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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id g124sm168098qkf.55.2019.05.29.12.07.01 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 May 2019 12:07:02 -0700 (PDT) From: Qian Cai To: akpm@linux-foundation.org Cc: axboe@kernel.dk, hch@lst.de, peterz@infradead.org, oleg@redhat.com, gkohli@codeaurora.org, mingo@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH] mm/page_io: fix a crash in do_task_dead() Date: Wed, 29 May 2019 15:06:53 -0400 Message-Id: <1559156813-30681-1-git-send-email-cai@lca.pw> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The commit 0619317ff8ba ("block: add polled wakeup task helper") replaced wake_up_process() with blk_wake_io_task() in end_swap_bio_read() which triggers a crash when running heavy swapping workloads. [T114538] kernel BUG at kernel/sched/core.c:3462! [T114538] Process oom01 (pid: 114538, stack limit = 0x000000004f40e0c1) [T114538] Call trace: [T114538] do_task_dead+0xf0/0xf8 [T114538] do_exit+0xd5c/0x10fc [T114538] do_group_exit+0xf4/0x110 [T114538] get_signal+0x280/0xdd8 [T114538] do_notify_resume+0x720/0x968 [T114538] work_pending+0x8/0x10 This is because shortly after set_special_state(TASK_DEAD), end_swap_bio_read() is called from an interrupt handler that revive the task state to TASK_RUNNING causes __schedule() to return and trip the BUG() later. [ C206] Call trace: [ C206] dump_backtrace+0x0/0x268 [ C206] show_stack+0x20/0x2c [ C206] dump_stack+0xb4/0x108 [ C206] blk_wake_io_task+0x7c/0x80 [ C206] end_swap_bio_read+0x22c/0x31c [ C206] bio_endio+0x3d8/0x414 [ C206] dec_pending+0x280/0x378 [dm_mod] [ C206] clone_endio+0x128/0x2ac [dm_mod] [ C206] bio_endio+0x3d8/0x414 [ C206] blk_update_request+0x3ac/0x924 [ C206] scsi_end_request+0x54/0x350 [ C206] scsi_io_completion+0xf0/0x6f4 [ C206] scsi_finish_command+0x214/0x228 [ C206] scsi_softirq_done+0x170/0x1a4 [ C206] blk_done_softirq+0x100/0x194 [ C206] __do_softirq+0x350/0x790 [ C206] irq_exit+0x200/0x26c [ C206] handle_IPI+0x2e8/0x514 [ C206] gic_handle_irq+0x224/0x228 [ C206] el1_irq+0xb8/0x140 [ C206] _raw_spin_unlock_irqrestore+0x3c/0x74 [ C206] do_task_dead+0x88/0xf8 [ C206] do_exit+0xd5c/0x10fc [ C206] do_group_exit+0xf4/0x110 [ C206] get_signal+0x280/0xdd8 [ C206] do_notify_resume+0x720/0x968 [ C206] work_pending+0x8/0x10 Before the offensive commit, wake_up_process() will prevent this from happening by taking the pi_lock and bail out immediately if TASK_DEAD is set. if (!(p->state & TASK_NORMAL)) goto out; Fixes: 0619317ff8ba ("block: add polled wakeup task helper") Signed-off-by: Qian Cai --- mm/page_io.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/page_io.c b/mm/page_io.c index 2e8019d0e048..dc2d3e037ccf 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -140,7 +140,8 @@ static void end_swap_bio_read(struct bio *bio) unlock_page(page); WRITE_ONCE(bio->bi_private, NULL); bio_put(bio); - blk_wake_io_task(waiter); + /* end_swap_bio_read() could be called from an interrupt handler. */ + wake_up_process(waiter); put_task_struct(waiter); } -- 1.8.3.1