Bug 132800

Summary: Clean up CrossThreadTask
Product: WebKit Reporter: Zan Dobersek <zan>
Component: New BugsAssignee: Zan Dobersek <zan>
Status: RESOLVED FIXED    
Severity: Normal CC: darin
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
Bug Depends on: 132798, 132799    
Bug Blocks:    
Attachments:
Description Flags
Patch
none
Patch none

Zan Dobersek
Reported 2014-05-10 23:28:15 PDT
Clean up CrossThreadTask
Attachments
Patch (58.48 KB, patch)
2014-05-10 23:36 PDT, Zan Dobersek 		no flags
DetailsFormatted DiffDiff
Patch (58.43 KB, patch)
2014-05-12 03:32 PDT, Zan Dobersek 		no flags
DetailsFormatted DiffDiff
Show Obsolete (1) View All Add attachment proposed patch, testcase, etc.
Zan Dobersek
Comment 1 2014-05-10 23:36:30 PDT
Created attachment 231253 [details] Patch
Darin Adler
Comment 2 2014-05-11 11:12:32 PDT
Comment on attachment 231253 [details] Patch This is a fine simplification, but I think we should go even further. I don’t think we want to use CrossThreadCopier. Instead we should have lambdas for each of these and copy the arguments explicitly at the call site. Need a new patch that compiles, though. EWS shows this failing to compile on most platforms.
Zan Dobersek
Comment 3 2014-05-11 14:00:39 PDT
(In reply to comment #2) > (From update of attachment 231253 [details]) > This is a fine simplification, but I think we should go even further. I don’t think we want to use CrossThreadCopier. Instead we should have lambdas for each of these and copy the arguments explicitly at the call site. Need a new patch that compiles, though. EWS shows this failing to compile on most platforms. I'm all for creating manual cross-thread copies at call sites, but with C++11 lambdas this incurs an additional copy for objects of types like String. Cross-thread copies for these are created through str.isolatedCopy(), but the return value has to be copied once more when it's being value-captured by the lambda function. C++14 fixes that by providing support for init-capture -- http://isocpp.org/files/papers/N3648.html I guess this won't be perfect until we make C++14 mandatory. Until then we can either stick to CrossThreadTask and CrossThreadCopier, or suffer through the additional copying overhead.
Darin Adler
Comment 4 2014-05-11 23:24:13 PDT
(In reply to comment #3) > I'm all for creating manual cross-thread copies at call sites, but with C++11 lambdas this incurs an additional copy for objects of types like String. Sure, but lets keep in mind that “copy” here just means a ref/deref pair. I think that’s an OK cost.
Zan Dobersek
Comment 5 2014-05-12 03:25:53 PDT
(In reply to comment #4) > (In reply to comment #3) > > I'm all for creating manual cross-thread copies at call sites, but with C++11 lambdas this incurs an additional copy for objects of types like String. > > Sure, but lets keep in mind that “copy” here just means a ref/deref pair. I think that’s an OK cost. OK, I'll give it a look.
Zan Dobersek
Comment 6 2014-05-12 03:32:17 PDT
Created attachment 231284 [details] Patch
Zan Dobersek
Comment 7 2014-05-12 13:17:11 PDT
Comment on attachment 231284 [details] Patch Clearing flags on attachment: 231284 Committed r168640: <http://trac.webkit.org/changeset/168640>
Zan Dobersek
Comment 8 2014-05-12 13:17:18 PDT
All reviewed patches have been landed. Closing bug.
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