[PATCH] cpumask 5/10 rewrite cpumask.h - single bitmap based implementation

Paul Jackson
2004-06-03T17:26:59Z

cpumask 5/10 rewrite cpumask.h - single bitmap based implementation

Major rewrite of cpumask to use a single implementation,
as a struct-wrapped bitmap.

This patch leaves some 26 include/asm-*/cpumask*.h
header files orphaned - to be removed next patch.

Some nine cpumask macros for const variants and to
coerce and promote between an unsigned long and a
cpumask are obsolete. Simple emulation wrappers are
provided in this patch for these obsolete macros,
which can be removed once each of the 3 archs (i386,
ppc64, x86_64) using them are recoded in follow-on
patches to not need them.

The CPU_MASK_ALL macro now avoids leaving possible
garbage one bits in any unused portion of the high word.

An inproved comment lists all available operators, for
convenient browsing.

arch/sparc64/kernel/irq.c | 6
include/linux/cpumask.h | 409 +++++++++++++++++++++--
kernel/rcupdate.c | 7
kernel/sched.c | 5
4 files changed, 387 insertions(+), 40 deletions(-)

Signed-off-by: Paul Jackson <pj@sgi.com>

Index: 2.6.7-rc2-mm2/include/linux/cpumask.h
===================================================================
--- 2.6.7-rc2-mm2.orig/include/linux/cpumask.h 2004-06-03 05:56:00.000000000 -0700
+++ 2.6.7-rc2-mm2/include/linux/cpumask.h 2004-06-03 07:04:31.000000000 -0700
@@ -1,52 +1,379 @@
#ifndef __LINUX_CPUMASK_H
#define __LINUX_CPUMASK_H

+/*
+ * Cpumasks provide a bitmap suitable for representing the
+ * set of CPU's in a system, one bit position per CPU number.
+ *
+ * See detailed comments in the file linux/bitmap.h describing the
+ * data type on which these cpumasks are based.
+ *
+ * For details of cpumask_scnprintf() and cpumask_parse(),
+ * see bitmap_scnprintf() and bitmap_parse() in lib/bitmap.c.
+ *
+ * The available cpumask operations are:
+ *
+ * void cpu_set(cpu, mask) turn on bit 'cpu' in mask
+ * void cpu_clear(cpu, mask) turn off bit 'cpu' in mask
+ * void cpus_setall(mask) set all bits
+ * void cpus_clear(mask) clear all bits
+ * int cpu_isset(cpu, mask) true iff bit 'cpu' set in mask
+ * int cpu_test_and_set(cpu, mask) test and set bit 'cpu' in mask
+ *
+ * void cpus_and(dst, src1, src2) dst = src1 & src2 [intersection]
+ * void cpus_or(dst, src1, src2) dst = src1 | src2 [union]
+ * void cpus_xor(dst, src1, src2) dst = src1 ^ src2
+ * void cpus_andnot(dst, src1, src2) dst = src1 & ~src2
+ * void cpus_complement(dst, src) dst = ~src
+ *
+ * int cpus_equal(mask1, mask2) Does mask1 == mask2?
+ * int cpus_intersects(mask1, mask2) Do mask1 and mask2 intersect?
+ * int cpus_subset(mask1, mask2) Is mask1 a subset of mask2?
+ * int cpus_empty(mask) Is mask empty (no bits sets)?
+ * int cpus_full(mask) Is mask full (all bits sets)?
+ * int cpus_weight(mask) Hamming weigh - number of set bits
+ *
+ * void cpus_shift_right(dst, src, n) Shift right
+ * void cpus_shift_left(dst, src, n) Shift left
+ *
+ * int first_cpu(mask) Number lowest set bit, or NR_CPUS
+ * int next_cpu(cpu, mask) Next cpu past 'cpu', or NR_CPUS
+ *
+ * cpumask_t cpumask_of_cpu(cpu) Return cpumask with bit 'cpu' set
+ * CPU_MASK_ALL Initializer - all bits set
+ * CPU_MASK_NONE Initializer - no bits set
+ * unsigned long *cpus_addr(mask) Array of unsigned long's in mask
+ *
+ * int cpumask_scnprintf(buf, len, mask) Format cpumask for printing
+ * int cpumask_parse(ubuf, ulen, mask) Parse ascii string as cpumask
+ *
+ * int num_online_cpus() Number of online CPUs
+ * int num_possible_cpus() Number of all possible CPUs
+ * int cpu_online(cpu) Is some cpu online?
+ * int cpu_possible(cpu) Is some cpu possible?
+ * void cpu_set_online(cpu) set cpu in cpu_online_map
+ * void cpu_set_offline(cpu) clear cpu in cpu_online_map
+ * int any_online_cpu(mask) First online cpu in mask
+ *
+ * for_each_cpu_mask(cpu, mask) for-loop cpu over mask
+ * for_each_cpu(cpu) for-loop cpu over cpu_possible_map
+ * for_each_online_cpu(cpu) for-loop cpu over cpu_online_map
+ *
+ * Subtlety:
+ * 1) The 'type-checked' form of cpu_isset() causes gcc (3.3.2, anyway)
+ * to generate slightly worse code. Note for example the additional
+ * 40 lines of assembly code compiling the "for each possible cpu"
+ * loops buried in the disk_stat_read() macros calls when compiling
+ * drivers/block/genhd.c (arch i386, CONFIG_SMP=y). So use a simple
+ * one-line #define for cpu_isset(), instead of wrapping an inline
+ * inside a macro, the way we do the other calls.
+ */
+
#include <linux/threads.h>
#include <linux/bitmap.h>
-#include <asm/cpumask.h>
#include <asm/bug.h>

