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Date: Thu, 4 Jul 2019 14:15:33 -0700 (PDT) From: Hugh Dickins <hughd@...gle.com> To: Andrew Morton <akpm@...ux-foundation.org> cc: Oleg Nesterov <oleg@...hat.com>, Qian Cai <cai@....pw>, axboe@...nel.dk, hch@....de, peterz@...radead.org, gkohli@...eaurora.org, mingo@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com> Subject: Re: [PATCH] swap_readpage: avoid blk_wake_io_task() if !synchronous On Thu, 4 Jul 2019, Andrew Morton wrote: > On Thu, 4 Jul 2019 18:03:01 +0200 Oleg Nesterov <oleg@...hat.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"). Yes, you are right. But catch me by surprise: I had been thinking this was a 5.2 regression. I guess something in 5.2 (doesn't matter what) has made it significantly easier to hit: but now I look at old records, see that I hit it once on 5.0-rc1, then never again until 5.2. Thanks, and to Oleg, Hugh
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