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Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to tri
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy |
Date: |
Tue, 31 Mar 2015 13:23:05 +1100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Mon, Mar 30, 2015 at 10:17:06AM +0200, Paolo Bonzini wrote:
>
>
> On 19/03/2015 10:33, Dr. David Alan Gilbert wrote:
> >> > But still pointless. Atomicity isn't magic pixie dust; it only makes
> >> > sense if you're making atomic specific operations that need to be.
> >> > Simple integer loads and stores are already atomic. Unless at least
> >> > some of the atomic operations are something more complex, there's
> >> > really no point to atomically marked operations.
> > OK, I'll kill it off.
>
> No, don't.
>
> And both of you, read docs/atomics.txt.
*reads*
> "atomic_read() and atomic_set() prevents the compiler from using
> optimizations that might otherwise optimize accesses out of existence
> on the one hand, or that might create unsolicited accesses on the other.
> [...] it tells readers which variables are shared with
> other threads, and which are local to the current thread or protected
> by other, more mundane means."
>
> atomic_read() and atomic_set() provide the same guarantees as
> ACCESS_ONCE in the Linux kernel.
Ok, having better understood the semantics and intentions of the
atomic_* functions in qemu, I withdraw my objection. They do seem
like the right primitives for this situation.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, (continued)
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Dr. David Alan Gilbert, 2015/03/13
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, David Gibson, 2015/03/16
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Dr. David Alan Gilbert, 2015/03/18
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, David Gibson, 2015/03/19
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Dr. David Alan Gilbert, 2015/03/19
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, David Gibson, 2015/03/22
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Paolo Bonzini, 2015/03/30
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Dr. David Alan Gilbert, 2015/03/30
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Paolo Bonzini, 2015/03/30
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Paolo Bonzini, 2015/03/30
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy,
David Gibson <=