[Xen-devel] RE: [PATCH] Fix cpu offline bug

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

Keir,

Thanks for comments and update!
However, I think we still need update it a little :)

=============================
Fix cpu offline bug

Remove BUG_ON since it's of some risk, considering the small time window:
cpu0 read (cpu_state) --> offlining cpu write (cpu_state) --> cpu0 read 
(cpu_state)

Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>

diff -r 1ecb840bea17 xen/arch/x86/smpboot.c
--- a/xen/arch/x86/smpboot.c    Sat Mar 05 23:30:29 2022 +0800
+++ b/xen/arch/x86/smpboot.c    Sun Mar 06 01:21:34 2022 +0800
@@ -864,7 +864,6 @@ void __cpu_die(unsigned int cpu)

     while ( cpu_state != CPU_STATE_DEAD )
     {
-        BUG_ON(cpu_state != CPU_STATE_DYING);
         mdelay(100);
         cpu_relax();
         process_pending_softirqs();
=============================

Thanks,
Jinsong



Keir Fraser wrote:
> On 04/03/2011 10:22, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> 
>> Fix cpu offline bug
>> 
>> At current xen, when cpu offline, cpu0 will wait the 1st cpu offline;
>> However, if offline 2nd, 3rd, ... cpu, cpu0 will not wait it.
>> This patch is used to fix the bug.
> 
> Alternative fix applied tio unstable and 4.1-testing. The fix below
> doesn't account for the fact that cpu_state can also ==
> CPU_STATE_DEAD after an (unsuccessful) CPU online operation.
> 
>  -- Keir
> 
>> Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
>> 
>> diff -r d1631540bcc4 xen/arch/x86/smpboot.c
>> --- a/xen/arch/x86/smpboot.c Tue Jan 18 17:23:24 2011 +0000
>> +++ b/xen/arch/x86/smpboot.c Sat Feb 12 03:48:09 2011 +0800
>> @@ -78,7 +78,8 @@ static enum cpu_state {
>>      CPU_STATE_INIT,     /* master -> slave: Early bringup phase 1 */
>>      CPU_STATE_CALLOUT,  /* master -> slave: Early bringup phase 2 */
>>      CPU_STATE_CALLIN,   /* slave -> master: Completed phase 2 */
>> -    CPU_STATE_ONLINE    /* master -> slave: Go fully online now. */
>> +    CPU_STATE_ONLINE,   /* master -> slave: Go fully online now. */
>> +    CPU_STATE_STAY      /* after slave dead, global cpu_state stay
>>  here */  } cpu_state; #define set_cpu_state(state) do { mb();
>> cpu_state = (state); } while (0) 
>> 
>> @@ -867,6 +868,8 @@ void __cpu_die(unsigned int cpu)
>>          if ( (++i % 10) == 0 )
>>              printk(KERN_ERR "CPU %u still not dead...\n", cpu);    
>> } +
>> +    set_cpu_state(CPU_STATE_STAY);
>>  }
>> 
>>  int cpu_add(uint32_t apic_id, uint32_t acpi_id, uint32_t pxm)


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel