Messages in this thread Patch in this message | | | Date | Wed, 01 Feb 2006 10:21:10 +0100 | From | Eric Dumazet <> | Subject | [PATCH] [SMP] __GENERIC_PER_CPU changes |
| |
Now CONFIG_DEBUG_INITDATA is in, initial percpu data [__per_cpu_start,__per_cpu_end] can be declared as a redzone, and invalid accesses after boot can be detected, at least for i386.
We can let non possible cpus percpu data point to this 'redzone' instead of NULL .
NULL was not a good choice because part of [0..32768] memory may be readable and invalid accesses may happen unnoticed.
If CONFIG_DEBUG_INITDATA is not defined, each non possible cpu points to the initial percpu data (__per_cpu_offset[cpu] == 0), thus invalid accesses wont be detected/crash.
This patch also moves __per_cpu_offset[] to read_mostly area to avoid false sharing.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> --- a/init/main.c 2006-02-01 10:44:10.000000000 +0100 +++ b/init/main.c 2006-02-01 10:50:16.000000000 +0100 @@ -325,7 +325,7 @@ #else #ifdef __GENERIC_PER_CPU -unsigned long __per_cpu_offset[NR_CPUS]; +unsigned long __per_cpu_offset[NR_CPUS] __read_mostly; EXPORT_SYMBOL(__per_cpu_offset); @@ -343,11 +343,7 @@ #endif ptr = alloc_bootmem(size * nr_possible_cpus); - for (i = 0; i < NR_CPUS; i++) { - if (!cpu_possible(i)) { - __per_cpu_offset[i] = (char*)0 - __per_cpu_start; - continue; - } + for_each_cpu(i) { __per_cpu_offset[i] = ptr - __per_cpu_start; memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start); ptr += size; | |