-#ifdef CONFIG_SMP
-
-extern cpumask_t cpu_online_map;
-extern cpumask_t cpu_possible_map;
-
-#define num_online_cpus() cpus_weight(cpu_online_map)
-#define num_possible_cpus() cpus_weight(cpu_possible_map)
-
-#define cpu_online(cpu) cpu_isset(cpu, cpu_online_map)
-#define cpu_possible(cpu) cpu_isset(cpu, cpu_possible_map)
+typedef struct { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t;
+extern cpumask_t _unused_cpumask_arg_;

-#define for_each_cpu_mask(cpu, mask) \
- for (cpu = first_cpu_const(mk_cpumask_const(mask)); \
- cpu < NR_CPUS; \
- cpu = next_cpu_const(cpu, mk_cpumask_const(mask)))
+#define cpu_set(cpu, dst) __cpu_set((cpu), &(dst))
+static inline void __cpu_set(int cpu, volatile cpumask_t *dstp)
+{
+ set_bit(cpu, dstp->bits);
+}
+
+#define cpu_clear(cpu, dst) __cpu_clear((cpu), &(dst))
+static inline void __cpu_clear(int cpu, volatile cpumask_t *dstp)
+{
+ clear_bit(cpu, dstp->bits);
+}
+
+#define cpus_setall(dst) __cpus_setall(&(dst), NR_CPUS)
+static inline void __cpus_setall(cpumask_t *dstp, int nbits)
+{
+ bitmap_fill(dstp->bits, nbits);
+}
+
+#define cpus_clear(dst) __cpus_clear(&(dst), NR_CPUS)
+static inline void __cpus_clear(cpumask_t *dstp, int nbits)
+{
+ bitmap_zero(dstp->bits, nbits);
+}
+
+/* No static inline type checking - see Subtlety (1) above. */
+#define cpu_isset(cpu, cpumask) test_bit((cpu), (cpumask).bits)
+
+#define cpu_test_and_set(cpu, cpumask) __cpu_test_and_set((cpu), &(cpumask))
+static inline int __cpu_test_and_set(int cpu, cpumask_t *addr)
+{
+ return test_and_set_bit(cpu, addr->bits);
+}
+
+#define cpus_and(dst, src1, src2) __cpus_and(&(dst), &(src1), &(src2), NR_CPUS)
+static inline void __cpus_and(cpumask_t *dstp, cpumask_t *src1p,
+ cpumask_t *src2p, int nbits)
+{
+ bitmap_and(dstp->bits, src1p->bits, src2p->bits, nbits);
+}
+
+#define cpus_or(dst, src1, src2) __cpus_or(&(dst), &(src1), &(src2), NR_CPUS)
+static inline void __cpus_or(cpumask_t *dstp, cpumask_t *src1p,
+ cpumask_t *src2p, int nbits)
+{
+ bitmap_or(dstp->bits, src1p->bits, src2p->bits, nbits);
+}
+
+#define cpus_xor(dst, src1, src2) __cpus_xor(&(dst), &(src1), &(src2), NR_CPUS)
+static inline void __cpus_xor(cpumask_t *dstp, cpumask_t *src1p,
+ cpumask_t *src2p, int nbits)
+{
+ bitmap_xor(dstp->bits, src1p->bits, src2p->bits, nbits);
+}
+
+#define cpus_andnot(dst, src1, src2) \
+ __cpus_andnot(&(dst), &(src1), &(src2), NR_CPUS)
+static inline void __cpus_andnot(cpumask_t *dstp, cpumask_t *src1p,
+ cpumask_t *src2p, int nbits)
+{
+ bitmap_andnot(dstp->bits, src1p->bits, src2p->bits, nbits);
+}
+
+#define cpus_complement(dst, src) __cpus_complement(&(dst), &(src), NR_CPUS)
