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Date:   Thu, 4 Jul 2019 12:32:18 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     Qian Cai <cai@lca.pw>, axboe@kernel.dk, hch@lst.de,
        peterz@infradead.org, gkohli@codeaurora.org, mingo@redhat.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH] swap_readpage: avoid blk_wake_io_task() if !synchronous
Message-Id: <20190704123218.87a763f771efad158e1b0a89@linux-foundation.org>
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        <20190704160301.GA5956@redhat.com>
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On Thu, 4 Jul 2019 18:03:01 +0200 Oleg Nesterov <oleg@redhat.com> wrote:

> swap_readpage() sets waiter = bio->bi_private even if synchronous = F,
> this means that the caller can get the spurious wakeup after return. This
> can be fatal if blk_wake_io_task() does set_current_state(TASK_RUNNING)
> after the caller does set_special_state(), in the worst case the kernel
> can crash in do_task_dead().

I think we need a Fixes: and a cc:stable here?

IIRC, we're fixing 0619317ff8baa2 ("block: add polled wakeup task helper").