docs: man: Add spinlock(9)

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 71 insertions, 0 deletions

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+.\" Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions are met:
+.\"
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+.\"    this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
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+.\"
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+.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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+.Dd Dec 16 2024
+.Dt SPINLOCK 9
+.Os Hyra
+.Sh NAME
+.Nm spinlock - generic spinlock for syncronization
+.Sh SYNOPSIS
+.In sys/spinlock.h
+
+.Ft void
+.Fn spinlock_acquire "struct spinlock *lock"
+.Ft void
+.Fn spinlock_release "struct spinlock *lock"
+.Ft int
+.Fn spinlock_usleep "struct spinlock *lock" "size_t usec_max"
+.Sh DESCRIPTION
+
+The set of functions provide a simple spin-based locking mechanism
+to ensure mutual exclusion between threads.
+
+The
+.Ft spinlock_acquire
+function is used to acquire a spinlock pointed to by
+.Fa lock .
+If the lock is unavailable (being held by another thread), it
+will wait until the lock owner releases it.
+
+The
+.Ft spinlock_release
+function is used to release a spinlock pointed to by
+.Fa lock .
+This allows other threads to hold it.
+
+The
+.Ft spinlock_usleep
+function attempts to acquire a spinlock pointed to by
+.Fa lock .
+If the lock is unavailable, it waits up to a maximum
+duration of
+.Fa usec_max
+microseconds. If the lock is still being held, it will return
+a non-zero value indicating a timeout. If the lock is successfully
+acquired, a value of 0 is returned.
+
+.Sh AUTHORS
+.An Ian Moffett Aq Mt ian@osmora.org