Messages in this thread | | | Date | Mon, 13 Mar 2006 10:39:32 -0800 | From | "Paul E. McKenney" <> | Subject | Re: Semantics of smp_mb() [was : Re: [PATCH] Fix RCU race in access of nohz_cpu_mask ] |
| |
On Thu, Dec 15, 2005 at 11:46:26PM -0800, Jeremy Higdon wrote: > Roland Dreier got this right. The purpose of the mmiowb is > to ensure that writes to I/O devices while holding a spinlock > are ordered with respect to writes issued after the original > processor releases and a second processor acquires said > spinlock. > > A MMIO read would be sufficient, but is much heavier weight. > > On the SGI MIPS-based systems, the "sync" instruction was used. > On the Altix systems, a register on the hub chip is read. > > >From comments by jejb, we're looking at modifying the mmiowb > API by adding an argument which would be a register to read > from if the architecture in question needs ordering in this > way but does not have a lighter weight mechanism like the Altix > mmiowb. Since there will now need to be a width indication, > mmiowb will be replaced with mmiowb[bwlq].
Any progress on this front? I figured that I would wait to update the ordering document until after this change happened, but if it is going to be awhile, I should proceed with the current API.
Thoughts?
Thanx, Paul - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |