Messages in this thread | | | Date | Tue, 21 Oct 2008 15:21:42 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] LIS3LV02Dx Accelerometer driver (take 4) |
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On Wed, 22 Oct 2008 00:13:42 +0200 Eric Piel <eric.piel@tremplin-utc.net> wrote:
> Andrew Morton schreef: > >> +static void lis3lv02d_poweroff_timeout(unsigned long data) > >> +{ > >> + struct acpi_lis3lv02d *dev = (void *)data; > >> + > >> + up(&dev->poff_sem); > >> + lis3lv02d_poweroff(dev->device->handle); > >> + down(&dev->poff_sem); > > > > eek, no, we cannot down a semaphore from a timer handler! It will lead > > to might_sleep() warnings, scheduling-in-atomic warnings and kernel > > deadlocks. > Ooh... What happened is that I wrote the other functions first. They > indirectly use acpi_evaluate_integer(), which can sleep. So I avoided > spin_locks, and decided to use a semaphore. But now there is a semaphore > in a timer (which is not allowed to sleep). > > It seems the semaphore usage is compulsory due to acpi, so I'm planning > to change the timer into a scheduled work on a workqueue (with > queue_delayed_work(), and cancel_delayed_work_sync()). This workqueue > could be the same as the one for the joystick input. Does that look the > right way to do it?
yep, that's generally a safe transformation.
You might also be able to use keventd, via scheule_delayed_work().
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