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Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to tri
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy |
Date: |
Tue, 31 Mar 2015 12:21:10 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
* Paolo Bonzini (address@hidden) wrote:
>
>
> On 30/03/2015 19:04, Dr. David Alan Gilbert wrote:
> >>> > > That one's a trickier question. Compilers are absolutely capable
> >>> > > of optimizing that far, *but* the C rules about when it's allowed
> >>> > > to assume in-memory values remain unchanged are pretty
> >>> > > conservative. I think any function call in the loop will require
> >>> > > it to reload the value, for example. That said, a (compiler only)
> >>> > > memory barrier might be appropriate to ensure that reload.
> >> >
> >> > That's exactly what atomic_read provides.
> > So does that say I need the atomic_read but not the atomic_write -
> > which seems a bit weird, but I think only due to the naming.
>
> No, you need both even though it's even more far-fetched that the
> compiler will do something bad with the set.
OK, done - it's back to where it was with atomic_set/atomic_read.
Dave
>
> Paolo
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, David Gibson, 2015/03/13
- 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,
Dr. David Alan Gilbert <=
- 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, 2015/03/30