* Vivek Goyal <vgoyal at in.ibm.com> [2007-10-17 13:05]: > > [..] > > +/* > > + * If flags is 0, then the return value is always 0 (success). If > > + * flags contains BOOTMEM_EXCLUSIVE, then -EBUSY is returned if the > > + * memory already was reserved. > > + */ > > +extern int reserve_bootmem(unsigned long addr, unsigned long size, int flags); > > #define alloc_bootmem(x) \ > > __alloc_bootmem(x, SMP_CACHE_BYTES, __pa(MAX_DMA_ADDRESS)) > > #define alloc_bootmem_low(x) \ > > --- a/mm/bootmem.c > > +++ b/mm/bootmem.c > > @@ -111,8 +111,8 @@ static unsigned long __init init_bootmem > > * might be used for boot-time allocations - or it might get added > > * to the free page pool later on. > > */ > > -static void __init reserve_bootmem_core(bootmem_data_t *bdata, unsigned long addr, > > - unsigned long size) > > +static int __init reserve_bootmem_core(bootmem_data_t *bdata, unsigned long addr, > > + unsigned long size, int flags) > > { > > unsigned long sidx, eidx; > > unsigned long i; > > @@ -133,7 +133,11 @@ static void __init reserve_bootmem_core( > > #ifdef CONFIG_DEBUG_BOOTMEM > > printk("hm, page %08lx reserved twice.\n", i*PAGE_SIZE); > > #endif > > + if (flags & BOOTMEM_EXCLUSIVE) > > + return -EBUSY; > > I think we should unreserve the chunks of memory we have reserved so > far (Memory reserved from sidx to i), in case of error. Unfortunately, that's not possible without using a lock (or counters instead of a bitmap) any more. If we just do for (i--; i >= sidx; i--) clear_bit(i, bdata->node_bootmem_map); then another thread of execution could reserve the memory (without BOOTMEM_EXCLUSIVE) in between -- and the code would free the memory which is already reserved. I think that could be modelled with a rwlock, not changing the default case where BOOTMEM_EXCLUSIVE is not specified. Thanks, Bernhard