[Patch] common/kexec: Identify which cpu the kexec image is being executed on.

[Patch] common/kexec: Identify which cpu the kexec image is being executed on.

[Andrew Cooper]

A patch to this effect has been in XenServer for a little while, and has
proved to be a useful debugging point for servers which have different
behaviours depending when crashing on the non-bootstrap processor.

Moving the printk() from kexec_panic() to one_cpu_only() means that it will
not be printed multiple times in the case of multiple cpus racing on the kexec
path.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
CC: David Vrabel <david.vrabel@citrix.com>

---

I would like this to be considered for 4.4, given that it is a quite trivial
change, yet very useful information in the case of a crash.
---
 xen/common/kexec.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/common/kexec.c b/xen/common/kexec.c
index 481b0c2..5dcd487 100644
--- a/xen/common/kexec.c
+++ b/xen/common/kexec.c
@@ -265,6 +265,8 @@ static int noinline one_cpu_only(void)
     }
 
     set_bit(KEXEC_FLAG_IN_PROGRESS, &kexec_flags);
+    printk("Executing crash image on cpu%u\n", cpu);
+
     return 0;
 }
 
@@ -340,8 +342,6 @@ void kexec_crash(void)
     if ( !test_bit(KEXEC_IMAGE_CRASH_BASE + pos, &kexec_flags) )
         return;
 
-    printk("Executing crash image\n");
-
     kexecing = TRUE;
 
     if ( kexec_common_shutdown() != 0 )
-- 
1.7.10.4

Re: [Patch] common/kexec: Identify which cpu the kexec image is being executed on.

[David Vrabel]

On 06/01/14 11:59, Andrew Cooper wrote:
> A patch to this effect has been in XenServer for a little while, and has
> proved to be a useful debugging point for servers which have different
> behaviours depending when crashing on the non-bootstrap processor.
> 
> Moving the printk() from kexec_panic() to one_cpu_only() means that it will
> not be printed multiple times in the case of multiple cpus racing on the kexec
> path.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Keir Fraser <keir@xen.org>
> CC: Jan Beulich <JBeulich@suse.com>
> CC: David Vrabel <david.vrabel@citrix.com>

Acked-by: David Vrabel <david.vrabel@citrix.com>

One for 4.5 I think.

David

Re: [Patch] common/kexec: Identify which cpu the kexec image is being executed on.

[Jan Beulich]

>>> On 06.01.14 at 12:59, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
> --- a/xen/common/kexec.c
> +++ b/xen/common/kexec.c
> @@ -265,6 +265,8 @@ static int noinline one_cpu_only(void)
>      }
>  
>      set_bit(KEXEC_FLAG_IN_PROGRESS, &kexec_flags);
> +    printk("Executing crash image on cpu%u\n", cpu);
> +
>      return 0;
>  }
>  

With the calling function also being used from kexec_reboot(),
printing "crash image" here isn't really correct afaict.

Jan

> @@ -340,8 +342,6 @@ void kexec_crash(void)
>      if ( !test_bit(KEXEC_IMAGE_CRASH_BASE + pos, &kexec_flags) )
>          return;
>  
> -    printk("Executing crash image\n");
> -
>      kexecing = TRUE;
>  
>      if ( kexec_common_shutdown() != 0 )
> -- 
> 1.7.10.4

Re: [Patch] common/kexec: Identify which cpu the kexec image is being executed on.

[David Vrabel]

On 07/01/14 14:29, Jan Beulich wrote:
>>>> On 06.01.14 at 12:59, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> --- a/xen/common/kexec.c
>> +++ b/xen/common/kexec.c
>> @@ -265,6 +265,8 @@ static int noinline one_cpu_only(void)
>>      }
>>  
>>      set_bit(KEXEC_FLAG_IN_PROGRESS, &kexec_flags);
>> +    printk("Executing crash image on cpu%u\n", cpu);
>> +
>>      return 0;
>>  }
>>  
> 
> With the calling function also being used from kexec_reboot(),
> printing "crash image" here isn't really correct afaict.

Good point.

David