[PATCH linux dev-4.10] drivers: fsi: SBEFIFO: switch to workqueue instead of timer
Joel Stanley
joel at jms.id.au
Wed Dec 20 13:57:10 AEDT 2017
On Tue, Dec 19, 2017 at 6:43 AM, Eddie James <eajames at linux.vnet.ibm.com> wrote:
> From: "Edward A. James" <eajames at us.ibm.com>
>
> Some systems are experiencing scheduling problems; mod_timer can take up
> to several seconds before the timer_function is executed, even if passed
> the current jiffies.
How did you work out that the timer wasn't firing?
Can you describe the other tests you have done?
It's not recommended to paper over something going wrong by changing
over to a workqueue.
Cheers,
Joel
>
> Work around this by using sbefifo's own workqueue.
>
> Signed-off-by: Edward A. James <eajames at us.ibm.com>
> ---
> drivers/fsi/fsi-sbefifo.c | 54 ++++++++++++++++++++++++++++-------------------
> 1 file changed, 32 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
> index 0697a10..7b6842a 100644
> --- a/drivers/fsi/fsi-sbefifo.c
> +++ b/drivers/fsi/fsi-sbefifo.c
> @@ -29,9 +29,9 @@
> #include <linux/sched.h>
> #include <linux/slab.h>
> #include <linux/spinlock.h>
> -#include <linux/timer.h>
> #include <linux/uaccess.h>
> #include <linux/wait.h>
> +#include <linux/workqueue.h>
>
> /*
> * The SBEFIFO is a pipe-like FSI device for communicating with
> @@ -57,7 +57,7 @@
> #define SBEFIFO_MAX_RESCHDULE msecs_to_jiffies(5000)
>
> struct sbefifo {
> - struct timer_list poll_timer;
> + struct delayed_work work;
> struct fsi_device *fsi_dev;
> struct miscdevice mdev;
> wait_queue_head_t wait;
> @@ -99,6 +99,8 @@ struct sbefifo_client {
> unsigned long f_flags;
> };
>
> +static struct workqueue_struct *sbefifo_wq;
> +
> static DEFINE_IDA(sbefifo_ida);
>
> static int sbefifo_inw(struct sbefifo *sbefifo, int reg, u32 *word)
> @@ -337,7 +339,7 @@ static void sbefifo_client_release(struct kref *kref)
> */
> set_bit(SBEFIFO_XFR_CANCEL, &xfr->flags);
> sbefifo_get(sbefifo);
> - if (mod_timer(&client->dev->poll_timer, jiffies))
> + if (!queue_work(sbefifo_wq, &sbefifo->work.work))
> sbefifo_put(sbefifo);
> }
> }
> @@ -374,10 +376,11 @@ static struct sbefifo_xfr *sbefifo_next_xfr(struct sbefifo *sbefifo)
> return NULL;
> }
>
> -static void sbefifo_poll_timer(unsigned long data)
> +static void sbefifo_worker(struct work_struct *work)
> {
> static const unsigned long EOT_MASK = 0x000000ff;
> - struct sbefifo *sbefifo = (void *)data;
> + struct delayed_work *dwork = to_delayed_work(work);
> + struct sbefifo *sbefifo = container_of(dwork, struct sbefifo, work);
> struct sbefifo_buf *rbuf, *wbuf;
> struct sbefifo_xfr *xfr, *tmp;
> struct sbefifo_buf drain;
> @@ -393,6 +396,7 @@ static void sbefifo_poll_timer(unsigned long data)
> if (!xfr)
> goto out_unlock;
>
> +again:
> rbuf = xfr->rbuf;
> wbuf = xfr->wbuf;
>
> @@ -414,9 +418,8 @@ static void sbefifo_poll_timer(unsigned long data)
> devn = sbefifo_dev_nwwriteable(sts);
> if (devn == 0) {
> /* No open slot for write. Reschedule. */
> - sbefifo->poll_timer.expires = jiffies +
> - SBEFIFO_RESCHEDULE;
> - add_timer(&sbefifo->poll_timer);
> + queue_delayed_work(sbefifo_wq, &sbefifo->work,
> + SBEFIFO_RESCHEDULE);
> goto out_unlock;
> }
>
> @@ -468,9 +471,8 @@ static void sbefifo_poll_timer(unsigned long data)
> }
>
> /* No data yet. Reschedule. */
> - sbefifo->poll_timer.expires = jiffies +
> - SBEFIFO_RESCHEDULE;
> - add_timer(&sbefifo->poll_timer);
> + queue_delayed_work(sbefifo_wq, &sbefifo->work,
> + SBEFIFO_RESCHEDULE);
> goto out_unlock;
> } else {
> xfr->wait_data_timeout = 0;
> @@ -516,10 +518,12 @@ static void sbefifo_poll_timer(unsigned long data)
> }
> INIT_LIST_HEAD(&sbefifo->xfrs);
>
> - } else if (eot && sbefifo_next_xfr(sbefifo)) {
> - sbefifo_get(sbefifo);
> - sbefifo->poll_timer.expires = jiffies;
> - add_timer(&sbefifo->poll_timer);
> + } else if (eot) {
> + xfr = sbefifo_next_xfr(sbefifo);
> + if (xfr) {
> + wake_up_interruptible(&sbefifo->wait);
> + goto again;
> + }
> }
>
> sbefifo_put(sbefifo);
> @@ -638,7 +642,7 @@ static ssize_t sbefifo_read_common(struct sbefifo_client *client,
> * Fill the read buffer back up.
