patrick keshishian <[email protected]> writes:
> On Tue, Jan 28, 2014 at 09:02:31PM -0800, Philip Guenther wrote:
>> On Tue, Jan 28, 2014 at 4:55 PM, patrick keshishian <[email protected]>
>> wrote:
>> > Not sure if anyone is interested in this panic as the
>> > snapshot is a bit old.
>> >
>> > Happend while gdb-ing a process.
>> >
>> > (typing off images; expect typos)
>> >
>> > login: panic: kernel diagnostic assertion "__mp_lock_held(&sched_lock) ==
>> > 0" failed: file "../../../../lock.c", line 126
>>
>> That's the bug I was working on at the start of the n2k14 hackathon.
>> I've managed to simplify some of the bits underneath it, so maybe I
>> can get the intermediate problem (recursive tsleep() usage)
>> resolved...
>
> Thanks.
>
>> > Side note 1:
>> > Incidentally, I couldn't figure out how to correctly leave
>> > a symbol unresolved while compiling myapp, until dlopen()
>> > time.
>>
>> If you can include the shared-object/library in the link command line,
>> then the symbol can be referenced at link time. That lets you refer
>> to the symbols directly as if they were in the executable itself,
>> though you must still declare them for the compiler to know what type
>> they are, etc.
>
> A bit of a chicken-and-egg situation for this case. Unless
> I do some ugly "hopping" around in Makefiles, it would be
> difficult to include the object on the link line for the
> main program.
>
>> If you need to delay the loading of the shared-object until after
>> process startup via dlopen(), then the executable should use dlsym()
>> to get the symbol address, passing it the handle that dlopen()
>> returned.
>
> Yes. I do that right now with a bit of "dance". However,
> reading a bit about __attribute__((weak)) on-line, I
> thought, there may be an easier way to achieve this. But,
> I quite possibly misunderstood the use of that attribute.
It sounds like you're not using dlsym as intended, then. If you used:
void (*my_function)(void);
my_function = dlsym(handle, "target_function");
if (my_function == NULL)
oops();
(*my_function)();
then your program wouldn't need to reference target_function at all.
[...]
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