Hi,
Does use of wmb() and rmb() for amd64 as defined in
sys/amd64/include/atomic.h required use of critical_enter()/critical_exit().
I was looking at the code in sys/amd64/amd64/cpu_switch.S which switches
between threads and I don't see any "sfence" instructions in there.
Given the following piece of dummy code:
var_a = 1;
var_b = 2;
wmb();
If there is a task switch between writing var_a and var_b so that the
thread in question continues executing on another core, can it happen
that the write to var_a is not flushed when wmb() is executed?
var_a = 1;
<task switch to different CPU core>
var_b = 2;
wmb();
--HPS
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