On 4/13/22 19:12, Ulf Hansson wrote:
On Wed, 13 Apr 2022 at 10:07, Rokudo Yan <wu-yan@xxxxxxx> wrote:There is a potential livelock when mmc_sd_detect is invoked by pm_suspend, as below: [thread do suspend] state_store -pm_suspend -__pm_notifier_call_chain -mmc_pm_notify -cancel_delayed_work_sync(&host->detect) -__cancel_work_timer -__flush_work -wait_for_completion wait for detect work current running to complete [kworker run detect work] process_one_work -mmc_rescan -mmc_sd_detect -mmc_get_card -__mmc_claim_host -schedule wait for current host claimer release [kworker dispatch io (current host claimer)] process_one_work -blk_mq_run_work_fn -__blk_mq_run_hw_queue -blk_mq_sched_dispatch_requests -blk_mq_do_dispatch_sched -blk_mq_dispatch_rq_list -mmc_mq_queue_rq -mmc_get_card -- claim mmc host if inflight=1 (the first io) and only release when all ios complete -mmc_blk_mq_issue_rq if there are continous io requests in the system to keep queue busy (inflight !=0 all the time), the supsend process will blocked and hang the system. This issue can reproduced by steps below: 1. prepare 1 SD card 2. run fio to keep the card io busy fio --size=1m --bs=32k --ioengine=libaio --iodepth=64 \ --direct=1 --rw=read --time_based --runtime=60000 \ --name=test --filename=<path under sd card> 3. suspend the system (echo mem > /sys/power/state) 4. resume the system 5. suspend the system again & device hang Signed-off-by: Rokudo Yan <wu-yan@xxxxxxx>I believe you are running some vendor/old kernel, because I think this problem has been fixed. You may have a look at commit 17a17bf50612 ("mmc: core: Fix hanging on I/O during system suspend for removable cards") Kind regards Uffe--- drivers/mmc/core/queue.c | 8 ++++++++ drivers/mmc/core/sd.c | 2 ++ include/linux/mmc/host.h | 3 +++ 3 files changed, 13 insertions(+) diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c index c69b2d9df6f1..f00fc45a4fd5 100644 --- a/drivers/mmc/core/queue.c +++ b/drivers/mmc/core/queue.c @@ -241,6 +241,14 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx, return BLK_STS_IOERR; } + /* + * requeue the io if sd detect is on-going to avoid livelock + * when mmc_sd_detect is invoked by pm_suspend and there are + * continous io requests simultaneously. + */ + if (host->doing_sd_detect) + return BLK_STS_RESOURCE; + issue_type = mmc_issue_type(mq, req); spin_lock_irq(&mq->lock); diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c index 68df6b2f49cc..460ea6ab9aba 100644 --- a/drivers/mmc/core/sd.c +++ b/drivers/mmc/core/sd.c @@ -1594,6 +1594,7 @@ static void mmc_sd_detect(struct mmc_host *host) { int err; + host->doing_sd_detect = true; mmc_get_card(host->card, NULL); /* @@ -1611,6 +1612,7 @@ static void mmc_sd_detect(struct mmc_host *host) mmc_power_off(host); mmc_release_host(host); } + host->doing_sd_detect = false; } static int sd_can_poweroff_notify(struct mmc_card *card) diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index 7afb57cab00b..4abfc5d7ef20 100644 --- a/include/linux/mmc/host.h +++ b/include/linux/mmc/host.h @@ -501,6 +501,9 @@ struct mmc_host { /* Host Software Queue support */ bool hsq_enabled; + /* indicate SD detect on-going */ + bool doing_sd_detect; + unsigned long private[] ____cacheline_aligned; }; -- 2.25.1
Hi, Uffe Thanks for reply, the kernel version used in our device is kernel-4.19 And the patch you mentioned is not applied, I will try to apply the patch. Thanks yanwu
