Peter Zijlstra wrote:
I added some debug statements within the above code. This is a 2 cpu machine.

XMON dest_cpu = 1024 . dead_cpu = 1 . nr_cpu_ids = 2
XMON dest_cpu = 1024 XMON dest_cpu = 1024 . dead_cpu = 1
XMON dest_cpu = 1024 . dead_cpu = 1 . nr_cpu_ids = 2
XMON dest_cpu = 1024 XMON dest_cpu = 1024 . dead_cpu = 1
XMON dest_cpu = 1024 . dead_cpu = 1 . nr_cpu_ids = 2
XMON dest_cpu = 1024 XMON dest_cpu = 1024 . dead_cpu = 1

Seems to me that the control is stuck in an infinite loop and hence the
machine appears to be in hung state. The dest_cpu value is always 1024
and never changes, which result in an infinite loop.

In working scenario the o/p is something on the following lines

XMON dest_cpu = 1024 . dead_cpu = 1 . nr_cpu_ids = 2
XMON dest_cpu = 0 XMON dest_cpu = 1024 . dead_cpu = 1 . nr_cpu_ids = 2 XMON dest_cpu = 0 XMON dest_cpu = 1024 . dead_cpu = 1 . nr_cpu_ids = 2 XMON dest_cpu = 0
Let me know if i should try to record any specific value ?

Could you possibly print the two masks themselves? cpumask_scnprintf()
and friend come in handy for this.

The dest_cpu=1024 thing seem to suggest the intersection between
p->cpus_allowed and cpu_active_mask is empty for some reason, even
though we forcefully reset p->cpus_allowed to the full set using
cpuset_cpus_allowed_locked().
So here is the data related to the two masks.

cpu_active_mask = 00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000
XMON dest_cpu = 1024

while p->cpus_allowed =  00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000001
XMON dest_cpu = 1024

In working scenario the above data looks like

cpu_active_mask = 00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000002
XMON dest_cpu = 1

while p->cpus_allowed =  00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,
00000000,00000000,00000002
XMON dest_cpu = 1


hope i got the data correct.

Thanks
-Sachin


--

---------------------------------
Sachin Sant
IBM Linux Technology Center
India Systems and Technology Labs
Bangalore, India
---------------------------------

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