Change in coreboot[master]: cpu/x86/mp_init.c: Add wait_finished_mp_run_on_all_cpus

[Kane Chen (Code Review)]

Attention is currently required from: Subrata Banik, Tim Wawrzynczak, Arthur Heymans.
Kane Chen has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63566 )

Change subject: cpu/x86/mp_init.c: Add wait_finished_mp_run_on_all_cpus
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Patch Set 2:

(1 comment)

File src/cpu/x86/mp_init.c:

https://review.coreboot.org/c/coreboot/+/63566/comment/2f8bb2b3_1dbc1a78 
PS2, Line 984: mp_run_on_aps_and_wait_for_complete
> isn't this is also similar to running AP processes in serialised manner ?

which function? did you mean mp_run_on_all_aps?
if so, it's kind of different.
original code call store_callback before lcb.func(lcb.arg) only
At this point, BSP thinks APs already take the job and continue running.
Even you serialise AP task, it still can't guarantee APs finish tasks.

with wait_ap_complete, APs call store_callback after lcb.func(lcb.arg);
so it ensures the tasks are really finished.