On Sat, 18 Aug 2007, Satyam Sharma wrote: > > No code does (or would do, or should do): > > x.counter++; > > on an "atomic_t x;" anyway. That's just an example of a general problem. No, you don't use "x.counter++". But you *do* use if (atomic_read(&x) <= 1) and loading into a register is stupid and pointless, when you could just do it as a regular memory-operand to the cmp instruction. And as far as the compiler is concerned, the problem is the 100% same: combining operations with the volatile memop. The fact is, a compiler that thinks that movl mem,reg cmpl $val,reg is any better than cmpl $val,mem is just not a very good compiler. But when talking about "volatile", that's exactly what ytou always get (and always have gotten - this is not a regression, and I doubt gcc is alone in this). Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
- Follow-Ups:
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Denys Vlasenko <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: "Paul E. McKenney" <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Satyam Sharma <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- References:
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Herbert Xu <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Segher Boessenkool <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Nick Piggin <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Segher Boessenkool <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Nick Piggin <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Paul Mackerras <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Nick Piggin <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Linus Torvalds <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: "Paul E. McKenney" <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Herbert Xu <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: "Paul E. McKenney" <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Christoph Lameter <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- From: Satyam Sharma <[email protected]>
- Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- Prev by Date: Re: [PATCH] rtc: Make rtc-ds1742 driver hotplug-aware
- Next by Date: [PATCH 1/2] scripts/get_maintainer.pl
- Previous by thread: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- Next by thread: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
- Index(es):