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From
SubjectRe: deadlock avoidance?
Date
Tuesday, December 07, 1999 11:56 PM
Johannes Erdfelt <jerdfelt@sventech.com> wrote :
> > AFAIK spin_lock_irq() does not permit IRQ firing.
>
> On that CPU, look at the SMP case.
>
> JE
>

spin_lock_irqsave() guaranteed that only an uninterrupted CPU execute the
code protected by the lock.
See at this implementation ( optimization = 0.0 ) :

struct s_nested_lock {
spinlock_t lock;
short int pid;
short int count;
};


#define nested_lock(lock, flags) \
if (lock->pid == getpid()) { \
++lock->count; \
} else { \
spin_lock_irqsave(&lock->lock, flags); \
lock->pid = getpid(); \
}

#define nested_unlock(lock, flags) \
if (--lock->count == 0) { \
lock->pid = 0; \
spin_unlock_irqrestore(&lock->lock, flags); \
}


Cheers,
Davide.

--
"Debian, the Freedom in Freedom."



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