Re: [PATCH] i386 spinlocks should use the full 32 bits, not only 8 bits

[Eric Dumazet <dada1@cosmosbay.com>]

Linus Torvalds a écrit :
> 
> On Tue, 11 Oct 2005, Eric Dumazet wrote:
> 
>>As NR_CPUS might be > 128, and every spining CPU decrements the lock, we need
>>to use more than 8 bits for a spinlock. The current (i386/x86_64)
>>implementations have a (theorical) bug in this area.
> 
> 
> I don't think there are any x86 machines with > 128 CPU's right now.
> 
> The advantage of the byte lock is that a "movb $0" is three bytes shorter 
> than a "movl $0". And that's the unlock sequence.

1) Would you prefer to change arch/i386/Kconfig

config NR_CPUS
     int "Maximum number of CPUs (2-255)"
     range 2 255

2) The unlock sequence is not anymore inlined. It appears twice or three times 
in the kernel.

3) i386 code is often taken as the base when a port is done. For example 
x86_64 has the same problem.

Eric