search for: smp_store_pointer

On Tue, Dec 05, 2017 at 11:24:49PM +0200, Michael S. Tsirkin wrote: > READ_ONCE is really all over the place (some code literally replaced all > memory accesses with READ/WRITE ONCE). Yeah, so? Complain to the compiler people for forcing us into that. > Would an API like WRITE_POINTER()/smp_store_pointer make sense, > and READ_POINTER for symmetry? No, the whole point of the exercise was to get away from the fact that dependent loads are special.

On Tue, Dec 05, 2017 at 11:24:49PM +0200, Michael S. Tsirkin wrote: > READ_ONCE is really all over the place (some code literally replaced all > memory accesses with READ/WRITE ONCE). Yeah, so? Complain to the compiler people for forcing us into that. > Would an API like WRITE_POINTER()/smp_store_pointer make sense, > and READ_POINTER for symmetry? No, the whole point of the exercise was to get away from the fact that dependent loads are special.

On Tue, Dec 05, 2017 at 09:51:48PM +0200, Michael S. Tsirkin wrote: > On Tue, Dec 05, 2017 at 11:33:39AM -0800, Paul E. McKenney wrote: > > On Tue, Dec 05, 2017 at 09:24:21PM +0200, Michael S. Tsirkin wrote: [ . . . ] > > > and this barrier is no longer paired with anything until > > > you realize there's a dependency barrier within READ_ONCE. > > > >

On Tue, Dec 05, 2017 at 09:51:48PM +0200, Michael S. Tsirkin wrote: > On Tue, Dec 05, 2017 at 11:33:39AM -0800, Paul E. McKenney wrote: > > On Tue, Dec 05, 2017 at 09:24:21PM +0200, Michael S. Tsirkin wrote: [ . . . ] > > > and this barrier is no longer paired with anything until > > > you realize there's a dependency barrier within READ_ONCE. > > > >

...be paired with > > the new improved READ_ONCE()? > > READ_ONCE is really all over the place (some code literally replaced all > memory accesses with READ/WRITE ONCE). > > And I also prefer smp_wmb as it seems to be cheaper on ARM. > > Would an API like WRITE_POINTER()/smp_store_pointer make sense, > and READ_POINTER for symmetry? What we do in some code is to comment the pairings, allowing the other side of the pairing to be easily located. Would that work for you? Thanx, Paul

...be paired with > > the new improved READ_ONCE()? > > READ_ONCE is really all over the place (some code literally replaced all > memory accesses with READ/WRITE ONCE). > > And I also prefer smp_wmb as it seems to be cheaper on ARM. > > Would an API like WRITE_POINTER()/smp_store_pointer make sense, > and READ_POINTER for symmetry? What we do in some code is to comment the pairings, allowing the other side of the pairing to be easily located. Would that work for you? Thanx, Paul

...lease() to be paired with > the new improved READ_ONCE()? > > Thanx, Paul READ_ONCE is really all over the place (some code literally replaced all memory accesses with READ/WRITE ONCE). And I also prefer smp_wmb as it seems to be cheaper on ARM. Would an API like WRITE_POINTER()/smp_store_pointer make sense, and READ_POINTER for symmetry? -- MST

...mproved READ_ONCE()? > > > > READ_ONCE is really all over the place (some code literally replaced all > > memory accesses with READ/WRITE ONCE). > > > > And I also prefer smp_wmb as it seems to be cheaper on ARM. > > > > Would an API like WRITE_POINTER()/smp_store_pointer make sense, > > and READ_POINTER for symmetry? > > What we do in some code is to comment the pairings, allowing the other > side of the pairing to be easily located. Would that work for you? > > Thanx, Paul Yes, that's exactly what I did for now. Thanks! -- MS...

...cument the pairing *this read once has a barrier that is paired with that barrier*. > Complain to the compiler people for forcing us into that. In some cases when you end up with all accesses going through read/write once volatile just might better. > > Would an API like WRITE_POINTER()/smp_store_pointer make sense, > > and READ_POINTER for symmetry? > > No, the whole point of the exercise was to get away from the fact that > dependent loads are special. It's a pity that dependent stores are still special. -- MST