Messages in this thread | | | Date | Sun, 19 Jan 2014 00:04:05 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock() |
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On Sat, Jan 18, 2014 at 04:57:05PM -0800, Linus Torvalds wrote: > On Sat, Jan 18, 2014 at 1:22 PM, Paul E. McKenney > <paulmck@linux.vnet.ibm.com> wrote: > > > > Yes, this requires that -all- updates to the fields in the machine word > > in question use atomic rmw. Which would not be pretty from a core-code > > perspective. Hence my suggestion of ceasing Linux-kernel support for > > DEC Alpha CPUs that don't support byte operations. Also need 16-bit > > operations as well, of course... > > I'm not seeing this. > > Why the hell would you have byte- or halfword-sized versions of the > store_release or load_acquire things on alpha anyway? > > What it means is that data structures that do locking or atomics need > to be "int" or "long" on alpha. That has always been true. What do > you claim has changed?
OK, another approach would be to never add "select ARCH_USE_QUEUE_RWLOCK" on Alpha, at least if the queued rwlocks really do want to atomically manipulate bytes. After all, the Alpha systems that I know about don't have enough CPUs to make queued rwlocks necessary anyway.
Much simpler solution!
Is this what you were getting at, or am I missing your point?
Thanx, Paul
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