+static inline void __cpus_complement(cpumask_t *dstp,
+ cpumask_t *srcp, int nbits)
+{
+ bitmap_complement(dstp->bits, srcp->bits, nbits);
+}
+
+#define cpus_equal(src1, src2) __cpus_equal(&(src1), &(src2), NR_CPUS)
+static inline int __cpus_equal(cpumask_t *src1p,
+ cpumask_t *src2p, int nbits)
+{
+ return bitmap_equal(src1p->bits, src2p->bits, nbits);
+}
+
+#define cpus_intersects(src1, src2) __cpus_intersects(&(src1), &(src2), NR_CPUS)
+static inline int __cpus_intersects(cpumask_t *src1p,
+ cpumask_t *src2p, int nbits)
+{
+ return bitmap_intersects(src1p->bits, src2p->bits, nbits);
+}
+
+#define cpus_subset(src1, src2) __cpus_subset(&(src1), &(src2), NR_CPUS)
+static inline int __cpus_subset(cpumask_t *src1p,
+ cpumask_t *src2p, int nbits)
+{
+ return bitmap_subset(src1p->bits, src2p->bits, nbits);
+}
+
+#define cpus_empty(src) __cpus_empty(&(src), NR_CPUS)
+static inline int __cpus_empty(cpumask_t *srcp, int nbits)
+{
+ return bitmap_empty(srcp->bits, nbits);
+}
+
+#define cpus_full(cpumask) __cpus_full(&(cpumask), NR_CPUS)
+static inline int __cpus_full(cpumask_t *srcp, int nbits)
+{
+ return bitmap_full(srcp->bits, nbits);
+}
+
+#define cpus_weight(cpumask) __cpus_weight(&(cpumask), NR_CPUS)
+static inline int __cpus_weight(cpumask_t *srcp, int nbits)
+{
+ return bitmap_weight(srcp->bits, nbits);
+}
+
+#define cpus_shift_right(dst, src, n) \
+ __cpus_shift_right(&(dst), &(src), (n), NR_CPUS)
+static inline void __cpus_shift_right(cpumask_t *dstp,
+ cpumask_t *srcp, int n, int nbits)
+{
+ bitmap_shift_right(dstp->bits, srcp->bits, n, nbits);
+}
+
+#define cpus_shift_left(dst, src, n) \
+ __cpus_shift_left(&(dst), &(src), (n), NR_CPUS)
+static inline void __cpus_shift_left(cpumask_t *dstp,
+ cpumask_t *srcp, int n, int nbits)
+{
+ bitmap_shift_left(dstp->bits, srcp->bits, n, nbits);
+}
+
+#define first_cpu(src) __first_cpu(&(src), NR_CPUS)
+static inline int __first_cpu(cpumask_t *srcp, int nbits)
+{
+ return find_first_bit(srcp->bits, nbits);
+}
+
+#define next_cpu(n, src) __next_cpu((n), &(src), NR_CPUS)
+static inline int __next_cpu(int n, cpumask_t *srcp, int nbits)
+{
+ return find_next_bit(srcp->bits, nbits, n+1);
+}
+
+#define cpumask_of_cpu(cpu) \
+({ \
+ typeof(_unused_cpumask_arg_) m; \
+ if (sizeof(m) == sizeof(unsigned long)) { \
+ m.bits[0] = 1UL<<(cpu); \
+ } else { \
+ cpus_clear(m); \
+ cpu_set((cpu), m); \
+ } \
+ m; \
+})
+
+#define CPU_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(NR_CPUS)
+
+#if NR_CPUS <= BITS_PER_LONG
+
+#define CPU_MASK_ALL \
+((cpumask_t) { { \
+ [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD \
+} })

