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From: Rusty Russell <rusty@rustcorp.com.au>
To: linux-kernel@vger.kernel.org
Subject: [PATCH] 2.5.1-pre5: per-cpu areas
Date: Thu, 06 Dec 2001 09:09:35 +1100
Cc: torvalds@transmeta.com
The following patch implements convenient per-cpu areas:
DECLARE_PER_CPU(int myvar);
...
this_cpu(myvar) = 1;
for (i = 0; i < NR_CPUS; i++)
per_cpu(myvar, i) = 0;
Good: Simply referring to "myvar" won't work (even on Uniprocessor), so
that mistake is prevented. Unreferenced variables are warned like
normal (almost).
Bad: Initialization isn't possible in the declaration. Only
implemented for PPC and x86, but fix is trivial for other
architectures. Implementation is icky, but getting the linker to
duplicate per-cpu section itself without symbols is beyond my skill.
Feedback appreciated,
Rusty.
--
Anyone who quotes me is an idiot. -- Rusty Russell.
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.1-pre5/include/linux/smp.h working-2.5.1-pre5-percpu/include/linux/smp.h
--- linux-2.5.1-pre5/include/linux/smp.h Wed Dec 5 16:49:14 2001
+++ working-2.5.1-pre5-percpu/include/linux/smp.h Wed Dec 5 18:21:06 2001
@@ -71,7 +71,36 @@
#define MSG_RESCHEDULE 0x0003 /* Reschedule request from master CPU*/
#define MSG_CALL_FUNCTION 0x0004 /* Call function on all other CPUs */
+#define __PER_CPU(decl,num) decl##__##num \
+ __attribute__((section(".data.cpu" #num)))
+
+#if NR_CPUS == 32
+#define PER_CPU(decl) __PER_CPU(decl, 0); __PER_CPU(decl, 1); \
+ __PER_CPU(decl, 2); __PER_CPU(decl, 3); \
+ __PER_CPU(decl, 4); __PER_CPU(decl, 5); \
+ __PER_CPU(decl, 6); __PER_CPU(decl, 7); \
+ __PER_CPU(decl, 8); __PER_CPU(decl, 9); \
+ __PER_CPU(decl, 10); __PER_CPU(decl, 11); \
+ __PER_CPU(decl, 12); __PER_CPU(decl, 13); \
+ __PER_CPU(decl, 14); __PER_CPU(decl, 15); \
+ __PER_CPU(decl, 16); __PER_CPU(decl, 17); \
+ __PER_CPU(decl, 18); __PER_CPU(decl, 19); \
+ __PER_CPU(decl, 20); __PER_CPU(decl, 21); \
+ __PER_CPU(decl, 22); __PER_CPU(decl, 23); \
+ __PER_CPU(decl, 24); __PER_CPU(decl, 25); \
+ __PER_CPU(decl, 26); __PER_CPU(decl, 27); \
+ __PER_CPU(decl, 28); __PER_CPU(decl, 29); \
+ __PER_CPU(decl, 30); __PER_CPU(decl, 31)
#else
+#error NR_CPUS not 32: fix linux/smp.h.
+#endif /* NR_CPUS */
+
+extern void *per_cpu_sections[NR_CPUS];
+
+#define per_cpu(var, cpu) \
+*(__typeof__(&var)(&var##__0 - per_cpu_sections[0]) + per_cpu_sections[cpu])
+
+#else /* !SMP */
/*
* These macros fold the SMP functionality into a single CPU system
@@ -86,6 +115,10 @@
#define cpu_number_map(cpu) 0
#define smp_call_function(func,info,retry,wait) ({ 0; })
#define cpu_online_map 1
-
+#define PER_CPU(decl) decl
+#define per_cpu(var, cpu) var
#endif
+
+#define this_cpu(var) per_cpu(var,smp_processor_id())
+
#endif
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.1-pre5/init/main.c working-2.5.1-pre5-percpu/init/main.c
--- linux-2.5.1-pre5/init/main.c Tue Dec 4 17:17:28 2001
+++ working-2.5.1-pre5-percpu/init/main.c Wed Dec 5 17:41:56 2001
@@ -499,6 +499,19 @@
#else
+#if NR_CPUS != 32
+#error NR_CPUS not 32: fix init/main.c.
