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SubjectRe: inconsistent usage of
On Tue, Apr 22 2003, wrote:
> I found inconsistent behavoir between SMP oand none SMP kernels using spin
> locks inside driver programming
> As first an simple example:
> static spinlock_t qtlock = SPIN_LOCK_UNLOCKED;
> void foo()
> {
> unsigned long local_flags;
> spin_lock_irqsave (&qtlock, local_flags);
> spin_lock_irqsave (&qtlock, local_flags);
> }

[snip rant]

Check the spinlock implementation. All the above does in UP is
disable/save interrupts twice. The actual spinlock is a nop. As only one
processor can be executing inside the kernel in UP, you only need to
guard against interrupts.

Jens Axboe

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