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Date: Tue, 2 Mar 2021 18:25:51 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Zhi Li <lznuaa@...il.com>
Cc: riteshh@...eaurora.org, asutoshd@...eaurora.org,
Ulf Hansson <ulf.hansson@...aro.org>,
linux-mmc@...r.kernel.org,
kernel list <linux-kernel@...r.kernel.org>, haibo.chen@....com
Subject: Re: [PATCH 1/1] mmc: cqhci: fix random crash when remove mmc module
On 2/03/21 5:12 pm, Zhi Li wrote:
>
>
> On Tue, Mar 2, 2021 at 1:03 AM Adrian Hunter <adrian.hunter@...el.com <mailto:adrian.hunter@...el.com>> wrote:
>
> On 1/03/21 7:21 pm, Frank Li wrote:
> > [ 6684.493350] Unable to handle kernel paging request at virtual address ffff800011c5b0f0
> > [ 6684.498531] mmc0: card 0001 removed
> > [ 6684.501556] Mem abort info:
> > [ 6684.509681] ESR = 0x96000047
> > [ 6684.512786] EC = 0x25: DABT (current EL), IL = 32 bits
> > [ 6684.518394] SET = 0, FnV = 0
> > [ 6684.521707] EA = 0, S1PTW = 0
> > [ 6684.524998] Data abort info:
> > [ 6684.528236] ISV = 0, ISS = 0x00000047
> > [ 6684.532986] CM = 0, WnR = 1
> > [ 6684.536129] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000081b22000
> > [ 6684.543923] [ffff800011c5b0f0] pgd=00000000bffff003, p4d=00000000bffff003, pud=00000000bfffe003, pmd=00000000900e1003, pte=0000000000000000
> > [ 6684.557915] Internal error: Oops: 96000047 [#1] PREEMPT SMP
> > [ 6684.564240] Modules linked in: sdhci_esdhc_imx(-) sdhci_pltfm sdhci cqhci mmc_block mmc_core fsl_jr_uio caam_jr caamkeyblob_desc caamhash_desc caamalg_desc crypto_engine rng_core authenc libdes crct10dif_ce flexcan can_dev caam error [last unloaded: mmc_core]
> > [ 6684.587281] CPU: 0 PID: 79138 Comm: kworker/0:3H Not tainted 5.10.9-01410-g3ba33182767b-dirty #10
> > [ 6684.596160] Hardware name: Freescale i.MX8DXL EVK (DT)
> > [ 6684.601320] Workqueue: kblockd blk_mq_run_work_fn
> >
> > [ 6684.606094] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
> > [ 6684.612286] pc : cqhci_request+0x148/0x4e8 [cqhci]
> > ^GMessage from syslogd@ at Thu Jan 1 01:51:24 1970 ...[ 6684.617085] lr : cqhci_request+0x314/0x4e8 [cqhci]
> > [ 6684.626734] sp : ffff80001243b9f0
> > [ 6684.630049] x29: ffff80001243b9f0 x28: ffff00002c3dd000
> > [ 6684.635367] x27: 0000000000000001 x26: 0000000000000001
> > [ 6684.640690] x25: ffff00002c451000 x24: 000000000000000f
> > [ 6684.646007] x23: ffff000017e71c80 x22: ffff00002c451000
> > [ 6684.651326] x21: ffff00002c0f3550 x20: ffff00002c0f3550
> > [ 6684.656651] x19: ffff000017d46880 x18: ffff00002cea1500
> > [ 6684.661977] x17: 0000000000000000 x16: 0000000000000000
> > [ 6684.667294] x15: 000001ee628e3ed1 x14: 0000000000000278
> > [ 6684.672610] x13: 0000000000000001 x12: 0000000000000001
> > [ 6684.677927] x11: 0000000000000000 x10: 0000000000000000
> > [ 6684.683243] x9 : 000000000000002b x8 : 0000000000001000
> > [ 6684.688560] x7 : 0000000000000010 x6 : ffff00002c0f3678
> > [ 6684.693886] x5 : 000000000000000f x4 : ffff800011c5b000
> > [ 6684.699211] x3 : 000000000002d988 x2 : 0000000000000008
> > [ 6684.704537] x1 : 00000000000000f0 x0 : 0002d9880008102f
> > [ 6684.709854] Call trace:
> > [ 6684.712313] cqhci_request+0x148/0x4e8 [cqhci]
> > [ 6684.716803] mmc_cqe_start_req+0x58/0x68 [mmc_core]
> > [ 6684.721698] mmc_blk_mq_issue_rq+0x460/0x810 [mmc_block]
> > [ 6684.727018] mmc_mq_queue_rq+0x118/0x2b0 [mmc_block]
> >
> > cqhci_request was called after cqhci_disable.
