Messages in this thread | | | From | "Petr Vandrovec" <> | Date | Tue, 19 Jun 2001 01:36:26 MET-1 | Subject | Re: gnu asm help... |
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On 18 Jun 01 at 18:20, Timur Tabi wrote: > You want to return the variable? Try this: > > static __inline__ unsigned long atomic_inc(atomic_t *v) > { > __asm__ __volatile__( > LOCK "incl %0" > :"=m" (v->counter) > :"m" (v->counter)); > > return v->counter; > }
No. Another CPU might increment value between LOCK INCL and fetching v->counter. On ia32 architecture you are almost out of luck. You can either try building atomic_inc around CMPXCHG, using it as conditional store (but CMPXCHG is not available on i386), or you can just guard your atomic variable with spinlock - but in that case there is no reason for using atomic_t at all. Best regards, Petr Vandrovec vandrove@vc.cvut.cz
P.S.: Why you need to know that value? You can either rewrite your code with atomic_dec_and_test/atomic_inc_and_test, or you overlooked some race, or you have really strange problem. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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