Messages in this thread | | | Date | Wed, 1 Nov 2017 17:56:45 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 2/3 v4] x86/topology: Avoid wasting 128k for package id array |
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On Wed, 25 Oct 2017, Prarit Bhargava wrote: > diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h > index b390ff76e58f..f4ab1edf4e24 100644 > --- a/arch/x86/include/asm/processor.h > +++ b/arch/x86/include/asm/processor.h > @@ -124,8 +124,10 @@ struct cpuinfo_x86 { > u16 booted_cores; > /* Physical processor id: */ > u16 phys_proc_id; > - /* Logical processor id: */ > + /* Logical processor (package) id: */ > u16 logical_proc_id; > + /* Physical package ID */ > + u16 phys_pkg_id;
How is this new field used aside of being written to and how is it different from phys_proc_id? AFAICT, it's the same as all callers to topology_update_package_map() are handing in cpu_data->phys_proc_id.
> +/** > + * topology_phys_to_logical_pkg - Map a physical package id to a logical > + * > + * Returns logical package id or -1 if not found > + */ > +int topology_phys_to_logical_pkg(unsigned int phys_pkg) > +{ > + int log_pkg; > + > + for (log_pkg = 0; log_pkg < logical_packages; log_pkg++) > + if (logical_to_physical_pkg_map[log_pkg] == phys_pkg) > + return log_pkg; > + > + return -1; > +} > +EXPORT_SYMBOL(topology_phys_to_logical_pkg);
....
> + > + /* Allocate and copy a new array */ > + ltp_pkg_map_new = kmalloc(logical_packages * sizeof(u16), GFP_KERNEL); > + BUG_ON(!ltp_pkg_map_new); > + if (logical_to_physical_pkg_map) { > + memcpy(ltp_pkg_map_new, logical_to_physical_pkg_map, > + logical_packages * sizeof(u16)); > + kfree(logical_to_physical_pkg_map); > } > - physical_to_logical_pkg[pkg] = new; > + logical_to_physical_pkg_map = ltp_pkg_map_new;
This lacks serialization and is therefore broken against a concurrent topology_phys_to_logical_pkg() call for obvious reasons. The current user is probably safe, but this really needs to be fixed now.
Thanks,
tglx
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