From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans de Goede Subject: 4.8-rc1 REGRESSION mmc-blk triggers WARN_ON(!host->claimed), related to: "drivers: use req op accessor" ? Date: Sun, 21 Aug 2016 17:15:43 +0200 Message-ID: <6e68ae5a-4b79-a636-2c46-5726cf2cc44b@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50806 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753190AbcHUPWK (ORCPT ); Sun, 21 Aug 2016 11:22:10 -0400 Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Ulf Hansson , Mike Christie , Jens Axboe , regressions@leemhuis.info Cc: "linux-mmc@vger.kernel.org" Hi All, With 4.8-rc1 I'm seeing WARN_ON(!host->claimed) triggering in both mmc_start_request() as well as in mmc_release_host(). The first indicating that we're executing mmc commands without doing mmc_claim_host() and the second one indicating that we're releasing the host without having claimed it first. The backtraces all point to mmc_blk_issue_rq(). I've done a very naive hack / workaround: --- a/drivers/mmc/card/block.c +++ b/drivers/mmc/card/block.c @@ -2151,9 +2151,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req) struct mmc_host *host = card->host; unsigned long flags; - if (req && !mq->mqrq_prev->req) - /* claim host only for the first request */ - mmc_get_card(card); + mmc_get_card(card); ret = mmc_blk_part_switch(card, md); if (ret) { @@ -2190,15 +2188,8 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req) } out: - if ((!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) || - mmc_req_is_special(req)) - /* - * Release host when there are no more requests - * and after special request(discard, flush) is done. - * In case sepecial request, there is no reentry to - * the 'mmc_blk_issue_rq' with 'mqrq_prev->req'. - */ - mmc_put_card(card); + mmc_put_card(card); + return ret; } Which fixes this, further pointing to the somewhat magical claim / release code in mmc_blk_issue_rq() being the culprit. Looking at recent commits these 2 stand out as possible causes of this: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c2df40dfb8c015211ec55f4b1dd0587f875c7b34 https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3a5e02ced11e22ecd9da3d6710afe15bcfee1d10 I've the feeling that one of these is making mmc_blk_issue_rq() not claiming the host while it should do so ... Maybe instead of the magic at the top we need a simple bool to check if the host is already claimed by the mmc_queue code ? I can reproduce the WARN_ON's pretty much at will (running 4.8-rc1 on Allwinner ARM devices with rootfs on a sdcard), let me know if you've a fix you want me to test. Regards, Hans p.s. Besides the WARN_ON triggering another side-effect of this is that the machines will hang at poweroff.