-#define for_each_cpu(cpu) for_each_cpu_mask(cpu, cpu_possible_map)
-#define for_each_online_cpu(cpu) for_each_cpu_mask(cpu, cpu_online_map)
#else
-#define cpu_online_map cpumask_of_cpu(0)
-#define cpu_possible_map cpumask_of_cpu(0)

-#define num_online_cpus() 1
-#define num_possible_cpus() 1
+#define CPU_MASK_ALL \
+((cpumask_t) { { \
+ [0 ... BITS_TO_LONGS(NR_CPUS)-2] = ~0UL, \
+ [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD \
+} })

-#define cpu_online(cpu) ({ BUG_ON((cpu) != 0); 1; })
-#define cpu_possible(cpu) ({ BUG_ON((cpu) != 0); 1; })
-
-#define for_each_cpu(cpu) for (cpu = 0; cpu < 1; cpu++)
-#define for_each_online_cpu(cpu) for (cpu = 0; cpu < 1; cpu++)
#endif

+#define CPU_MASK_NONE \
+{ { \
+ [0 ... BITS_TO_LONGS(NR_CPUS)-1] = 0UL \
+} }
+
+#define cpus_addr(src) ((src).bits)
+
+#define cpumask_scnprintf(buf, len, src) \
+ __cpumask_scnprintf((buf), (len), &(src), NR_CPUS)
+static inline int __cpumask_scnprintf(char *buf, int len,
+ cpumask_t *srcp, int nbits)
+{
+ return bitmap_scnprintf(buf, len, srcp->bits, nbits);
+}
+
+#define cpumask_parse(ubuf, ulen, src) \
+ __cpumask_parse((ubuf), (ulen), &(src), NR_CPUS)
+static inline int __cpumask_parse(const char __user *buf, int len,
+ cpumask_t *srcp, int nbits)
+{
+ return bitmap_parse(buf, len, srcp->bits, nbits);
+}
+
+#if NR_CPUS > 1
+#define for_each_cpu_mask(cpu, mask) \
+ for ((cpu) = first_cpu(mask); \
+ (cpu) < NR_CPUS; \
+ (cpu) = next_cpu((cpu), (mask)))
+#else /* NR_CPUS == 1 */
+#define for_each_cpu_mask(cpu, mask) for ((cpu) = 0; (cpu) < 1; (cpu)++)
+#endif /* NR_CPUS */
+
+/*
+ * The following particular system cpumasks and operations manage
+ * possible, present and online cpus. Each of them is a fixed size
+ * bitmap of size NR_CPUS.
+ *
+ * #ifdef CONFIG_HOTPLUG_CPU
+ * cpu_possible_map - all NR_CPUS bits set
+ * cpu_present_map - has bit 'cpu' set iff cpu is populated
+ * cpu_online_map - has bit 'cpu' set iff cpu available to scheduler
+ * #else
+ * cpu_possible_map - has bit 'cpu' set iff cpu is populated
+ * cpu_present_map - copy of cpu_possible_map
+ * cpu_online_map - has bit 'cpu' set iff cpu available to scheduler
+ * #endif
+ *
+ * In either case, NR_CPUS is fixed at compile time, as the static
+ * size of these bitmaps. The cpu_possible_map is fixed at boot
+ * time, as the set of CPU id's that it is possible might ever
+ * be plugged in at anytime during the life of that system boot.
+ * The cpu_present_map is dynamic(*), representing which CPUs
+ * are currently plugged in. And cpu_online_map is the dynamic
