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Subject: Re: [PATCH] mm: might_sleep warning
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References: <20180306192022.28289-1-pasha.tatashin@oracle.com>
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From: Pavel Tatashin <pasha.tatashin@oracle.com>
Message-ID: <a90aa8fc-0612-3107-93c6-9e4b706785db@oracle.com>
Date: Tue, 6 Mar 2018 16:48:31 -0500
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> That's why page_alloc_init_late() needs spin_lock_irq().  If a CPU is
> holding deferred_zone_grow_lock with enabled interrupts and an
> interrupt comes in on that CPU and the CPU runs deferred_grow_zone() in
> its interrupt handler, we deadlock.
> 
> lockdep knows about this bug and should have reported it.
> 

I see what you are saying. Yes you are correct, we need spin_lock_irq() 
in page_alloc_init_late(). I will update the patch. I am not sure why 
lockdep has not reported it. May be it is initialized after this code is 
executed?

Thank you,
Pavel