In message <20020130214935.A7479@are.twiddle.net> you write:
> On Thu, Jan 31, 2002 at 09:45:45AM +1100, Rusty Russell wrote:
> > "better". Believe me, I was fully aware, but I refuse to write such
> > crap unless *proven* to be required.
>
> You're going to wait until the compiler generates incorrect
> code for you after knowing that it *probably* will? Nice.
It's a judgement call: the obvious code "might" fail, the obfuscated
code "might" fail. However, your judgment >> mine.
> "Small" variables may be positioned by the compiler such that
> they are addressable via a 16-bit relocation from some GP register.
> If that variable isn't actually located in the small data area,
> then the 16-bit relocation may overflow, resulting in link errors.
Ahhh... Thanks for the clue injection.
This better?
Rusty.
-- Anyone who quotes me in their sig is an idiot. -- Rusty Russell.diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/arch/i386/vmlinux.lds working-2.5.3-percpu/arch/i386/vmlinux.lds --- linux-2.5.3/arch/i386/vmlinux.lds Thu Jan 31 08:58:52 2002 +++ working-2.5.3-percpu/arch/i386/vmlinux.lds Fri Feb 1 09:11:18 2002 @@ -58,6 +58,10 @@ *(.initcall7.init) } __initcall_end = .; + . = ALIGN(32); + __per_cpu_start = .; + .data.percpu : { *(.data.percpu) } + __per_cpu_end = .; . = ALIGN(4096); __init_end = .; diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/arch/ppc/vmlinux.lds working-2.5.3-percpu/arch/ppc/vmlinux.lds --- linux-2.5.3/arch/ppc/vmlinux.lds Thu Jan 31 08:58:55 2002 +++ working-2.5.3-percpu/arch/ppc/vmlinux.lds Fri Feb 1 09:11:18 2002 @@ -104,6 +104,10 @@ *(.initcall7.init) } __initcall_end = .; + . = ALIGN(32); + __per_cpu_start = .; + .data.percpu : { *(.data.percpu) } + __per_cpu_end = .; . = ALIGN(4096); __init_end = .; diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/include/linux/cache.h working-2.5.3-percpu/include/linux/cache.h --- linux-2.5.3/include/linux/cache.h Fri Feb 1 19:21:37 2002 +++ working-2.5.3-percpu/include/linux/cache.h Fri Feb 1 19:17:09 2002 @@ -4,8 +4,10 @@ #include <linux/config.h> #include <asm/cache.h> +#define ALIGN(x,a) (((x)+(a)-1)&~((a)-1)) + #ifndef L1_CACHE_ALIGN -#define L1_CACHE_ALIGN(x) (((x)+(L1_CACHE_BYTES-1))&~(L1_CACHE_BYTES-1)) +#define L1_CACHE_ALIGN(x) ALIGN(x, L1_CACHE_BYTES) #endif #ifndef SMP_CACHE_BYTES diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/include/linux/compiler.h working-2.5.3-percpu/include/linux/compiler.h --- linux-2.5.3/include/linux/compiler.h Wed Sep 19 07:12:45 2001 +++ working-2.5.3-percpu/include/linux/compiler.h Fri Feb 1 09:46:02 2002 @@ -13,4 +13,12 @@ #define likely(x) __builtin_expect((x),1) #define unlikely(x) __builtin_expect((x),0) +/* This macro obfuscates arithmetic on a variable address so that gcc + shouldn't recognize it. This prevents optimizations such as the + famous: + strcpy(s, "xxx"+X) => memcpy(s, "xxx"+X, 4-X) */ +#define rth(var, off) \ + ({ __typeof__(&(var)) __ptr; \ + __asm__ ("" : "=g"(__ptr) : "0"((void *)&(var) + (off))); \ + *__ptr; }) #endif /* __LINUX_COMPILER_H */ diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/include/linux/interrupt.h working-2.5.3-percpu/include/linux/interrupt.h --- linux-2.5.3/include/linux/interrupt.h Fri Feb 1 19:21:37 2002 +++ working-2.5.3-percpu/include/linux/interrupt.h Fri Feb 1 19:27:57 2002 @@ -124,14 +124,6 @@ TASKLET_STATE_RUN /* Tasklet is running (SMP only) */ }; -struct tasklet_head -{ - struct tasklet_struct *list; -} __attribute__ ((__aligned__(SMP_CACHE_BYTES))); - -extern struct tasklet_head tasklet_vec[NR_CPUS]; -extern struct tasklet_head tasklet_hi_vec[NR_CPUS]; - #ifdef CONFIG_SMP static inline int tasklet_trylock(struct tasklet_struct *t) { diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/include/linux/smp.h working-2.5.3-percpu/include/linux/smp.h --- linux-2.5.3/include/linux/smp.h Fri Feb 1 19:21:37 2002 +++ working-2.5.3-percpu/include/linux/smp.h Fri Feb 1 19:17:09 2002 @@ -11,6 +11,7 @@ #ifdef CONFIG_SMP #include <linux/kernel.h> +#include <linux/compiler.h> #include <asm/smp.h> /* @@ -71,7 +72,17 @@ #define MSG_RESCHEDULE 0x0003 /* Reschedule request from master CPU*/ #define MSG_CALL_FUNCTION 0x0004 /* Call function on all other CPUs */ -#else +#define __per_cpu_data __attribute__((section(".data.percpu"))) + +#ifndef __HAVE_ARCH_PER_CPU +extern unsigned long __per_cpu_offset[NR_CPUS]; + +/* var is in discarded region: offset to particular copy we want */ +#define per_cpu(var, cpu) rth(var, per_cpu_offset(cpu)) + +#define this_cpu(var) per_cpu(var, smp_processor_id()) +#endif /* !