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From:   Qian Cai <cai@lca.pw>
Mime-Version: 1.0 (1.0)
Subject: Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages()
Date:   Sat, 5 Oct 2019 18:38:38 -0400
Message-Id: <615D1FE9-C16A-4FD5-A113-1C50AB3F0222@lca.pw>
References: <20191005142232.e08976cf8905824fad0533ff@linux-foundation.org>
Cc:     Michal Hocko <mhocko@kernel.org>,
        Anshuman Khandual <Anshuman.Khandual@arm.com>,
        linux-mm@kvack.org, Vlastimil Babka <vbabka@suse.cz>,
        Oscar Salvador <osalvador@suse.de>,
        Mel Gorman <mgorman@techsingularity.net>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Pavel Tatashin <pavel.tatashin@microsoft.com>,
        linux-kernel@vger.kernel.org
In-Reply-To: <20191005142232.e08976cf8905824fad0533ff@linux-foundation.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Oct 5, 2019, at 5:22 PM, Andrew Morton <akpm@linux-foundation.org> wrot=
e:
>=20
> Apparently some console drivers can do memory allocation on the printk()
> path.
>=20
> This behavior is daft, IMO.  Have we identified which ones and looked
> into fixing them?

Not necessary that simple. It is more of 2+ CPUs required to trigger the dea=
dlock. Please see my v2 patch I sent which has all the information. Especial=
ly, the thread link included there which contains a few lockdep splat traces=
 and the s390 one in the patch description.=