Linux Driver Verification » Linux Kernel Safety RuleDB

The second example:
[SCSI] target: Fix interrupt context bug with stats_lock and core_tmr_alloc_req
http://git.kernel.org/?p=linux/kernel/git/stable/linux-stable.git;a=commitdiff;h=1e7de68c57daf75ec4b721f101f88cccf029e38c

spin_unlock_irq() cannot be called in IRQ context

But the patch in the second example enables call to spin_unlock_irq

-       spin_unlock(&dev->stats_lock);
+       spin_unlock_irq(&dev->stats_lock);

Example:
https://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=b59f6d1febd6cbe9fae4589bf72da0ed32bc69e0

commits from linux-stable repository (with class specific:context:interrupt:enable_irq)
3e3742b
c690d5d

After careful reading "The Spinlock Functions" section of 5th LDD3 chapter I guess that there is another problem actually. Being in interrupt context one should use spin locking that disables interrupts. Otherwise sooner or later the system may catch a deadlock. That is why Vadim has properly noticed that spin_[un]lock was changed with spin_[un]lock_irq in interrupt context:
Vadim Mutilin wrote:

[...]

But the patch in the second example enables call to spin_unlock_irq
[...]

The problem considered in description comes from sequence:

 spin_unlock_irq(&a);
 spin_lock_irqsave(&b);
 spin_unlock_irqsave(&b);
 spin_lock_irq(&a);

Another problem, e.g. as considered in example provided by Denis, is in spin_lock_irq vs spin_lock_irqsave usage. It's also considered in "The Spinlock Functions" section. Here you can find an example of bad things. BTW eventually spin_[un]lock_irq used in this commit was changed with spin_lock_irqsave/spin_unlock_irqrestore.