Nested spin_lock_irqsave

Question

If the code is as below

void test(void)
{
  spin_lock_irqsave(&lock1, flag);
  ...
  func1();
  ...
  spin_unlock_irqrestore(&lock1, flag);
}

void func1(void)
{
  spin_lock_irqsave(&lock2, flag);
  ...
  spin_unlock_irqrestore(&lock2, flag);
}

Will there be any issue with the code? when the spin_unlock_irqrestore is called in func1, will the interrupt be enabled already? What I want to achieve is test() routine can be executed without any interruption by scheduler or interrupts. Thanks a lot

Answer 1

As far as I've found in the documentation, and I haven't completely exhausted my search, the flag will save the state of the bits that set the different flags and then turn off interrupts, then restore it on end. If interrupts have been turned off by the first call test and then you do another call, I would assume (and nothing indicates otherwise that I've found) that it would leave the interrupts turned off, store the flags and restore them inside func() and then restore them back to the state flag has in test.

Interrupts should only be re-enabled after your test function.

I would say your only catch is that you cannot use the same flag variable in both functions, else you'll overwrite the first one in your inner call and then reset it, and if any flags changed in between your calls, you may reset the outer one to the wrong state.