[PATCH 1/4] 2.6.2-rc2-mm2 CPU Hotplug: cpu_active_map

From: Rusty Russell (rusty_at_rustcorp.com.au)
Date: 01/31/04

  • Next message: Rusty Russell: "[PATCH 3/4] 2.6.2-rc2-mm2 CPU Hotplug: The Core" 
    To: akpm@osdl.org
Date:	Sun, 01 Feb 2004 01:16:35 +1100

    Hi Andrew et al.

            Forward ported to -mm tree, so there might still be bugs.
    Wanted to get these aired more widely. Especially get Nick exposed to
    the sched parts.

    Name: Create cpu_active_map
    Author: Rusty Russell
    Status: Booted on 2.6.2-rc2-bk2

    D: When CPUs are going down, there is a time when cpu_online(cpu) is
    D: false, but they are still scheduling and responding to interrupts
    D: (we are migrating things off the CPU, shutting down per-cpu
    D: threads, etc). It turns out that RCU cares about these CPUs, so
    D: the decision was made to expose this mask (previously internal to x86,
    D: and only used for IPIs).
    D:
    D: The semantics of this mask are as follows:
    D: 1) For platforms without hot unplug of CPUs: cpu_active_map ==
    D: cpu_online_map.
    D: 2) For the others, they are equal except for a CPU which is going
    D: down: cpu_online_map gets cleared by __cpu_disable(), cpu_ipi_map
    D: gets cleared in __cpu_die() once the CPU is no longer responding
    D: to interrupts.

    diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .25707-linux-2.6.0-test11-bk7/include/linux/cpumask.h .25707-linux-2.6.0-test11-bk7.updated/include/linux/cpumask.h
    --- .25707-linux-2.6.0-test11-bk7/include/linux/cpumask.h 2003-12-10 13:58:18.000000000 +1100
    +++ .25707-linux-2.6.0-test11-bk7.updated/include/linux/cpumask.h 2003-12-10 14:01:29.000000000 +1100
    @@ -43,6 +43,13 @@ typedef unsigned long cpumask_t;
     extern cpumask_t cpu_online_map;
     extern cpumask_t cpu_possible_map;
     
    +#ifdef CONFIG_HOTPLUG_CPU
    +/* Online, or on its way down but still receiving interrupts. */
    +extern cpumask_t cpu_active_map;
    +#else
    +#define cpu_active_map cpu_online_map
    +#endif
    +
     #define num_online_cpus() cpus_weight(cpu_online_map)
     #define cpu_online(cpu) cpu_isset(cpu, cpu_online_map)
     #define cpu_possible(cpu) cpu_isset(cpu, cpu_possible_map)
    diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .25707-linux-2.6.0-test11-bk7/kernel/rcupdate.c .25707-linux-2.6.0-test11-bk7.updated/kernel/rcupdate.c
    --- .25707-linux-2.6.0-test11-bk7/kernel/rcupdate.c 2003-12-10 13:58:19.000000000 +1100
    +++ .25707-linux-2.6.0-test11-bk7.updated/kernel/rcupdate.c 2003-12-10 14:01:03.000000000 +1100
    @@ -110,7 +110,7 @@ static void rcu_start_batch(long newbatc
                 !cpus_empty(rcu_ctrlblk.rcu_cpu_mask)) {
                     return;
             }
    - rcu_ctrlblk.rcu_cpu_mask = cpu_online_map;
    + rcu_ctrlblk.rcu_cpu_mask = cpu_active_map;
     }
     
     /* 

    --
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
-
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