> */
> sbefifo_get(sbefifo);
> - if (mod_timer(&client->dev->poll_timer, jiffies))
> + if (!queue_work(sbefifo_wq, &sbefifo->work.work))
> sbefifo_put(sbefifo);
> } else {
> list_del(&xfr->client);
> @@ -721,7 +725,7 @@ static ssize_t sbefifo_write_common(struct sbefifo_client *client,
> &n))) {
> set_bit(SBEFIFO_XFR_CANCEL, &xfr->flags);
> sbefifo_get(sbefifo);
> - if (mod_timer(&sbefifo->poll_timer, jiffies))
> + if (!queue_work(sbefifo_wq, &sbefifo->work.work))
> sbefifo_put(sbefifo);
>
> ret = -ERESTARTSYS;
> @@ -741,7 +745,8 @@ static ssize_t sbefifo_write_common(struct sbefifo_client *client,
> n)) {
> set_bit(SBEFIFO_XFR_CANCEL, &xfr->flags);
> sbefifo_get(sbefifo);
> - if (mod_timer(&sbefifo->poll_timer, jiffies))
> + if (!queue_work(sbefifo_wq,
> + &sbefifo->work.work))
> sbefifo_put(sbefifo);
> ret = -EFAULT;
> goto out;
> @@ -768,7 +773,7 @@ static ssize_t sbefifo_write_common(struct sbefifo_client *client,
> * Drain the write buffer.
> */
> sbefifo_get(sbefifo);
> - if (mod_timer(&client->dev->poll_timer, jiffies))
> + if (!queue_work(sbefifo_wq, &sbefifo->work.work))
> sbefifo_put(sbefifo);
> }
>
> @@ -928,8 +933,7 @@ static int sbefifo_probe(struct device *dev)
> sbefifo->idx);
>
> /* This bit of silicon doesn't offer any interrupts... */
> - setup_timer(&sbefifo->poll_timer, sbefifo_poll_timer,
> - (unsigned long)sbefifo);
> + INIT_DELAYED_WORK(&sbefifo->work, sbefifo_worker);
>
> sbefifo->mdev.minor = MISC_DYNAMIC_MINOR;
> sbefifo->mdev.fops = &sbefifo_fops;
> @@ -982,7 +986,7 @@ static int sbefifo_remove(struct device *dev)
>
> ida_simple_remove(&sbefifo_ida, sbefifo->idx);
>
> - if (del_timer_sync(&sbefifo->poll_timer))
> + if (cancel_delayed_work_sync(&sbefifo->work))
> sbefifo_put(sbefifo);
>
> sbefifo_put(sbefifo);
> @@ -1010,11 +1014,17 @@ static int sbefifo_remove(struct device *dev)
>
> static int sbefifo_init(void)
> {
> + sbefifo_wq = create_singlethread_workqueue("sbefifo");
> + if (!sbefifo_wq)
> + return -ENOMEM;
> +
> return fsi_driver_register(&sbefifo_drv);
> }
>
> static void sbefifo_exit(void)
> {
> + destroy_workqueue(sbefifo_wq);
> +
> fsi_driver_unregister(&sbefifo_drv);
>
> ida_destroy(&sbefifo_ida);
> --
> 1.8.3.1
>
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