Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a0d8cdb652d35af9319a9e0fb7134de2a276c636
Commit:     a0d8cdb652d35af9319a9e0fb7134de2a276c636
Parent:     12d00f6a121877235a5cacc56386936dd9bb81af
Author:     Akinobu Mita <[EMAIL PROTECTED]>
AuthorDate: Thu Oct 18 03:05:12 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Oct 18 14:37:21 2007 -0700

    cpu hotplug: cpu: deliver CPU_UP_CANCELED only to NOTIFY_OKed callbacks 
with CPU_UP_PREPARE
    
    The functions in a CPU notifier chain is called with CPU_UP_PREPARE event
    before making the CPU online.  If one of the callback returns NOTIFY_BAD, it
    stops to deliver CPU_UP_PREPARE event, and CPU online operation is canceled.
    Then CPU_UP_CANCELED event is delivered to the functions in a CPU notifier
    chain again.
    
    This CPU_UP_CANCELED event is delivered to the functions which have been
    called with CPU_UP_PREPARE, not delivered to the functions which haven't 
been
    called with CPU_UP_PREPARE.
    
    The problem that makes existing cpu hotplug error handlings complex is that
    the CPU_UP_CANCELED event is delivered to the function that has returned
    NOTIFY_BAD, too.
    
    Usually we don't expect to call destructor function against the object that
    has failed to initialize.  It is like:
    
        err = register_something();
        if (err) {
                unregister_something();
                return err;
        }
    
    So it is natural to deliver CPU_UP_CANCELED event only to the functions that
    have returned NOTIFY_OK with CPU_UP_PREPARE event and not to call the 
function
    that have returned NOTIFY_BAD.  This is what this patch is doing.
    
    Otherwise, every cpu hotplug notifiler has to track whether notifiler event 
is
    failed or not for each cpu.  (drivers/base/topology.c is doing this with
    topology_dev_map)
    
    Similary this patch makes same thing with CPU_DOWN_PREPARE and 
CPU_DOWN_FAILED
    evnets.
    
    Acked-by: Rusty Russell <[EMAIL PROTECTED]>
    Signed-off-by: Akinobu Mita <[EMAIL PROTECTED]>
    Cc: Gautham R Shenoy <[EMAIL PROTECTED]>
    Cc: Oleg Nesterov <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 kernel/cpu.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 38033db..a21f71a 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -150,6 +150,7 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
        err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
                                        hcpu, -1, &nr_calls);
        if (err == NOTIFY_BAD) {
+               nr_calls--;
                __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
                                          hcpu, nr_calls, NULL);
                printk("%s: attempt to take down CPU %u failed\n",
@@ -233,6 +234,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int 
tasks_frozen)
        ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
                                                        -1, &nr_calls);
        if (ret == NOTIFY_BAD) {
+               nr_calls--;
                printk("%s: attempt to bring up CPU %u failed\n",
                                __FUNCTION__, cpu);
                ret = -EINVAL;
-
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