From df3ef2d3c92c0a562ebde3699af7d12401fddf60 Mon Sep 17 00:00:00 2001 From: Guennadi Liakhovetski Date: Thu, 21 Apr 2011 07:20:16 +0000 Subject: [PATCH] mmc: protect the tmio_mmc driver against a theoretical race The MMC subsystem does not guarantee, that host driver .request() and .set_ios() callbacks are serialised. Such concurrent calls, however, do not have to be meaningfully supported, drivers just have to make sure to avoid any severe problems. Signed-off-by: Guennadi Liakhovetski Signed-off-by: Chris Ball --- drivers/mmc/host/tmio_mmc.h | 1 + drivers/mmc/host/tmio_mmc_pio.c | 62 +++++++++++++++++++++++++++++++++++++---- 2 files changed, 57 insertions(+), 6 deletions(-) diff --git a/drivers/mmc/host/tmio_mmc.h b/drivers/mmc/host/tmio_mmc.h index c1470e6b138d..58138a203877 100644 --- a/drivers/mmc/host/tmio_mmc.h +++ b/drivers/mmc/host/tmio_mmc.h @@ -19,6 +19,7 @@ #include #include #include +#include /* Definitions for values the CTRL_SDIO_STATUS register can take. */ #define TMIO_SDIO_STAT_IOIRQ 0x0001 diff --git a/drivers/mmc/host/tmio_mmc_pio.c b/drivers/mmc/host/tmio_mmc_pio.c index 8b05d3ceb29c..ea6ade31bcc7 100644 --- a/drivers/mmc/host/tmio_mmc_pio.c +++ b/drivers/mmc/host/tmio_mmc_pio.c @@ -244,8 +244,12 @@ static void tmio_mmc_reset_work(struct work_struct *work) spin_lock_irqsave(&host->lock, flags); mrq = host->mrq; - /* request already finished */ - if (!mrq + /* + * is request already finished? Since we use a non-blocking + * cancel_delayed_work(), it can happen, that a .set_ios() call preempts + * us, so, have to check for IS_ERR(host->mrq) + */ + if (IS_ERR_OR_NULL(mrq) || time_is_after_jiffies(host->last_req_ts + msecs_to_jiffies(2000))) { spin_unlock_irqrestore(&host->lock, flags); @@ -265,16 +269,19 @@ static void tmio_mmc_reset_work(struct work_struct *work) host->cmd = NULL; host->data = NULL; - host->mrq = NULL; host->force_pio = false; spin_unlock_irqrestore(&host->lock, flags); tmio_mmc_reset(host); + /* Ready for new calls */ + host->mrq = NULL; + mmc_request_done(host->mmc, mrq); } +/* called with host->lock held, interrupts disabled */ static void tmio_mmc_finish_request(struct tmio_mmc_host *host) { struct mmc_request *mrq = host->mrq; @@ -282,13 +289,15 @@ static void tmio_mmc_finish_request(struct tmio_mmc_host *host) if (!mrq) return; - host->mrq = NULL; host->cmd = NULL; host->data = NULL; host->force_pio = false; cancel_delayed_work(&host->delayed_reset_work); + host->mrq = NULL; + + /* FIXME: mmc_request_done() can schedule! */ mmc_request_done(host->mmc, mrq); } @@ -686,15 +695,27 @@ static int tmio_mmc_start_data(struct tmio_mmc_host *host, static void tmio_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq) { struct tmio_mmc_host *host = mmc_priv(mmc); + unsigned long flags; int ret; - if (host->mrq) + spin_lock_irqsave(&host->lock, flags); + + if (host->mrq) { pr_debug("request not null\n"); + if (IS_ERR(host->mrq)) { + spin_unlock_irqrestore(&host->lock, flags); + mrq->cmd->error = -EAGAIN; + mmc_request_done(mmc, mrq); + return; + } + } host->last_req_ts = jiffies; wmb(); host->mrq = mrq; + spin_unlock_irqrestore(&host->lock, flags); + if (mrq->data) { ret = tmio_mmc_start_data(host, mrq->data); if (ret) @@ -709,8 +730,8 @@ static void tmio_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq) } fail: - host->mrq = NULL; host->force_pio = false; + host->mrq = NULL; mrq->cmd->error = ret; mmc_request_done(mmc, mrq); } @@ -724,6 +745,29 @@ fail: static void tmio_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) { struct tmio_mmc_host *host = mmc_priv(mmc); + unsigned long flags; + + spin_lock_irqsave(&host->lock, flags); + if (host->mrq) { + if (IS_ERR(host->mrq)) { + dev_dbg(&host->pdev->dev, + "%s.%d: concurrent .set_ios(), clk %u, mode %u\n", + current->comm, task_pid_nr(current), + ios->clock, ios->power_mode); + host->mrq = ERR_PTR(-EINTR); + } else { + dev_dbg(&host->pdev->dev, + "%s.%d: CMD%u active since %lu, now %lu!\n", + current->comm, task_pid_nr(current), + host->mrq->cmd->opcode, host->last_req_ts, jiffies); + } + spin_unlock_irqrestore(&host->lock, flags); + return; + } + + host->mrq = ERR_PTR(-EBUSY); + + spin_unlock_irqrestore(&host->lock, flags); if (ios->clock) tmio_mmc_set_clock(host, ios->clock); @@ -754,6 +798,12 @@ static void tmio_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) /* Let things settle. delay taken from winCE driver */ udelay(140); + if (PTR_ERR(host->mrq) == -EINTR) + dev_dbg(&host->pdev->dev, + "%s.%d: IOS interrupted: clk %u, mode %u", + current->comm, task_pid_nr(current), + ios->clock, ios->power_mode); + host->mrq = NULL; } static int tmio_mmc_get_ro(struct mmc_host *mmc) -- 2.11.0