Re: [Xen-devel] Xen PVM: Strange lockups when running PostgreSQL load

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.10.12 at 12:20, Stefan Bader <stefan.bader@xxxxxxxxxxxxx> wrote:
> On 18.10.2012 09:48, Ian Campbell wrote:
>> spinning_lock() returns the old lock which the caller is expected to
>> remember and replace via unspinning_lock() -- it effectively implements
>> a stack of locks which are being waited on. xen_spin_lock_slow (the only
>> caller0 appears to do this correctly from a brief inspection.
> 
> Yes, just *when* can there be a stack of locks (spinlocks). The poll_irq
> hypercall seems to be an active (in the sense of not preemting to another 
> task)
> process. How could there be a situation that another lock (on the same cpu 
> is tried to be taken).

Obviously when this is an acquire not disabling interrupts, and
an interrupt comes in while in the poll hypercall (or about to go
there, or just having come back from one).

Jan


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