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hc

2023-12-08 01573e231f18eb2d99162747186f59511f56b64d

 kernel/include/linux/swait.h
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@@ -9,23 +9,10 @@
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 #include <asm/current.h>
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 /*
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- * BROKEN wait-queues.
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- *
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- * These "simple" wait-queues are broken garbage, and should never be
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- * used. The comments below claim that they are "similar" to regular
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- * wait-queues, but the semantics are actually completely different, and
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- * every single user we have ever had has been buggy (or pointless).
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- *
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- * A "swake_up_one()" only wakes up _one_ waiter, which is not at all what
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- * "wake_up()" does, and has led to problems. In other cases, it has
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- * been fine, because there's only ever one waiter (kvm), but in that
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- * case gthe whole "simple" wait-queue is just pointless to begin with,
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- * since there is no "queue". Use "wake_up_process()" with a direct
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- * pointer instead.
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- *
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- * While these are very similar to regular wait queues (wait.h) the most
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- * important difference is that the simple waitqueue allows for deterministic
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- * behaviour -- IOW it has strictly bounded IRQ and lock hold times.
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+ * Simple waitqueues are semantically very different to regular wait queues
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+ * (wait.h). The most important difference is that the simple waitqueue allows
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+ * for deterministic behaviour -- IOW it has strictly bounded IRQ and lock hold
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+ * times.
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  *
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  * Mainly, this is accomplished by two things. Firstly not allowing swake_up_all
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  * from IRQ disabled, and dropping the lock upon every wakeup, giving a higher
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@@ -39,7 +26,7 @@
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  *    sleeper state.
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  *
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  *  - the !exclusive mode; because that leads to O(n) wakeups, everything is
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- *    exclusive.
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+ *    exclusive. As such swake_up_one will only ever awake _one_ waiter.
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  *
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  *  - custom wake callback functions; because you cannot give any guarantees
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  *    about random code. This also allows swait to be used in RT, such that
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@@ -160,9 +147,7 @@
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 extern void swake_up_one(struct swait_queue_head *q);
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 extern void swake_up_all(struct swait_queue_head *q);
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 extern void swake_up_locked(struct swait_queue_head *q);
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-extern void swake_up_all_locked(struct swait_queue_head *q);
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-extern void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
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 extern void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state);
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 extern long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state);
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@@ -298,19 +283,5 @@
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 						   condition, timeout);	\
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 	__ret;								\
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 })
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-
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-#define __swait_event_lock_irq(wq, condition, lock, cmd)		\
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-	___swait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0,		\
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-		       raw_spin_unlock_irq(&lock);			\
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-		       cmd;						\
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-		       schedule();					\
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-		       raw_spin_lock_irq(&lock))
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-
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-#define swait_event_lock_irq(wq_head, condition, lock)			\
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-	do {								\
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-		if (condition)						\
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-			break;						\
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-		__swait_event_lock_irq(wq_head, condition, lock, );	\
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-	} while (0)
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 #endif /* _LINUX_SWAIT_H */