On 14 June 2015 at 19:26, Rabin Vincent <rabin.vincent@xxxxxxxx> wrote:
> On systems with CONFIG_PREEMPT=n, under certain circumstances, mmcqd
> can continuously process requests for several seconds without blocking,
> triggering the soft lockup watchdog. For example, this can happen if
> mmcqd runs on the CPU which services the controller's interrupt, and
> a process on a different CPU continuously writes to the MMC block
> device.
>
> NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [mmcqd/0:664]
> CPU: 0 PID: 664 Comm: mmcqd/0 Not tainted 4.1.0-rc7+ #4
> PC is at _raw_spin_unlock_irqrestore+0x24/0x28
> LR is at mmc_start_request+0x104/0x134
> ...
> [<805112a8>] (_raw_spin_unlock_irqrestore) from [<803db664>] (mmc_start_request+0x104/0x134)
> [<803db664>] (mmc_start_request) from [<803dc008>] (mmc_start_req+0x274/0x394)
> [<803dc008>] (mmc_start_req) from [<803eb2c4>] (mmc_blk_issue_rw_rq+0xd0/0xb98)
> [<803eb2c4>] (mmc_blk_issue_rw_rq) from [<803ebe8c>] (mmc_blk_issue_rq+0x100/0x470)
> [<803ebe8c>] (mmc_blk_issue_rq) from [<803ecab8>] (mmc_queue_thread+0xd0/0x170)
> [<803ecab8>] (mmc_queue_thread) from [<8003fd14>] (kthread+0xe0/0xfc)
> [<8003fd14>] (kthread) from [<8000f768>] (ret_from_fork+0x14/0x2c)
>
> Fix it by adding a cond_resched() in the request handling loop so that
> other processes get a chance to run.
>
> Signed-off-by: Rabin Vincent <rabin.vincent@xxxxxxxx>
Thanks, applied!
Kind regards
Uffe
> ---
> drivers/mmc/card/queue.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
> index 8efa368..e78ae97 100644
> --- a/drivers/mmc/card/queue.c
> +++ b/drivers/mmc/card/queue.c
> @@ -69,6 +69,7 @@ static int mmc_queue_thread(void *d)
> set_current_state(TASK_RUNNING);
> cmd_flags = req ? req->cmd_flags : 0;
> mq->issue_fn(mq, req);
> + cond_resched();
> if (mq->flags & MMC_QUEUE_NEW_REQUEST) {
> mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
> continue; /* fetch again */
> --
> 1.7.10.4
>
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