Hi Ming, On 02.07.2020 03:22, Ming Lei wrote: > On Wed, Jul 01, 2020 at 04:16:32PM +0200, Marek Szyprowski wrote: >> On 01.07.2020 15:45, Ming Lei wrote: >>> On Wed, Jul 01, 2020 at 03:01:03PM +0200, Marek Szyprowski wrote: >>>> On 29.06.2020 11:47, Ming Lei wrote: >>>>> It is natural to release driver tag when this request is completed by >>>>> LLD or device since its purpose is for LLD use. >>>>> >>>>> One big benefit is that the released tag can be re-used quicker since >>>>> bio_endio() may take too long. >>>>> >>>>> Meantime we don't need to release driver tag for flush request. >>>>> >>>>> Cc: Christoph Hellwig <hch@xxxxxx> >>>>> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> >>>> This patch landed recently in linux-next as commit 36a3df5a4574. Sadly >>>> it causes a regression on one of my test systems (ARM 32bit, Samsung >>>> Exynos5422 SoC based Odroid XU3 board with eMMC). The system boots fine >>>> and then after a few seconds every executed command hangs. No >>>> panic/ops/any other message. I will try to provide more information asap >>>> I find something to share. Simple reverting it in linux-next is not >>>> possible due to dependencies. >>> What is the exact eMMC's driver code(include the host driver)? >> dwmmc-exynos (drivers/mmc/host/dw_mmc-exynos.c) > Hi, > > Just take a quick look at mmc code, there are only two req->tag > consumers: > > 1) cqhci_tag > cqhci_tag > cqhci_request > host->cqe_ops->cqe_request > mmc_cqe_start_req > cqhci_timeout > > 2) mmc_hsq_request > mmc_hsq_request > host->cqe_ops->cqe_request > mmc_cqe_start_req > > mmc_cqe_start_req() is called before issuing this request to hardware, > so completion won't happen when the tag is used in mmc_cqe_start_req(). > > cqhci_timeout() may race with normal completion, however looks the > following code can handle the race correctly: > > spin_lock_irqsave(&cq_host->lock, flags); > timed_out = slot->mrq == mrq; > > So still no idea why the commit causes the trouble for mmc. > > Do you know it is cqhci or mmc_hsh which works for dw_mmc-exynos? > And can you apply the following patch and see if warning can be > triggered? > > diff --git a/drivers/mmc/host/cqhci.c b/drivers/mmc/host/cqhci.c > index 75934f3c117e..2cb49ecfbf34 100644 > --- a/drivers/mmc/host/cqhci.c > +++ b/drivers/mmc/host/cqhci.c > @@ -612,6 +612,7 @@ static int cqhci_request(struct mmc_host *mmc, struct mmc_request *mrq) > goto out_unlock; > } > > + WARN_ON_ONCE(cq_host->slot[tag].mrq); > cq_host->slot[tag].mrq = mrq; > cq_host->slot[tag].flags = 0; > > diff --git a/drivers/mmc/host/mmc_hsq.c b/drivers/mmc/host/mmc_hsq.c > index a5e05ed0fda3..11a4c1f3a970 100644 > --- a/drivers/mmc/host/mmc_hsq.c > +++ b/drivers/mmc/host/mmc_hsq.c > @@ -227,6 +227,7 @@ static int mmc_hsq_request(struct mmc_host *mmc, struct mmc_request *mrq) > return -EBUSY; > } > > + WARN_ON_ONCE(hsq->slot[tag].mrq); > hsq->slot[tag].mrq = mrq; > > /* None of the above is even compiled for my system (I'm using arm/exynos_defconfig), so this must be something else. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
