2 files changed, 46 insertions, 11 deletions
diff --git a/share/man/man9/VFS.9 b/share/man/man9/VFS.9
index a1d0a19bec13..6ea6570bbf6e 100644
--- a/share/man/man9/VFS.9
+++ b/share/man/man9/VFS.9
@@ -26,7 +26,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd February 9, 2010
+.Dd November 3, 2025
 .Dt VFS 9
 .Os
 .Sh NAME
@@ -42,6 +42,7 @@ function from
 rather than implementing empty functions or casting to
 .Fa eopnotsupp .
 .Sh SEE ALSO
+.Xr dtrace_vfs 4 ,
 .Xr VFS_CHECKEXP 9 ,
 .Xr VFS_FHTOVP 9 ,
 .Xr VFS_MOUNT 9 ,
diff --git a/share/man/man9/atomic.9 b/share/man/man9/atomic.9
index c9133c6311a5..b027a0ff0bca 100644
--- a/share/man/man9/atomic.9
+++ b/share/man/man9/atomic.9
@@ -182,35 +182,42 @@ This variant is the default.
 The second variant has acquire semantics, and the third variant has release
 semantics.
 .Pp
-When an atomic operation has acquire semantics, the operation must have
+An atomic operation can only have
+.Em acquire
+semantics if it performs a load
+from memory.
+When an atomic operation has acquire semantics, a load performed as
+part of the operation must have
 completed before any subsequent load or store (by program order) is
 performed.
 Conversely, acquire semantics do not require that prior loads or stores have
-completed before the atomic operation is performed.
-An atomic operation can only have acquire semantics if it performs a load
-from memory.
+completed before a load from the atomic operation is performed.
 To denote acquire semantics, the suffix
 .Dq Li _acq
 is inserted into the function name immediately prior to the
 .Dq Li _ Ns Aq Fa type
 suffix.
-For example, to subtract two integers ensuring that the subtraction is
+For example, to subtract two integers ensuring that the load of
+the value from memory is
 completed before any subsequent loads and stores are performed, use
 .Fn atomic_subtract_acq_int .
 .Pp
+An atomic operation can only have
+.Em release
+semantics if it performs a store to memory.
 When an atomic operation has release semantics, all prior loads or stores
-(by program order) must have completed before the operation is performed.
-Conversely, release semantics do not require that the atomic operation must
+(by program order) must have completed before a store executed as part of
+the operation that is performed.
+Conversely, release semantics do not require that a store from the atomic
+operation must
 have completed before any subsequent load or store is performed.
-An atomic operation can only have release semantics if it performs a store
-to memory.
 To denote release semantics, the suffix
 .Dq Li _rel
 is inserted into the function name immediately prior to the
 .Dq Li _ Ns Aq Fa type
 suffix.
 For example, to add two long integers ensuring that all prior loads and
-stores are completed before the addition is performed, use
+stores are completed before the store of the result is performed, use
 .Fn atomic_add_rel_long .
 .Pp
 When a release operation by one thread
@@ -235,6 +242,33 @@ section.
 However, they will not prevent the compiler or processor from moving loads
 or stores into the critical section, which does not violate the semantics of
 a mutex.
+.Ss Architecture-dependent caveats for compare-and-swap
+The
+.Fn atomic_[f]cmpset_<type>
+operations, specifically those without explicitly specified memory
+ordering, are defined as relaxed.
+Consequently, a thread's accesses to memory locations different from
+that of the atomic operation can be reordered in relation to the
+atomic operation.
+.Pp
+However, the implementation on the
+.Sy amd64
+and
+.Sy i386
+architectures provide sequentially consistent semantics.
+In particular, the reordering mentioned above cannot occur.
+.Pp
+On the
+.Sy arm64/aarch64
+architecture, the operation may include either acquire
+semantics on the constituent load or release semantics
+on the constituent store.
+This means that accesses to other locations in program order
+before the atomic, might be observed as executed after the load
+that is the part of the atomic operation (but not after the store
+from the operation due to release).
+Similarly, accesses after the atomic might be observed as executed
+before the store.
 .Ss Thread Fence Operations
 Alternatively, a programmer can use atomic thread fence operations to
 constrain the reordering of accesses.