> >
> > cqhci_disable cqhci_request
> > { {
> > dmam_free_coherent(); (1) free
> > if(!cq_host->enable)
> > return
> > (2) pass check here
> > cq_host->enable = false;
> >
> > task_desc= get_desc(cq_host,tag);
> > ^^^^ crash here
> > (3) access memory which is already free
> >
> > } }
> >
> > Signed-off-by: Frank Li <Frank.Li@....com <mailto:Frank.Li@....com>>
> > ---
> > drivers/mmc/host/cqhci-core.c | 18 ++++++++++++++----
> > 1 file changed, 14 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/mmc/host/cqhci-core.c b/drivers/mmc/host/cqhci-core.c
> > index 93b0432bb601..36d292261e50 100644
> > --- a/drivers/mmc/host/cqhci-core.c
> > +++ b/drivers/mmc/host/cqhci-core.c
> > @@ -389,6 +389,7 @@ static void cqhci_off(struct mmc_host *mmc)
> > static void cqhci_disable(struct mmc_host *mmc)
> > {
> > struct cqhci_host *cq_host = mmc->cqe_private;
> > + unsigned long flags;
> >
> > if (!cq_host->enabled)
> > return;
> > @@ -397,6 +398,11 @@ static void cqhci_disable(struct mmc_host *mmc)
> >
> > __cqhci_disable(cq_host);
> >
> > + /* need wait for cqhci_request finish before free memory */
> > + spin_lock_irqsave(&cq_host->lock, flags);
> > + cq_host->enabled = false;
> > + spin_unlock_irqrestore(&cq_host->lock, flags);
> > +
> > dmam_free_coherent(mmc_dev(mmc), cq_host->data_size,
> > cq_host->trans_desc_base,
> > cq_host->trans_desc_dma_base);
> > @@ -408,7 +414,6 @@ static void cqhci_disable(struct mmc_host *mmc)
> > cq_host->trans_desc_base = NULL;
> > cq_host->desc_base = NULL;
> >
> > - cq_host->enabled = false;
> > }
> >
> > static void cqhci_prep_task_desc(struct mmc_request *mrq,
> > @@ -612,6 +617,13 @@ static int cqhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
> > cq_host->ops->enable(mmc);
> > }
> >
> > + spin_lock_irqsave(&cq_host->lock, flags);
> > + if (!cq_host->enabled) {
> > + pr_err("%s: cqhci: not enabled\n", mmc_hostname(mmc));
> > + err = -EINVAL;
> > + goto out_unlock;
> > + }
> > +
> > if (mrq->data) {
> > cqhci_prep_task_desc(mrq, cq_host, tag);
> >
> > @@ -619,14 +631,12 @@ static int cqhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
> > if (err) {
> > pr_err("%s: cqhci: failed to setup tx desc: %d\n",
> > mmc_hostname(mmc), err);
> > - return err;
> > + goto out_unlock;
> > }
> > } else {
> > cqhci_prep_dcmd_desc(mmc, mrq);
> > }
> >
> > - spin_lock_irqsave(&cq_host->lock, flags);
> > -
> > if (cq_host->recovery_halt) {
> > err = -EBUSY;
> > goto out_unlock;
> >
>
> Please try the following instead:
>
>
> diff --git a/drivers/mmc/core/bus.c b/drivers/mmc/core/bus.c
> index c2e70b757dd1..dfc8d2877115 100644
> --- a/drivers/mmc/core/bus.c
> +++ b/drivers/mmc/core/bus.c
> @@ -399,11 +399,6 @@ void mmc_remove_card(struct mmc_card *card)
> mmc_remove_card_debugfs(card);
> #endif
>
> - if (host->cqe_enabled) {
> - host->cqe_ops->cqe_disable(host);
> - host->cqe_enabled = false;
> - }
> -
> if (mmc_card_present(card)) {
> if (mmc_host_is_spi(card->host)) {
> pr_info("%s: SPI card removed\n",
> @@ -416,6 +411,11 @@ void mmc_remove_card(struct mmc_card *card)
> of_node_put(card->dev.of_node);
> }
>
> + if (host->cqe_enabled) {
> + host->cqe_ops->cqe_disable(host);
> + host->cqe_enabled = false;
> + }
> +
> put_device(&card->dev);
> }
>
>
> Actually this is my first solution, it can't resolve issues 100% and just reduce possibility.
>
> One core run The another core run
> mmc_remove_card mmc_mq_queue_rq
> { {
>
> if (mmc_card_removed(mq->card)) {
> req->rq_flags |= RQF_QUIET;
> return BLK_STS_IOERR;
> }
> //pass check here
> device_del(&card->dev);
Deleting the card device removes it from the block driver
(i.e. mmc_blk_remove()), which cleans up the request queues,
so the scenario you describe here should never happen.
Can you determine if mmc_blk_remove() is called and whether
it cleans up blk queues?
> //free resource here
> host->cqe_ops->cqe_disable(host);
>
> call cqhci_request
> //kernel dump here to access memory that is already free.
>
> } }
>
> There is one fundamental problem that there is NOT read lock when checking mmc_card_removed, and write lock for updating md->card.
> The risk conditions always exist between queue request and card remove.
>
> There are no issues for non-command queue host controllers, it just causes a redundant cmd sent by host, cmd will be timeout. Just an expected IO error
> happened. Maybe just errors code is different.
>
> But Cmd queue is different, cmd queue disabled function free memory resources. if risk conditions happen, there are kernel dump.
>
>
>
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