Re: [DynInst_API:] oneTimeCode vs oneTimeCodeAsync

[Bill Williams <bill@xxxxxxxxxxx>]

On 07/22/2014 11:29 AM, Francis Deslauriers wrote:
> Hi everyone,
>
> I want to use the oneTimeCode(Async) functions and their behavior is
> not what I expected from the documentation.
>
> Here is a dummy program that triggers the problem:
>
> int main (int argc, const char* argv[]) {
> BPatch bpatch;
> BPatch_process *handle = bpatch.processCreate("./mutatee", NULL);
>
> BPatch_image *image = handle->getImage();
>
> vector<BPatch_function*> functions;
> std::vector<BPatch_snippet *> args;
>
> image->findFunction("printf", functions);
>
> BPatch_snippet *fmt = new BPatch_constExpr("oneTimeCodeAsync\n");
> args.push_back(fmt);
> BPatch_funcCallExpr firstPrintfCall(*(functions[0]), args);
> handle->oneTimeCodeAsync(firstPrintfCall);
> args.clear();
>
> fmt = new BPatch_constExpr("oneTimeCode\n");
> args.push_back(fmt);
> BPatch_funcCallExpr secondPrintfCall(*(functions[0]), args);
> handle->oneTimeCode(secondPrintfCall, NULL);
> printf("Mutator:continueExecution\n");
> handle->continueExecution();
>
> while (!handle->isTerminated())
> bpatch.waitForStatusChange();
> return 0;
> }
>
> So in this program I add two onetimecode snippets. The first one is a
> Async which would means that it would be executed after I call
> "continueExecution" and the second one is a Sync so it should be
> executed straight away.
>
> Here is what happens:
> $> env DYNINSTAPI_RT_LIB=/usr/lib/libdyninstAPI_RT.so  ./mutator
> oneTimeCodeAsync
> oneTimeCode
> Mutator: continueExecution
> Mutatee: Main
>
> Both of the calls are executed before the continueExecution.
>
> Here is what I expected :
> $> env DYNINSTAPI_RT_LIB=/usr/lib/libdyninstAPI_RT.so  ./mutator
> oneTimeCode
> Mutator: continueExecution
> oneTimeCodeAsync
> Mutatee: Main
>
> Is my understanding of the oneTimeCode* functions correct? Am I using
> a function wrong?
Both asynchronous and synchronous oneTimeCodes will post something 
immediately to the process (and find a thread to run on); the difference 
is when they will return to the user. Asynchronous oneTimeCodes will 
return immediately, with all necessary event handling happening in the 
background. You may register a callback for oneTimeCode completion to 
collect their return value. Synchronous oneTimeCodes block the calling 
thread until they're completed and consequently allow you to collect 
their return value directly.
So what you're seeing is what you should be seeing, but the 
documentation may in this case be unclear (or simply wrong).
> I attached an archive with a test case.
>
> Thanks,
>
> Francis Deslauriers
>
>
>
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--
--bw

Bill Williams
Paradyn Project
bill@xxxxxxxxxxx