Messages in this thread | | | Date | Wed, 22 Oct 2008 00:13:42 +0200 | From | Eric Piel <> | Subject | Re: [PATCH] LIS3LV02Dx Accelerometer driver (take 4) |
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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?
Eric
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