From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shawn Lin Subject: Re: [PATCH] f2fs: avoid hungtask problem caused by losing wake_up Date: Tue, 23 Feb 2016 17:32:04 +0800 Message-ID: <56CC2714.7040901@kernel-upstream.org> References: <1456200476-9811-1-git-send-email-heyunlei@huawei.com> <009501d16dfd$52a518c0$f7ef4a40$@samsung.com> <56CC0410.50103@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1aY9Zx-0007hU-Ls for linux-f2fs-devel@lists.sourceforge.net; Tue, 23 Feb 2016 09:48:25 +0000 Received: from mr213139.mail.yeah.net ([223.252.213.139]) by sog-mx-3.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1aY9Zv-0007HZ-My for linux-f2fs-devel@lists.sourceforge.net; Tue, 23 Feb 2016 09:48:25 +0000 In-Reply-To: <56CC0410.50103@huawei.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: He YunLei , Chao Yu , jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net Cc: 'Biao He' , shawn.lin@rock-chips.com On 2016/2/23 15:02, He YunLei wrote: > On 2016/2/23 13:44, Chao Yu wrote: >> Hi Yunlei, > Hi Chao, >> >>> -----Original Message----- >>> From: Yunlei He [mailto:heyunlei@huawei.com] >>> Sent: Tuesday, February 23, 2016 12:08 PM >>> To: chao2.yu@samsung.com; jaegeuk@kernel.org; linux-f2fs-devel@lists.sourceforge.net >>> Cc: bintian.wang@huawei.com; Yunlei He; Biao He >>> Subject: [f2fs-dev] [PATCH] f2fs: avoid hungtask problem caused by losing wake_up >>> >>> The D state of wait_on_all_pages_writeback should be waken by >>> function f2fs_write_end_io when all writeback pages have been >>> succesfully written to device. It's possible that wake_up comes >>> between get_pages and io_schedule. Maybe in this case it will >>> lost wake_up and still in D state even if all pages have been >>> write back to device, and finally, the whole system will be into >>> the hungtask state. >> >> I haven't encountered such issue so far, do you suffer this in real >> world? >> > yes, I have encounter it, the whole file system is blocked at function > wait_on_all_pages_writeback beyond 120s when write cp, and no error reported > by storage device driver. Hi YunLei Interesting... How to prove the page isn't been locked by storage block layer which doesn't finish the related bio? I suffer that case before, but then I solve it by seting a timer to break my mmc driver while missing some important interrupts(chip problem) for data-transfer to finish the io queue by mmcqd. Another thing, why making 5HZ for timeout? why not 10HZ ,15HZ... io_schedule_timeout(5*HZ); >>> >>> if (!get_pages(sbi, F2FS_WRITEBACK)) >>> break; >>> <--------- wake_up >> >> wake_up will put all tasks linked in sbi->cp_wait on run-queue, so >> here it should be save to call io_schedule, after being rescheduled, >> it will get the chance to check above condition to break out. >> >> Thanks, > > Here, we just doubt something weird may cause wait_on_all_pages_writeback > could not be waken. Wake_up trigger only one time by last bio's end_io > function, if the thread happen to miss it, the thread will be in D state > forever. So we change the code to make wait_on_all_pages_writeback awaken > periodically, then check the condition. > >> >>> io_schedule(); >>> >>> Signed-off-by: Yunlei He >>> Signed-off-by: Biao He >>> --- >>> fs/f2fs/checkpoint.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c >>> index 2bac8a1..f55355d 100644 >>> --- a/fs/f2fs/checkpoint.c >>> +++ b/fs/f2fs/checkpoint.c >>> @@ -920,7 +920,7 @@ static void wait_on_all_pages_writeback(struct f2fs_sb_info *sbi) >>> if (!get_pages(sbi, F2FS_WRITEBACK)) >>> break; >>> >>> - io_schedule(); >>> + io_schedule_timeout(5*HZ); >>> } >>> finish_wait(&sbi->cp_wait, &wait); >>> } >>> -- >>> 1.9.1 >> >> >> >> . >> > > > ------------------------------------------------------------------------------ > Site24x7 APM Insight: Get Deep Visibility into Application Performance > APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month > Monitor end-to-end web transactions and take corrective actions now > Troubleshoot faster and improve end-user experience. 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