2 commits

Author	SHA1	Message	Date
Paolo Bonzini	7b52aa7987	membarrier: add --enable-membarrier ... Actually enable the global memory barriers if supported by the OS. Because only recent versions of Linux include the support, they are disabled by default. Note that it also has to be disabled for QEMU to run under Wine. Before this patch, rcutorture reports 85 ns/read for my machine, after the patch it reports 12.5 ns/read. On the other hand updates go from 50 *micro*seconds to 20 *milli*seconds. Backports commit a40161cbe9ccbcbab798c3e4d257c4bba99d153a from qemu	2018-03-17 19:30:43 -04:00
Paolo Bonzini	67cb6d16ff	membarrier: introduce qemu/sys_membarrier.h ... This new header file provides heavy-weight "global" memory barriers that enforce memory ordering on each running thread belonging to the current process. For now, use a dummy implementation that issues memory barriers on both sides (matching what QEMU has been doing so far). Backports commit c8d3877e48c4f57381d72eaf8d016bff12ce2d7c from qemu	2018-03-17 19:19:28 -04:00