Hi all, I encountered a dead lock issue. Two threads try to claim host, unfortunately one thread needs to sync with the other. I encountered this issue with SD card when testing system entering S3. Does anybody encounter the same issue? Environment: 1. without CONFIG_MMC_UNSAFE_RESUME operation 2. the SD card mounted During system tried to enter S3, mmc_pm_notifier will be called first to remove SD card. So calling sequence in SD remove thread is like this: mmc_claim_host bus_ops->remove .... .... mmc_cleanup_queue kthread_stop(mq->thread) ... ... Mean while, mmc_cleanup_queue wakes up mq->thread, the calling sequence in mq->thread is like this: mmc_queue_thread mq->issue_fn (mmc_blk_issue_rq) mmc_claim_host (dead lock) .... .... Since mmc_claim_host is called in mq->thread (not SD remove thread) again, unfortunately right now host is already claimed by SD remove thread which is also waiting for mq->thread finished, so cause a dead lock here. Move the mmc_claim_host(in mmc_pm_notifier) after bus_ops->remove can resolve this dead lock. mmc_suspend_host() is using the same way to claim host. Need to know your suggestions. Signed-off-by: He Bo <bo.he@xxxxxxxxx> Signed-off-by: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx> --- drivers/mmc/core/core.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 68091dd..1e27588 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -1850,11 +1850,10 @@ int mmc_pm_notify(struct notifier_block *notify_block, if (!host->bus_ops || host->bus_ops->suspend) break; - mmc_claim_host(host); - if (host->bus_ops->remove) host->bus_ops->remove(host); + mmc_claim_host(host); mmc_detach_bus(host); mmc_release_host(host); host->pm_flags = 0; -- 1.7.3.4 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
