Thanks for the reply John.
Then, I think there is a problem with the function written below which is meant
to be atomic.
static __inline__ void change_bit(int nr, volatile void * addr)
{
__asm__ __volatile__(
"btcl %1,%0"
:"=m" (ADDR)
:"Ir" (nr));
}
Regards,
Pravin
-----Original Message-----
From: John Hubbard [mailto:[EMAIL PROTECTED]
Sent: Thursday, January 17, 2008 11:17 AM
To: Pravin Nanaware
Cc: LKML
Subject: Re: Bitops source problem
Pravin Nanaware wrote:
> Hi,
>
> I was just going through the include file in the /usr/include/asm/bitops.h
>
> The function description describes it as non-atomic but it seems it is not.
>
> static __inline__ void __change_bit(int nr, volatile void * addr)
> {
> __asm__ __volatile__(
> "btcl %1,%0"
> :"=m" (ADDR)
> :"Ir" (nr));
> }
>
> The kernel version I am using is 2.6.9-42. Is it right or am I missing
> something ?
>
> Thanks,
> Pravin
>
The bitops.h comments are correct: the btc IA-32 instruction is only
atomic if used with the lock prefix. The function above does not use the
lock prefix, so it is not atomic.
thanks,
John Hubbard
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