missing error check in lwkt_alloc_thread

[Simon 'corecode' Schubert]

hey,

I just ran (via a programming mistake on my side) into a mall bug in lwkt_alloc_thread:

   if (stack == NULL) {
#ifdef _KERNEL
       stack = (void *)kmem_alloc(&kernel_map, stksize);
#else
       stack = libcaps_alloc_stack(stksize);
#endif
       flags |= TDF_ALLOCATED_STACK;
   }
kmem_alloc() however can return NULL if there is no free memory.  Arguably, if there is no free memory to satisfy a thread stack, you're hosed anyways, but nevertheless.

I'm not sure how to fix this.  Maybe something like this will be sufficient?

while (stack == NULL) {
 stack = (void *)kmem_alloc(&kernel_map, stksize);
 if (stack == NULL)
   tsleep(&kernel_map, 0, "stckalc", hz);
}
I know that there is nobody waking us up in this case, but one second should help the situation.  Or we add the possibility of an error return to lwkt_alloc_thread().

comments?

cheers
 simon
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