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Re: [PATCH] Make it possible to annotate the shared pointer operations in the std::thread implementation
On Sat, Dec 24, 2011 at 12:05 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 24 December 2011 11:46, Bart Van Assche wrote:
>> Would it be acceptable to replace the
>> _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE() and ..._AFTER() macros by
>> something like this:
>>
>> ?if (pf) (*pf)(addr, before_or_after_flag)
>>
>> where pf is a function pointer that is NULL by default and can be set
>> by libstdc++ users. That approach would also avoid that libstdc++ has
>> to be recompiled in order to instrument reference count decrementing
>> for data race detectors.
>
> I think the cost of checking that on every ref-count update would be
> too high for the vast majority of users who don't use race detectors.
> A macro has zero cost if it's not used, and even people using race
> detectors don't want them enabled all the time. As I said, you don't
> need to recompile the whole library to instrument the parts that are
> affected, only specific objects. ?I think the right thing to do is
> identify the parts that need to be recompiled and document how to do
> just that.
Would it be technically possible to implement a binary patching
approach in a user space shared library similar to the binary patching
technique used in the kprobe implementation in the Linux kernel ?
For more information, see also
http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git;a=blob;f=Documentation/kprobes.txt.
Bart.
Bart.