Re: [PATCH 3/3] scsi: 3w-9xxx: rework lock timeouts

adam radford
2017-11-10T19:36:53Z

On Fri, Nov 10, 2017 at 7:58 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> The TW_IOCTL_GET_LOCK ioctl uses do_gettimeofday() to check whether
> a lock has expired. This can misbehave due to a concurrent
> settimeofday() call, as it is based on 'real' time, and it
> will overflow in y2038 on 32-bit architectures, producing
> unexpected results when used across the overflow time.
>
> This changes it to using monotonic time, using ktime_get()
> to simplify the code.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/scsi/3w-9xxx.c | 13 ++++++-------
> drivers/scsi/3w-9xxx.h | 2 +-
> 2 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/scsi/3w-9xxx.c b/drivers/scsi/3w-9xxx.c
> index b1c9bd9c1bfd..b42c9c479d4b 100644
> --- a/drivers/scsi/3w-9xxx.c
> +++ b/drivers/scsi/3w-9xxx.c
> @@ -645,8 +645,7 @@ static long twa_chrdev_ioctl(struct file *file, unsigned int cmd, unsigned long
> TW_Command_Full *full_command_packet;
> TW_Compatibility_Info *tw_compat_info;
> TW_Event *event;
> - struct timeval current_time;
> - u32 current_time_ms;
> + ktime_t current_time;
> TW_Device_Extension *tw_dev = twa_device_extension_list[iminor(inode)];
> int retval = TW_IOCTL_ERROR_OS_EFAULT;
> void __user *argp = (void __user *)arg;
> @@ -837,17 +836,17 @@ static long twa_chrdev_ioctl(struct file *file, unsigned int cmd, unsigned long
> break;
> case TW_IOCTL_GET_LOCK:
> tw_lock = (TW_Lock *)tw_ioctl->data_buffer;
> - do_gettimeofday(&current_time);
> - current_time_ms = (current_time.tv_sec * 1000) + (current_time.tv_usec / 1000);
> + current_time = ktime_get();
>
> - if ((tw_lock->force_flag == 1) || (tw_dev->ioctl_sem_lock == 0) || (current_time_ms >= tw_dev->ioctl_msec)) {
> + if ((tw_lock->force_flag == 1) || (tw_dev->ioctl_sem_lock == 0) ||
> + ktime_after(current_time, tw_dev->ioctl_time)) {
> tw_dev->ioctl_sem_lock = 1;
> - tw_dev->ioctl_msec = current_time_ms + tw_lock->timeout_msec;
> + tw_dev->ioctl_time = ktime_add_ms(current_time, tw_lock->timeout_msec);
> tw_ioctl->driver_command.status = 0;
> tw_lock->time_remaining_msec = tw_lock->timeout_msec;
> } else {
> tw_ioctl->driver_command.status = TW_IOCTL_ERROR_STATUS_LOCKED;
> - tw_lock->time_remaining_msec = tw_dev->ioctl_msec - current_time_ms;
> + tw_lock->time_remaining_msec = ktime_ms_delta(tw_dev->ioctl_time, current_time);
> }
> break;
> case TW_IOCTL_RELEASE_LOCK:
> diff --git a/drivers/scsi/3w-9xxx.h b/drivers/scsi/3w-9xxx.h
> index b6c208cc474f..d88cd3499bd5 100644
> --- a/drivers/scsi/3w-9xxx.h
> +++ b/drivers/scsi/3w-9xxx.h
> @@ -666,7 +666,7 @@ typedef struct TAG_TW_Device_Extension {
> unsigned char event_queue_wrapped;
> unsigned int error_sequence_id;
> int ioctl_sem_lock;
> - u32 ioctl_msec;
> + ktime_t ioctl_time;
> int chrdev_request_id;
> wait_queue_head_t ioctl_wqueue;
> struct mutex ioctl_lock;
> --
> 2.9.0
>

Looks good... Thanks for this fix!

Acked-by: Adam Radford <aradford@gmail.com>