On Tue, May 09 2023 at 12:19, Peter Zijlstra wrote: > Again, not really this patch, but since I had to look at this code .... > > On Mon, May 08, 2023 at 09:43:39PM +0200, Thomas Gleixner wrote: >> @@ -1048,60 +1066,89 @@ static int do_boot_cpu(int apicid, int c > > /* > * AP might wait on cpu_callout_mask in cpu_init() with > * cpu_initialized_mask set if previous attempt to online > * it timed-out. Clear cpu_initialized_mask so that after > * INIT/SIPI it could start with a clean state. > */ > cpumask_clear_cpu(cpu, cpu_initialized_mask); > smp_mb(); > > ^^^ that barrier is weird too, cpumask_clear_cpu() is an atomic op and > implies much the same (this is x86 after all). If you want to be super > explicit about it write: > > smp_mb__after_atomic(); > > (which is a no-op) but then it still very much requires a comment as to > what exactly it orders against what. Won't bother either as that mask is gone a few patches later.
