On 5 Oct, Konstantin Belousov wrote: > Author: kib > Date: Thu Oct 5 12:50:03 2017 > New Revision: 324313 > URL: https://svnweb.freebsd.org/changeset/base/324313 > > Log: > Avoid a race betweem freeing LDT and context switches. > > cpu_switch.S uses curproc->p_md.md_ldt value as the flag indicating > presence of the process LDT. The flag is checked and then ldt segment > descriptor is copied into the CPU' GDT slot. > > Disallow context switches around clearing of the curproc LDT state by > performing the cleanup in critical section. Ensure that the md_ldt > flag is cleared before md_ldt_sd descriptor content is destroyed by > inserting fence between the operations. > > We depend on the x86 memory model strong ordering guarantees, in > particular, that cpu_switch.S observes the writes to md_ldt and > md_ldt_sd in the expected order.
I don't know which of this series of commits is responsible, but I think that it fixed the build of lang/ghc on Ryzen. https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221029#c102 _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