__HAVE_ARCH_PER_CPU */ +#else /* !SMP */ /* * These macros fold the SMP functionality into a single CPU system @@ -88,6 +99,9 @@ #define cpu_online_map 1 static inline void smp_send_reschedule(int cpu) { } static inline void smp_send_reschedule_all(void) { } +#define __per_cpu_data +#define per_cpu(var, cpu) var +#define this_cpu(var) var #endif #endif diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/init/main.c working-2.5.3-percpu/init/main.c --- linux-2.5.3/init/main.c Thu Jan 31 08:59:17 2002 +++ working-2.5.3-percpu/init/main.c Fri Feb 1 19:13:52 2002 @@ -272,8 +272,32 @@ #define smp_init() do { } while (0) #endif +static inline void setup_per_cpu_areas(void) +{ +} #else +#ifndef __HAVE_ARCH_PER_CPU +unsigned long __per_cpu_offset[NR_CPUS]; + +static void __init setup_per_cpu_areas(void) +{ + unsigned long size, i; + char *ptr; + /* Created by linker magic */ + extern char __per_cpu_start[], __per_cpu_end[]; + + /* Copy section for each CPU (we discard the original) */ + size = ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES); + ptr = alloc_bootmem(size * NR_CPUS); + + for (i = 0; i < NR_CPUS; i++, ptr += size) { + __per_cpu_offset[i] = ptr - __per_cpu_start; + memcpy(ptr, __per_cpu_start, size); + } +} +#endif /* !__HAVE_ARCH_PER_CPU */ + /* Called by boot processor to activate the rest. */ static void __init smp_init(void) { @@ -316,6 +340,7 @@ lock_kernel(); printk(linux_banner); setup_arch(&command_line); + setup_per_cpu_areas(); printk("Kernel command line: %s\n", saved_command_line); parse_options(command_line); trap_init(); diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/kernel/ksyms.c working-2.5.3-percpu/kernel/ksyms.c --- linux-2.5.3/kernel/ksyms.c Thu Jan 31 08:59:17 2002 +++ working-2.5.3-percpu/kernel/ksyms.c Fri Feb 1 09:11:18 2002 @@ -543,8 +543,6 @@ EXPORT_SYMBOL(strsep); /* software interrupts */ -EXPORT_SYMBOL(tasklet_hi_vec); -EXPORT_SYMBOL(tasklet_vec); EXPORT_SYMBOL(bh_task_vec); EXPORT_SYMBOL(init_bh); EXPORT_SYMBOL(remove_bh); diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.3/kernel/softirq.c working-2.5.3-percpu/kernel/softirq.c --- linux-2.5.3/kernel/softirq.c Thu Jan 31 08:59:17 2002 +++ working-2.5.3-percpu/kernel/softirq.c Fri Feb 1 09:11:18 2002 @@ -145,9 +145,13 @@ /* Tasklets */ +struct tasklet_head +{ + struct tasklet_struct *list; +}; -struct tasklet_head tasklet_vec[NR_CPUS] __cacheline_aligned_in_smp; -struct tasklet_head tasklet_hi_vec[NR_CPUS] __cacheline_aligned_in_smp; +static struct tasklet_head tasklet_vec __per_cpu_data; +static struct tasklet_head tasklet_hi_vec __per_cpu_data; void __tasklet_schedule(struct tasklet_struct *t) { @@ -155,8 +159,8 @@ unsigned long flags; local_irq_save(flags); - t->next = tasklet_vec[cpu].list; - tasklet_vec[cpu].list = t; + t->next = per_cpu(tasklet_vec, cpu).list; + per_cpu(tasklet_vec, cpu).list = t; cpu_raise_softirq(cpu, TASKLET_SOFTIRQ); local_irq_restore(flags); } @@ -167,8 +171,8 @@ unsigned long flags; local_irq_save(flags); - t->next = tasklet_hi_vec[cpu].list; - tasklet_hi_vec[cpu].list = t; + t->next = per_cpu(tasklet_hi_vec, cpu).list; + per_cpu(tasklet_hi_vec, cpu).list = t; cpu_raise_softirq(cpu, HI_SOFTIRQ); local_irq_restore(flags); } @@ -179,8 +183,8 @@ struct tasklet_struct *list; local_irq_disable(); - list = tasklet_vec[cpu].list; - tasklet_vec[cpu].list = NULL; + list = per_cpu(tasklet_vec, cpu).list; + per_cpu(tasklet_vec, cpu).list = NULL; local_irq_enable(); while (list) { @@ -200,8 +204,8 @@ } local_irq_disable(); - t->next = tasklet_vec[cpu].list; - tasklet_vec[cpu].list = t; + t->next = per_cpu(tasklet_vec, cpu).list; + per_cpu(tasklet_vec, cpu).list = t; __cpu_raise_softirq(cpu, TASKLET_SOFTIRQ); local_irq_enable(); } @@ -213,8 +217,8 @@ struct tasklet_struct *list; local_irq_disable(); - list = tasklet_hi_vec[cpu].list; - tasklet_hi_vec[cpu].list = NULL; + list = per_cpu(tasklet_hi_vec, cpu).list; + per_cpu(tasklet_hi_vec, cpu).list = NULL; local_irq_enable(); while (list) { @@ -234,8 +238,8 @@ } local_irq_disable(); - t->next = tasklet_hi_vec[cpu].list; - tasklet_hi_vec[cpu].list = t; + t->next = per_cpu(tasklet_hi_vec, cpu).list; + per_cpu(tasklet_hi_vec, cpu).list = t; __cpu_raise_softirq(cpu, HI_SOFTIRQ); local_irq_enable(); } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Feb 07 2002 - 21:00:11 EST