Basically, there was a pretty subtle race between the cpus in main where if the main cpu released the AP cpus and then before the AP cpus had a chance to run the boot cpu started creating the main thread (which causes smp ici messages to be created) the system would livelock, where the boot cpu waited forever for the AP cpu to acknowledge the ICI (for a TLB flush when creating the kernel stack).
Added smp_cpu_rendezvous(), used to synchronize all the cpus to a particular point, and used it a few times in main().
While i was at it i fixed another race that'll probably never happen, but what the hey. Make sure the kernel args are copied into kernel space by the main cpu before letting any other ones use it.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20269 a95241bf-73f2-0310-859d-f6bbb57e9c96
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