[PATCH] __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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/init/main.c b/init/main.c
index 9cf6b30..2714e0e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -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;