Provide atomic load and store functions for int and long. FreeBSD

also uses these names.  This implements a complete interface for
atomic operations, such functions can be used for every access.
They provide compiler barriers, but no CPU memory barriers.  This
is consistent with our other atomic operations.
OK mvs@ visa@

diff --git a/distrib/sets/lists/comp/mi b/distrib/sets/lists/comp/mi
index fdd5ac3..52bf33e 100644 (file)
--- a/distrib/sets/lists/comp/mi
+++ b/distrib/sets/lists/comp/mi
@@ -3046,6 +3046,7 @@
 ./usr/share/man/man9/atomic_cas_uint.9
 ./usr/share/man/man9/atomic_dec_int.9
 ./usr/share/man/man9/atomic_inc_int.9
+./usr/share/man/man9/atomic_load_int.9
 ./usr/share/man/man9/atomic_setbits_int.9
 ./usr/share/man/man9/atomic_sub_int.9
 ./usr/share/man/man9/atomic_swap_uint.9

diff --git a/share/man/man9/atomic_load_int.9 b/share/man/man9/atomic_load_int.9
new file mode 100644 (file)
index 0000000..a9b9784
--- /dev/null
+++ b/share/man/man9/atomic_load_int.9
@@ -0,0 +1,68 @@
+.\" $OpenBSD: atomic_load_int.9,v 1.1 2022/03/10 14:12:40 bluhm Exp $
+.\"
+.\" Copyright (c) 2014 David Gwynne <dlg@openbsd.org>
+.\" Copyright (c) 2022 Alexander Bluhm <bluhm@openbsd.org>
+.\" All rights reserved.
+.\"
+.\" Permission to use, copy, modify, and distribute this software for any
+.\" purpose with or without fee is hereby granted, provided that the above
+.\" copyright notice and this permission notice appear in all copies.
+.\"
+.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.\"
+.Dd $Mdocdate: March 10 2022 $
+.Dt ATOMIC_LOAD_INT 9
+.Os
+.Sh NAME
+.Nm atomic_load_int ,
+.Nm atomic_load_long ,
+.Nm atomic_store_long ,
+.Nm atomic_store_int
+.Nd atomic read and write memory operations
+.Sh SYNOPSIS
+.In sys/atomic.h
+.Ft unsigned int
+.Fn atomic_load_int "volatile unsigned int *p"
+.Ft unsigned long
+.Fn atomic_load_long "volatile unsigned long *p"
+.Ft void
+.Fn atomic_store_int "volatile unsigned int *p" "unsigned int v"
+.Ft void
+.Fn atomic_store_long "volatile unsigned long *p" "unsigned long v"
+.Sh DESCRIPTION
+The atomic_load and atomic_store set of functions provide an interface
+for atomically performing read or write memory operations with
+respect to interrupts and multiple processors in the system.
+.Pp
+The atomic_store functions change the value referenced by the pointer
+.Fa p
+to the value
+.Fa v .
+.Sh CONTEXT
+.Fn atomic_load_int ,
+.Fn atomic_load_long ,
+.Fn atomic_store_int ,
+and
+.Fn atomic_store_long
+can all be called during autoconf, from process context, or from
+interrupt context.
+.Sh RETURN VALUES
+.Nm atomic_load_int
+and
+.Nm atomic_load_long
+return the value at
+.Fa p .
+.Sh SEE ALSO
+.Xr atomic_add_int 9 ,
+.Xr atomic_add_long 9 ,
+.Xr atomic_sub_int 9 ,
+.Xr atomic_sub_long 9
+.Sh HISTORY
+The atomic_load and atomic_store functions first appeared in
+.Ox 7.1 .

diff --git a/sys/sys/atomic.h b/sys/sys/atomic.h
index 22b92b6..71869bc 100644 (file)
--- a/sys/sys/atomic.h
+++ b/sys/sys/atomic.h
@@ -1,6 +1,7 @@
-/*     $OpenBSD: atomic.h,v 1.6 2019/03/09 06:14:21 visa Exp $ */
+/*     $OpenBSD: atomic.h,v 1.7 2022/03/10 14:12:40 bluhm Exp $ */
 /*
  * Copyright (c) 2014 David Gwynne <dlg@openbsd.org>
+ * Copyright (c) 2022 Alexander Bluhm <bluhm@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -195,6 +196,50 @@ atomic_sub_long_nv(volatile unsigned long *p, unsigned long v)
 #define atomic_dec_long(_p) ((void)atomic_dec_long_nv(_p))
 #endif
 
+#ifdef _KERNEL
+/*
+ * atomic_load_* - read from memory
+ */
+
+static void membar_datadep_consumer(void);
+
+static inline unsigned int
+atomic_load_int(volatile unsigned int *p)
+{
+       unsigned int v;
+
+       v = *p;
+       membar_datadep_consumer();
+       return v;
+}
+
+static inline unsigned long
+atomic_load_long(volatile unsigned long *p)
+{
+       unsigned long v;
+
+       v = *p;
+       membar_datadep_consumer();
+       return v;
+}
+
+/*
+ * atomic_store_* - write to memory
+ */
+
+static inline void
+atomic_store_int(volatile unsigned int *p, unsigned int v)
+{
+       *p = v;
+}
+
+static inline void
+atomic_store_long(volatile unsigned long *p, unsigned long v)
+{
+       *p = v;
+}
+#endif /* _KERNEL */
+
 /*
  * memory barriers
  */