On Mon, 13 Sep 2010 15:18:38 -0400 John Baldwin <j...@freebsd.org> wrote:
> On Monday, September 13, 2010 2:48:23 pm Matthew D Fleming wrote: > > Author: mdf > > Date: Mon Sep 13 18:48:23 2010 > > New Revision: 212572 > > URL: http://svn.freebsd.org/changeset/base/212572 > > > > Log: > > Revert r212370, as it causes a LOR on powerpc. powerpc does a few > > unexpected things in copyout(9) and so wiring the user buffer is > > not sufficient to perform a copyout(9) while holding a random mutex. > > > > Requested by: nwhitehorn > > Hmmm, that is going to break several other sysctls as well then. > Many sysctls use sysctl_wire_old_buffer() explicitly so that they can > then call SYSCTL_OUT() without dropping a lock. The pcblist sysctls > do this for example I think. In general code in the kernel assumes > that copyout(9) to/from a wired buffer is safe while holding mutexes > or rwlocks. > Yes. The issue here is that powerpc64 copyin/out() needs to acquire the PMAP lock, so holding normal mutexes is fine, but calling into copyout() with non-sleepable locks like this code did is not. Matthew and I are working on a better solution that fixes this on the powerpc copyout() side, but it is tricky for a variety of reasons and will take a little while. In the meantime, this keeps powerpc64 systems bootable. -Nathan _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