+ * subset of cpu_present_map, indicating those CPUs available
+ * for scheduling.
+ *
+ * If HOTPLUG is enabled, then cpu_possible_map is forced to have
+ * all NR_CPUS bits set, otherwise it is just the set of CPUs that
+ * ACPI reports present at boot.
+ *
+ * If HOTPLUG is enabled, then cpu_present_map varies dynamically,
+ * depending on what ACPI reports as currently plugged in, otherwise
+ * cpu_present_map is just a copy of cpu_possible_map.
+ *
+ * (*) Well, cpu_present_map is dynamic in the hotplug case. If not
+ * hotplug, it's a copy of cpu_possible_map, hence fixed at boot.
+ *
+ * Subtleties:
+ * 1) UP arch's (NR_CPUS == 1, CONFIG_SMP not defined) hardcode
+ * assumption that their single CPU is online. The UP
+ * cpu_{online,possible,present}_maps are placebos. Changing them
+ * will have no useful affect on the following num_*_cpus()
+ * and cpu_*() macros in the UP case. This ugliness is a UP
+ * optimization - don't waste any instructions or memory references
+ * asking if you're online or how many CPUs there are if there is
+ * only one CPU.
+ * 2) Most SMP arch's #define some of these maps to be some
+ * other map specific to that arch. Therefore, the following
+ * must be #define macros, not inlines. To see why, examine
+ * the assembly code produced by the following. Note that
+ * set1() writes phys_x_map, but set2() writes x_map:
+ * int x_map, phys_x_map;
+ * #define set1(a) x_map = a
+ * inline void set2(int a) { x_map = a; }
+ * #define x_map phys_x_map
+ * main(){ set1(3); set2(5); }
+ */
+
+extern cpumask_t cpu_possible_map;
+extern cpumask_t cpu_online_map;
extern cpumask_t cpu_present_map;
-#define num_present_cpus() cpus_weight(cpu_present_map)
-#define cpu_present(cpu) cpu_isset(cpu, cpu_present_map)
-#define for_each_present_cpu(cpu) for_each_cpu_mask(cpu, cpu_present_map)

-#define cpumask_scnprintf(buf, buflen, map) \
- bitmap_scnprintf(buf, buflen, cpus_addr(map), NR_CPUS)
+#if NR_CPUS > 1
+#define num_online_cpus() cpus_weight(cpu_online_map)
+#define num_possible_cpus() cpus_weight(cpu_possible_map)
+#define num_present_cpus() cpus_weight(cpu_present_map)
+#define cpu_online(cpu) cpu_isset((cpu), cpu_online_map)
+#define cpu_possible(cpu) cpu_isset((cpu), cpu_possible_map)
+#define cpu_present(cpu) cpu_isset((cpu), cpu_present_map)
+#else
+#define num_online_cpus() 1
+#define num_possible_cpus() 1
+#define num_present_cpus() 1
+#define cpu_online(cpu) ((cpu) == 0)
+#define cpu_possible(cpu) ((cpu) == 0)
+#define cpu_present(cpu) ((cpu) == 0)
+#endif

