linux-kernel - Re: [PATCH] mm: might

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Message-ID: <a90aa8fc-0612-3107-93c6-9e4b706785db@oracle.com>
Date:   Tue, 6 Mar 2018 16:48:31 -0500
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Steven Sistare <steven.sistare@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Masayoshi Mizuma <m.mizuma@...fujitsu.com>,
        Michal Hocko <mhocko@...e.com>,
        Catalin Marinas <catalin.marinas@....com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Gioh Kim <gi-oh.kim@...fitbricks.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Yaowei Bai <baiyaowei@...s.chinamobile.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Paul Burton <paul.burton@...s.com>,
        Miles Chen <miles.chen@...iatek.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH] mm: might_sleep warning

> 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