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Date: Fri, 21 Feb 2014 10:37:01 +0100 (CET)
From: Jiri Kosina <jkosina@...e.cz>
To: Tejun Heo <tj@...nel.org>
cc: laijs@...fujitsu.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/9] floppy: don't use PREPARE_[DELAYED_]WORK
On Thu, 20 Feb 2014, Tejun Heo wrote:
> PREPARE_[DELAYED_]WORK() are being phased out. They have few users
> and a nasty surprise in terms of reentrancy guarantee as workqueue
> considers work items to be different if they don't have the same work
> function.
>
> floppy has been multiplexing floppy_work and fd_timer with multiple
> work functions. Introduce floppy_work_workfn() and fd_timer_workfn()
> which invoke floppy_work_fn and fd_timer_fn respectively and always
> use the two functions as the work functions and update the users to
> set floppy_work_fn and fd_timer_fn instead of overriding work
> functions using PREPARE_[DELAYED_]WORK().
>
> It would probably be best to route this with other related updates
> through the workqueue tree.
>
> Lightly tested using qemu.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
Acked-by: Jiri Kosina <jkosina@...e.cz>
Thanks.
> ---
> drivers/block/floppy.c | 42 ++++++++++++++++++++++++++++--------------
> 1 file changed, 28 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index 2023043..8f5565b 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -961,17 +961,31 @@ static void empty(void)
> {
> }
>
> -static DECLARE_WORK(floppy_work, NULL);
> +static void (*floppy_work_fn)(void);
> +
> +static void floppy_work_workfn(struct work_struct *work)
> +{
> + floppy_work_fn();
> +}
> +
> +static DECLARE_WORK(floppy_work, floppy_work_workfn);
>
> static void schedule_bh(void (*handler)(void))
> {
> WARN_ON(work_pending(&floppy_work));
>
> - PREPARE_WORK(&floppy_work, (work_func_t)handler);
> + floppy_work_fn = handler;
> queue_work(floppy_wq, &floppy_work);
> }
>
> -static DECLARE_DELAYED_WORK(fd_timer, NULL);
> +static void (*fd_timer_fn)(void) = NULL;
> +
> +static void fd_timer_workfn(struct work_struct *work)
> +{
> + fd_timer_fn();
> +}
> +
> +static DECLARE_DELAYED_WORK(fd_timer, fd_timer_workfn);
>
> static void cancel_activity(void)
> {
> @@ -982,7 +996,7 @@ static void cancel_activity(void)
>
> /* this function makes sure that the disk stays in the drive during the
> * transfer */
> -static void fd_watchdog(struct work_struct *arg)
> +static void fd_watchdog(void)
> {
> debug_dcl(DP->flags, "calling disk change from watchdog\n");
>
> @@ -993,7 +1007,7 @@ static void fd_watchdog(struct work_struct *arg)
> reset_fdc();
> } else {
> cancel_delayed_work(&fd_timer);
> - PREPARE_DELAYED_WORK(&fd_timer, fd_watchdog);
> + fd_timer_fn = fd_watchdog;
> queue_delayed_work(floppy_wq, &fd_timer, HZ / 10);
> }
> }
> @@ -1005,7 +1019,8 @@ static void main_command_interrupt(void)
> }
>
> /* waits for a delay (spinup or select) to pass */
> -static int fd_wait_for_completion(unsigned long expires, work_func_t function)
> +static int fd_wait_for_completion(unsigned long expires,
> + void (*function)(void))
> {
> if (FDCS->reset) {
> reset_fdc(); /* do the reset during sleep to win time
> @@ -1016,7 +1031,7 @@ static int fd_wait_for_completion(unsigned long expires, work_func_t function)
>
> if (time_before(jiffies, expires)) {
> cancel_delayed_work(&fd_timer);
> - PREPARE_DELAYED_WORK(&fd_timer, function);
> + fd_timer_fn = function;
> queue_delayed_work(floppy_wq, &fd_timer, expires - jiffies);
> return 1;
> }
> @@ -1334,8 +1349,7 @@ static int fdc_dtr(void)
> * Pause 5 msec to avoid trouble. (Needs to be 2 jiffies)
> */
> FDCS->dtr = raw_cmd->rate & 3;
> - return fd_wait_for_completion(jiffies + 2UL * HZ / 100,
> - (work_func_t)floppy_ready);
> + return fd_wait_for_completion(jiffies + 2UL * HZ / 100, floppy_ready);
> } /* fdc_dtr */
>
> static void tell_sector(void)
> @@ -1440,7 +1454,7 @@ static void setup_rw_floppy(void)
> int flags;
> int dflags;
> unsigned long ready_date;
> - work_func_t function;
> + void (*function)(void);
>
> flags = raw_cmd->flags;
> if (flags & (FD_RAW_READ | FD_RAW_WRITE))
> @@ -1454,9 +1468,9 @@ static void setup_rw_floppy(void)
> */
> if (time_after(ready_date, jiffies + DP->select_delay)) {
> ready_date -= DP->select_delay;
> - function = (work_func_t)floppy_start;
> + function = floppy_start;
> } else
> - function = (work_func_t)setup_rw_floppy;
> + function = setup_rw_floppy;
>
> /* wait until the floppy is spinning fast enough */
> if (fd_wait_for_completion(ready_date, function))
> @@ -1486,7 +1500,7 @@ static void setup_rw_floppy(void)
> inr = result();
> cont->interrupt();
> } else if (flags & FD_RAW_NEED_DISK)
> - fd_watchdog(NULL);
> + fd_watchdog();
> }
>
> static int blind_seek;
> @@ -1863,7 +1877,7 @@ static int start_motor(void (*function)(void))
>
> /* wait_for_completion also schedules reset if needed. */
> return fd_wait_for_completion(DRS->select_date + DP->select_delay,
> - (work_func_t)function);
> + function);
> }
>
> static void floppy_ready(void)
> --
> 1.8.5.3
>
--
Jiri Kosina
SUSE Labs
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