+#endif
+/* Created by linker magic */
+extern void *__cpu0, *__cpu1, *__cpu2, *__cpu3,
+ *__cpu4, *__cpu5, *__cpu6, *__cpu7,
+ *__cpu8, *__cpu9, *__cpu10, *__cpu11,
+ *__cpu12, *__cpu13, *__cpu14, *__cpu15,
+ *__cpu16, *__cpu17, *__cpu18, *__cpu19,
+ *__cpu20, *__cpu21, *__cpu22, *__cpu23,
+ *__cpu24, *__cpu25, *__cpu26, *__cpu27,
+ *__cpu28, *__cpu29, *__cpu30, *__cpu31;
+void *per_cpu_sections[NR_CPUS];
/* Called by boot processor to activate the rest. */
static void __init smp_init(void)
@@ -518,6 +531,24 @@
barrier();
}
printk("All processors have done init_idle\n");
+
+ /* Set up per-CPU section pointers */
+ per_cpu_sections[0] = &__cpu0; per_cpu_sections[1] = &__cpu1;
+ per_cpu_sections[2] = &__cpu2; per_cpu_sections[3] = &__cpu3;
+ per_cpu_sections[4] = &__cpu4; per_cpu_sections[5] = &__cpu5;
+ per_cpu_sections[6] = &__cpu6; per_cpu_sections[7] = &__cpu7;
+ per_cpu_sections[8] = &__cpu8; per_cpu_sections[9] = &__cpu9;
+ per_cpu_sections[10] = &__cpu10; per_cpu_sections[11] = &__cpu11;
+ per_cpu_sections[12] = &__cpu12; per_cpu_sections[13] = &__cpu13;
+ per_cpu_sections[14] = &__cpu14; per_cpu_sections[15] = &__cpu15;
+ per_cpu_sections[16] = &__cpu16; per_cpu_sections[17] = &__cpu17;
+ per_cpu_sections[18] = &__cpu18; per_cpu_sections[19] = &__cpu19;
+ per_cpu_sections[20] = &__cpu20; per_cpu_sections[21] = &__cpu21;
+ per_cpu_sections[22] = &__cpu22; per_cpu_sections[23] = &__cpu23;
+ per_cpu_sections[24] = &__cpu24; per_cpu_sections[25] = &__cpu25;
+ per_cpu_sections[26] = &__cpu26; per_cpu_sections[27] = &__cpu27;
+ per_cpu_sections[28] = &__cpu28; per_cpu_sections[29] = &__cpu29;
+ per_cpu_sections[30] = &__cpu30; per_cpu_sections[31] = &__cpu31;
}
#endif
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.1-pre5/arch/i386/vmlinux.lds working-2.5.1-pre5-percpu/arch/i386/vmlinux.lds
--- linux-2.5.1-pre5/arch/i386/vmlinux.lds Tue Jul 3 07:40:14 2001
+++ working-2.5.1-pre5-percpu/arch/i386/vmlinux.lds Wed Dec 5 18:03:50 2001
@@ -34,6 +34,40 @@
CONSTRUCTORS
}
+ /* Per-cpu sections: cache-line aligned */
+ . = ALIGN(32); __cpu0 = .; .data.cpu0 : { *(.data.cpu0) }
+ . = ALIGN(32); __cpu1 = .; .data.cpu1 : { *(.data.cpu1) }
+ . = ALIGN(32); __cpu2 = .; .data.cpu2 : { *(.data.cpu2) }
+ . = ALIGN(32); __cpu3 = .; .data.cpu3 : { *(.data.cpu3) }
+ . = ALIGN(32); __cpu4 = .; .data.cpu4 : { *(.data.cpu4) }
+ . = ALIGN(32); __cpu5 = .; .data.cpu5 : { *(.data.cpu5) }
+ . = ALIGN(32); __cpu6 = .; .data.cpu6 : { *(.data.cpu6) }
+ . = ALIGN(32); __cpu7 = .; .data.cpu7 : { *(.data.cpu7) }
+ . = ALIGN(32); __cpu8 = .; .data.cpu8 : { *(.data.cpu8) }
+ . = ALIGN(32); __cpu9 = .; .data.cpu9 : { *(.data.cpu9) }
+ . = ALIGN(32); __cpu10 = .; .data.cpu10 : { *(.data.cpu10) }
+ . = ALIGN(32); __cpu11 = .; .data.cpu11 : { *(.data.cpu11) }
+ . = ALIGN(32); __cpu12 = .; .data.cpu12 : { *(.data.cpu12) }
+ . = ALIGN(32); __cpu13 = .; .data.cpu13 : { *(.data.cpu13) }
+ . = ALIGN(32); __cpu14 = .; .data.cpu14 : { *(.data.cpu14) }
+ . = ALIGN(32); __cpu15 = .; .data.cpu15 : { *(.data.cpu15) }
+ . = ALIGN(32); __cpu16 = .; .data.cpu16 : { *(.data.cpu16) }
+ . = ALIGN(32); __cpu17 = .; .data.cpu17 : { *(.data.cpu17) }
+ . = ALIGN(32); __cpu18 = .; .data.cpu18 : { *(.data.cpu18) }
+ . = ALIGN(32); __cpu19 = .; .data.cpu19 : { *(.data.cpu19) }
