> Date: Thu, 10 Mar 2022 21:53:13 +0100 > From: Alexander Bluhm <[email protected]> > > Hi, > > claudio@ mentioned that documentation for membar_enter_after_atomic > and membar_exit_before_atomic is missing. > > ok?
I think this is fine, although it doesn't actually define what an "atomic operation" is in this context. Now we we only actually provide an optimized implementation on x86; on all other architectures that we support, these are just aliases for membar_enter() and membar_exit(). So all x86 operations that perform a bus lock are supported. However the atomic_load_xxx() and atomic_store_xxx() operations you just introduced do not fall into this category. Not sure if that needs spelling out. And if it does, maybe the chosen names for those functions are wrong? > Index: membar_sync.9 > =================================================================== > RCS file: /data/mirror/openbsd/cvs/src/share/man/man9/membar_sync.9,v > retrieving revision 1.3 > diff -u -p -r1.3 membar_sync.9 > --- membar_sync.9 14 Feb 2014 05:11:55 -0000 1.3 > +++ membar_sync.9 10 Mar 2022 20:51:01 -0000 > @@ -35,7 +35,9 @@ > .Nm membar_exit , > .Nm membar_producer , > .Nm membar_consumer , > -.Nm membar_sync > +.Nm membar_sync , > +.Nm membar_enter_after_atomic , > +.Nm membar_exit_before_atomic > .Nd memory access barrier operations > .Sh SYNOPSIS > .In sys/atomic.h > @@ -49,6 +51,10 @@ > .Fn membar_consumer "void" > .Ft void > .Fn membar_sync "void" > +.Ft void > +.Fn membar_enter_after_atomic "void" > +.Ft void > +.Fn membar_exit_before_atomic "void" > .Sh DESCRIPTION > The membar set of functions provide an interface for issuing memory barrier > access operations with respect to multiple processors in the system. > @@ -79,14 +85,27 @@ after the memory barrier complete. > All loads and stores preceding the memory barrier will complete and > reach global visibility before any loads and stores after the memory > barrier complete and reach global visibility. > +.It Fn membar_enter_after_atomic > +An atomic operation preceding > +.Fn membar_enter_after_atomic > +will reach global visibility before all loads and stores following it. > +The atomic operation is used to protect the start of a critical section. > +.It Fn membar_exit_before_atomic > +All loads and stores preceding > +.Fn membar_exit_before_atomic > +will reach global visibility before atomic operation that follows it. > +The atomic operation is used to protect the end of a critical section. > .El > .Sh CONTEXT > .Fn membar_enter , > .Fn membar_exit , > .Fn membar_producer , > .Fn membar_consumer , > -.Fn membar_sync > -can all be called during autoconf, from process context, or from interrupt > context. > +.Fn membar_sync , > +.Fn membar_enter_after_atomic , > +.Fn membar_exit_before_atomic > +can all be called during autoconf, from process context, or from > +interrupt context. > .Sh HISTORY > The membar functions first appeared in > .Nx 5.0 > >
