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Date:   Mon, 14 Sep 2020 17:50:32 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Qian Cai <cai@redhat.com>
Cc:     linux-mm@kvack.org, intel-gfx@lists.freedesktop.org,
        Huang Ying <ying.huang@intel.com>,
        Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org,
        Chris Wilson <chris@chris-wilson.co.uk>,
        William Kucharski <william.kucharski@oracle.com>,
        Johannes Weiner <hannes@cmpxchg.org>, cgroups@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Matthew Auld <matthew.auld@intel.com>
Subject: Re: [PATCH v2 3/8] mm: Optimise madvise WILLNEED
Message-ID: <20200914165032.GS6583@casper.infradead.org>
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 <20200910183318.20139-4-willy@infradead.org>
 <c48c5eaa09d1ea5b78b12b545c034d1e937c49ba.camel@redhat.com>
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On Mon, Sep 14, 2020 at 12:17:07PM -0400, Qian Cai wrote:
> Reverting the "Return head pages from find_*_entry" patchset [1] up to this
> patch fixed the issue that LTP madvise06 test [2] would trigger endless soft-
> lockups below. It does not help after applied patches fixed other separate
> issues in the patchset [3][4].

Thanks for the report.  Could you try this?

diff --git a/mm/madvise.c b/mm/madvise.c
index 96189acd6969..2d9ceccb338d 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -234,6 +234,7 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 
 		if (!xa_is_value(page))
 			continue;
+		xas_pause(&xas);
 		rcu_read_unlock();
 
 		swap = radix_to_swp_entry(page);
@@ -243,7 +244,6 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 			put_page(page);
 
 		rcu_read_lock();
-		xas_reset(&xas);
 	}
 	rcu_read_unlock();