-#define cpumask_parse(buf, buflen, map) \
- bitmap_parse(buf, buflen, cpus_addr(map), NR_CPUS)
+#define any_online_cpu(mask) \
+({ \
+ int cpu; \
+ for_each_cpu_mask(cpu, (mask)) \
+ if (cpu_online(cpu)) \
+ break; \
+ cpu; \
+})
+
+#define for_each_cpu(cpu) for_each_cpu_mask((cpu), cpu_possible_map)
+#define for_each_online_cpu(cpu) for_each_cpu_mask((cpu), cpu_online_map)
+#define for_each_present_cpu(cpu) for_each_cpu_mask((cpu), cpu_present_map)
+
+/* Begin obsolete cpumask operator emulation */
+#define cpu_isset_const(a,b) cpu_isset(a,b)
+#define cpumask_const_t cpumask_t
+#define cpus_coerce(m) (cpus_addr(m)[0])
+#define cpus_coerce_const cpus_coerce
+#define cpus_promote(x) ({ cpumask_t m; m.bits[0] = x; m; })
+#define cpus_weight_const cpus_weight
+#define first_cpu_const first_cpu
+#define mk_cpumask_const(x) x
+#define next_cpu_const next_cpu
+/* End of obsolete cpumask operator emulation */

#endif /* __LINUX_CPUMASK_H */
Index: 2.6.7-rc2-mm2/kernel/sched.c
===================================================================
--- 2.6.7-rc2-mm2.orig/kernel/sched.c 2004-06-03 05:56:00.000000000 -0700
+++ 2.6.7-rc2-mm2/kernel/sched.c 2004-06-03 06:42:03.000000000 -0700
@@ -3119,6 +3119,11 @@
cpumask_t cpu_present_map;
EXPORT_SYMBOL(cpu_present_map);

+#ifndef CONFIG_SMP
+cpumask_t cpu_online_map = CPU_MASK_ALL;
+cpumask_t cpu_possible_map = CPU_MASK_ALL;
+#endif
+
/**
* sys_sched_getaffinity - get the cpu affinity of a process
* @pid: pid of the process
Index: 2.6.7-rc2-mm2/arch/sparc64/kernel/irq.c
===================================================================
--- 2.6.7-rc2-mm2.orig/arch/sparc64/kernel/irq.c 2004-06-03 05:42:56.000000000 -0700
+++ 2.6.7-rc2-mm2/arch/sparc64/kernel/irq.c 2004-06-03 05:57:13.000000000 -0700
@@ -687,9 +687,10 @@
* Just Do It.
*/
struct irqaction *ap = bp->irq_info;
- cpumask_t cpu_mask = get_smpaff_in_irqaction(ap);
+ cpumask_t cpu_mask;
unsigned int buddy, ticks;

+ cpus_addr(cpu_mask)[0] = get_smpaff_in_irqaction(ap);
cpus_and(cpu_mask, cpu_mask, cpu_online_map);
if (cpus_empty(cpu_mask))
cpu_mask = cpu_online_map;
@@ -1206,9 +1207,10 @@
{
struct ino_bucket *bp = ivector_table + (long)data;
struct irqaction *ap = bp->irq_info;
- cpumask_t mask = get_smpaff_in_irqaction(ap);
+ cpumask_t mask;
int len;

+ cpus_addr(mask)[0] = get_smpaff_in_irqaction(ap);
if (cpus_empty(mask))
mask = cpu_online_map;

Index: 2.6.7-rc2-mm2/kernel/rcupdate.c
===================================================================
--- 2.6.7-rc2-mm2.orig/kernel/rcupdate.c 2004-06-03 05:46:28.000000000 -0700
+++ 2.6.7-rc2-mm2/kernel/rcupdate.c 2004-06-03 05:57:13.000000000 -0700
@@ -130,17 +130,14 @@
*/
static void rcu_start_batch(int next_pending)
{
- cpumask_t active;
-
if (next_pending)
rcu_ctrlblk.next_pending = 1;

if (rcu_ctrlblk.next_pending &&
rcu_ctrlblk.completed == rcu_ctrlblk.cur) {
/* Can't change, since spin lock held. */
- active = nohz_cpu_mask;
- cpus_complement(active);
- cpus_and(rcu_state.rcu_cpu_mask, cpu_online_map, active);
+ cpus_andnot(rcu_state.rcu_cpu_mask, cpu_online_map,
+ nohz_cpu_mask);
write_seqcount_begin(&rcu_ctrlblk.lock);
rcu_ctrlblk.next_pending = 0;
rcu_ctrlblk.cur++;

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@sgi.com> 1.650.933.1373