Re: Could this become a race condition?
Alan Cox (alan@lxorguk.ukuu.org.uk)
Wed, 16 Oct 1996 23:02:12 +0100 (BST)
> extern inline void lock_super(struct super_block * sb)
> {
> if (sb->s_lock)
> __wait_on_super(sb);
> sb->s_lock = 1;
> }
>
> What happen if two execution threads (particurlarly on a SMP machine)
> check the value of the variable sb->s_lock _at the same time_, and see
> that the value is zero? Both the 2 threads will set this variable to 1,
> and consider that they have the lock on the super_block ?
Kernel threads of code are only pre-empted by interrupts so its safe except
from an interrupt. The SMP kernel only allows one processor in kernel space
at a time so it doesnt arise either.
In future when we take the giant leap and set the kernel up for finer
grained SMP locking your comment will become true.
Alan