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SubjectRe: [PATCH v2 5/6] arch: simplify several early memory allocations
On Mon, Dec 03, 2018 at 05:29:08PM +0100, Sam Ravnborg wrote:
> Hi Mike.
>
> > index c37955d..2a17665 100644
> > --- a/arch/sparc/kernel/prom_64.c
> > +++ b/arch/sparc/kernel/prom_64.c
> > @@ -34,16 +34,13 @@
> >
> > void * __init prom_early_alloc(unsigned long size)
> > {
> > - unsigned long paddr = memblock_phys_alloc(size, SMP_CACHE_BYTES);
> > - void *ret;
> > + void *ret = memblock_alloc(size, SMP_CACHE_BYTES);
> >
> > - if (!paddr) {
> > + if (!ret) {
> > prom_printf("prom_early_alloc(%lu) failed\n", size);
> > prom_halt();
> > }
> >
> > - ret = __va(paddr);
> > - memset(ret, 0, size);
> > prom_early_allocated += size;
> >
> > return ret;
>
> memblock_alloc() calls memblock_alloc_try_nid().
> And if allocation fails then memblock_alloc_try_nid() calls panic().
> So will we ever hit the prom_halt() code?

memblock_phys_alloc_try_nid() also calls panic if an allocation fails. So
in either case we never reach prom_halt() code.

Actually, sparc is rather an exception from the general practice to rely on
panic() inside the early allocator rather than to check the return value.

> Do we have a panic() implementation that actually returns?
>
>
> > diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> > index 3c8aac2..52884f4 100644
> > --- a/arch/sparc/mm/init_64.c
> > +++ b/arch/sparc/mm/init_64.c
> > @@ -1089,16 +1089,13 @@ static void __init allocate_node_data(int nid)
> > struct pglist_data *p;
> > unsigned long start_pfn, end_pfn;
> > #ifdef CONFIG_NEED_MULTIPLE_NODES
> > - unsigned long paddr;
> >
> > - paddr = memblock_phys_alloc_try_nid(sizeof(struct pglist_data),
> > - SMP_CACHE_BYTES, nid);
> > - if (!paddr) {
> > + NODE_DATA(nid) = memblock_alloc_node(sizeof(struct pglist_data),
> > + SMP_CACHE_BYTES, nid);
> > + if (!NODE_DATA(nid)) {
> > prom_printf("Cannot allocate pglist_data for nid[%d]\n", nid);
> > prom_halt();
> > }
> > - NODE_DATA(nid) = __va(paddr);
> > - memset(NODE_DATA(nid), 0, sizeof(struct pglist_data));
> >
> > NODE_DATA(nid)->node_id = nid;
> > #endif
>
> Same here.
>
> I did not look at the other cases.

I really tried to be careful and did the replacements only for the calls
that do panic if an allocation fails.

> Sam
>

--
Sincerely yours,
Mike.

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