+ . = ALIGN(32); __cpu20 = .; .data.cpu20 : { *(.data.cpu20) }
+ . = ALIGN(32); __cpu21 = .; .data.cpu21 : { *(.data.cpu21) }
+ . = ALIGN(32); __cpu22 = .; .data.cpu22 : { *(.data.cpu22) }
+ . = ALIGN(32); __cpu23 = .; .data.cpu23 : { *(.data.cpu23) }
+ . = ALIGN(32); __cpu24 = .; .data.cpu24 : { *(.data.cpu24) }
+ . = ALIGN(32); __cpu25 = .; .data.cpu25 : { *(.data.cpu25) }
+ . = ALIGN(32); __cpu26 = .; .data.cpu26 : { *(.data.cpu26) }
+ . = ALIGN(32); __cpu27 = .; .data.cpu27 : { *(.data.cpu27) }
+ . = ALIGN(32); __cpu28 = .; .data.cpu28 : { *(.data.cpu28) }
+ . = ALIGN(32); __cpu29 = .; .data.cpu29 : { *(.data.cpu29) }
+ . = ALIGN(32); __cpu30 = .; .data.cpu30 : { *(.data.cpu30) }
+ . = ALIGN(32); __cpu31 = .; .data.cpu31 : { *(.data.cpu31) }
+
_edata = .; /* End of data section */
. = ALIGN(8192); /* init_task */
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.1-pre5/arch/ppc/vmlinux.lds working-2.5.1-pre5-percpu/arch/ppc/vmlinux.lds
--- linux-2.5.1-pre5/arch/ppc/vmlinux.lds Tue Aug 28 23:58:33 2001
+++ working-2.5.1-pre5-percpu/arch/ppc/vmlinux.lds Wed Dec 5 18:03:57 2001
@@ -58,6 +58,41 @@
*(.dynamic)
CONSTRUCTORS
}
+
+ /* Per-cpu sections: cache-line aligned */
+ . = ALIGN(32); __cpu0 = .; .data.cpu0 : { *(.data.cpu0) }
+ . = ALIGN(32); __cpu1 = .; .data.cpu1 : { *(.data.cpu1) }
+ . = ALIGN(32); __cpu2 = .; .data.cpu2 : { *(.data.cpu2) }
+ . = ALIGN(32); __cpu3 = .; .data.cpu3 : { *(.data.cpu3) }
+ . = ALIGN(32); __cpu4 = .; .data.cpu4 : { *(.data.cpu4) }
+ . = ALIGN(32); __cpu5 = .; .data.cpu5 : { *(.data.cpu5) }
+ . = ALIGN(32); __cpu6 = .; .data.cpu6 : { *(.data.cpu6) }
+ . = ALIGN(32); __cpu7 = .; .data.cpu7 : { *(.data.cpu7) }
+ . = ALIGN(32); __cpu8 = .; .data.cpu8 : { *(.data.cpu8) }
+ . = ALIGN(32); __cpu9 = .; .data.cpu9 : { *(.data.cpu9) }
+ . = ALIGN(32); __cpu10 = .; .data.cpu10 : { *(.data.cpu10) }
+ . = ALIGN(32); __cpu11 = .; .data.cpu11 : { *(.data.cpu11) }
+ . = ALIGN(32); __cpu12 = .; .data.cpu12 : { *(.data.cpu12) }
+ . = ALIGN(32); __cpu13 = .; .data.cpu13 : { *(.data.cpu13) }
+ . = ALIGN(32); __cpu14 = .; .data.cpu14 : { *(.data.cpu14) }
+ . = ALIGN(32); __cpu15 = .; .data.cpu15 : { *(.data.cpu15) }
+ . = ALIGN(32); __cpu16 = .; .data.cpu16 : { *(.data.cpu16) }
+ . = ALIGN(32); __cpu17 = .; .data.cpu17 : { *(.data.cpu17) }
+ . = ALIGN(32); __cpu18 = .; .data.cpu18 : { *(.data.cpu18) }
+ . = ALIGN(32); __cpu19 = .; .data.cpu19 : { *(.data.cpu19) }
+ . = ALIGN(32); __cpu20 = .; .data.cpu20 : { *(.data.cpu20) }
+ . = ALIGN(32); __cpu21 = .; .data.cpu21 : { *(.data.cpu21) }
+ . = ALIGN(32); __cpu22 = .; .data.cpu22 : { *(.data.cpu22) }
+ . = ALIGN(32); __cpu23 = .; .data.cpu23 : { *(.data.cpu23) }
+ . = ALIGN(32); __cpu24 = .; .data.cpu24 : { *(.data.cpu24) }
+ . = ALIGN(32); __cpu25 = .; .data.cpu25 : { *(.data.cpu25) }
+ . = ALIGN(32); __cpu26 = .; .data.cpu26 : { *(.data.cpu26) }
+ . = ALIGN(32); __cpu27 = .; .data.cpu27 : { *(.data.cpu27) }
+ . = ALIGN(32); __cpu28 = .; .data.cpu28 : { *(.data.cpu28) }
+ . = ALIGN(32); __cpu29 = .; .data.cpu29 : { *(.data.cpu29) }
+ . = ALIGN(32); __cpu30 = .; .data.cpu30 : { *(.data.cpu30) }
+ . = ALIGN(32); __cpu31 = .; .data.cpu31 : { *(.data.cpu31) }
+
_edata = .;
PROVIDE (edata = .);
-
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