entry->wq_entry.func = wake_threshold_function;
+ wtq_entry->threshold = threshold;
+}
+EXPORT_SYMBOL(init_wait_threshold_entry);
--
2.23.0
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