Messages in this thread Patch in this message | | | Date | Tue, 24 Jan 2006 15:46:13 +0100 | From | Eric Dumazet <> | Subject | [PATCH] [SMP] reduce size of percpudata, and make sure per_cpu(object, not_possible_cpu) cause an invalid memory reference |
| |
percpu_data blindly allocates bootmem memory to store NR_CPUS instances of cpudata, instead of allocating memory only for possible cpus.
This patch saves ram, allocating num_possible_cpus() (instead of NR_CPUS) instances.
This patch also makes sure a reference to per_cpu(object, not_possible_cpu) does a reference to invalid memory (NULL+small_offset).
As some architectures (x86_64) are now allocating cpudata only on possible cpus, we (kernel developers on x86 machines) should make sure that x86 does a similar thing to find bugs. This is important that this patch has some exposure in -mm for some time, some places must now use :
for_each_cpu(i) { ... per_cpu(xxx,i) ...
instead of the traditional
for (i = 0 ; i < NR_CPUS ; i++)
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> --- linux-2.6.16-rc1-mm2/init/main.c 2006-01-24 15:45:28.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/init/main.c 2006-01-24 16:31:53.000000000 +0100 @@ -334,6 +334,7 @@ { unsigned long size, i; char *ptr; + unsigned long nr_possible_cpus = num_possible_cpus(); /* Copy section for each CPU (we discard the original) */ size = ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES); @@ -341,12 +342,16 @@ if (size < PERCPU_ENOUGH_ROOM) size = PERCPU_ENOUGH_ROOM; #endif + ptr = alloc_bootmem(size * nr_possible_cpus); - ptr = alloc_bootmem(size * NR_CPUS); - - for (i = 0; i < NR_CPUS; i++, ptr += size) { + for (i = 0; i < NR_CPUS; i++) { + if (!cpu_possible(i)) { + __per_cpu_offset[i] = (char*)0 - __per_cpu_start; + continue; + } __per_cpu_offset[i] = ptr - __per_cpu_start; memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start); + ptr += size; } } #endif /* !__GENERIC_PER_CPU */ --- linux-2.6.16-rc1-mm2/block/ll_rw_blk.c 2006-01-24 15:57:29.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/block/ll_rw_blk.c 2006-01-24 15:57:40.000000000 +0100 @@ -3536,7 +3536,7 @@ iocontext_cachep = kmem_cache_create("blkdev_ioc", sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL); - for (i = 0; i < NR_CPUS; i++) + for_each_cpu(i) INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL); --- linux-2.6.16-rc1-mm2/drivers/scsi/scsi.c 2006-01-24 16:04:28.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/drivers/scsi/scsi.c 2006-01-24 16:04:40.000000000 +0100 @@ -1245,7 +1245,7 @@ if (error) goto cleanup_sysctl; - for (i = 0; i < NR_CPUS; i++) + for_each_cpu(i) INIT_LIST_HEAD(&per_cpu(scsi_done_q, i)); devfs_mk_dir("scsi"); --- linux-2.6.16-rc1-mm2/net/core/utils.c 2006-01-24 16:14:40.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/net/core/utils.c 2006-01-24 16:16:37.000000000 +0100 @@ -121,7 +121,7 @@ { int i; - for (i = 0; i < NR_CPUS; i++) { + for_each_cpu(i) { struct nrnd_state *state = &per_cpu(net_rand_state,i); __net_srandom(state, i+jiffies); } @@ -133,7 +133,7 @@ unsigned long seed[NR_CPUS]; get_random_bytes(seed, sizeof(seed)); - for (i = 0; i < NR_CPUS; i++) { + for_each_cpu(i) { struct nrnd_state *state = &per_cpu(net_rand_state,i); __net_srandom(state, seed[i]); } --- linux-2.6.16-rc1-mm2/net/core/dev.c 2006-01-24 16:24:24.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/net/core/dev.c 2006-01-24 16:24:46.000000000 +0100 @@ -3240,7 +3240,7 @@ * Initialise the packet receive queues. */ - for (i = 0; i < NR_CPUS; i++) { + for_each_cpu(i) { struct softnet_data *queue; queue = &per_cpu(softnet_data, i); --- linux-2.6.16-rc1-mm2/net/ipv4/proc.c 2006-01-24 16:18:13.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/net/ipv4/proc.c 2006-01-24 16:19:10.000000000 +0100 @@ -49,7 +49,7 @@ int res = 0; int cpu; - for (cpu = 0; cpu < NR_CPUS; cpu++) + for_each_cpu(cpu) res += proto->stats[cpu].inuse; return res; --- linux-2.6.16-rc1-mm2/net/ipv6/proc.c 2006-01-24 16:18:40.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/net/ipv6/proc.c 2006-01-24 16:19:10.000000000 +0100 @@ -38,7 +38,7 @@ int res = 0; int cpu; - for (cpu=0; cpu<NR_CPUS; cpu++) + for_each_cpu(cpu) res += proto->stats[cpu].inuse; return res; --- linux-2.6.16-rc1-mm2/net/socket.c 2006-01-24 16:19:01.000000000 +0100 +++ linux-2.6.16-rc1-mm2-ed/net/socket.c 2006-01-24 16:19:10.000000000 +0100 @@ -2079,7 +2079,7 @@ int cpu; int counter = 0; - for (cpu = 0; cpu < NR_CPUS; cpu++) + for_each_cpu(cpu) counter += per_cpu(sockets_in_use, cpu); /* It can be negative, by the way. 8) */ | |