spin_lock and interupts

["Leon Ljunggren" <leon.ljunggren@xxxxxxxxx>]

Hi,
I working on a driver for a embedded system running Linux 2.6.20.3 and
I'm having a bit of problem getting spin_lock to work as I'd expect it
to.

The driver reads from an AVR and before it does that one need do a
write to tell it were to read is to take place. The problem is that I
have a interupt function that will also perform such a read and if it
interupts the user induced read after i2c_write but before i2c_read it
can cause the read to happen in the wrong place.

To ensure that  this doesn't happen I'm trying to use
spin_lock_irqsave, but I'm getting rather unexpected results. First of
all it doesn't seem to disable the interupt, the interupt function is
still called and secondly it just seems to ignore the lock. Even if
avr_read has aquired lock2 and then gets interupted (which it
shouldn't since interupts should be disabled, right?) avr_interupt
will not care and still call the write/read functions instead of
blocking as expected.

Any pointers to what I might be doing wrong?

Thanks
/Leon Ljunggren

----- pseudo code ----

spinlock_t lock1 = SPIN_LOCK_UNLOCKED;
spinlock_t lock2 = SPIN_LOCK_UNLOCKED;

i2c_read()
{
   spin_lock_irqsave(&lock1, lock1_flag);
   ...
   spin_unlock_irqrestore(&lock2, lock2_flag);
}

i2c_write()
{
   spin_lock_irqsave(&lock1, lock1_flag);
   ...
   spin_unlock_irqrestore(&lock2, lock2_flag);
}


i2c_irq_read()
{
   spin_lock_irqsave(&lock1, lock1_flag);
   ...
   spin_unlock_irqrestore(&lock2, lock2_flag);
}

i2c_irq_write()
{
   spin_lock_irqsave(&lock1, lock1_flag);
   ...
   spin_unlock_irqrestore(&lock2, lock2_flag);
}

avr_read()
{
   spin_lock_irqsave(&lock2, lock2_flag);
   i2c_write();
   i2c_read();
   sping_unlock_irqrestore(&lock2,lock2_flag);
}

irqreturn_t avr_interrupt(int irq, void *p)
{
   spin_lock_irqsave(&lock2, lock2_flag);
   i2c_irq_write();
   i2c_irq_read();
   sping_unlock_irqrestore(&lock2,lock2_flag);
}

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