[Lldb-commits] [PATCH] fix lldb-mi hang on OSX

[Zachary Turner]

I don't work on OSX (or use lldb-mi), so it was mostly just a passing
comment. If there are no other objections I won't block it either.
On Tue, Dec 2, 2014 at 9:27 AM Ilia K <ki.stfu at gmail.com> wrote:

> Hi Zachary,
>
> We can save file descriptor once and don't use fileno() every time we need
> it but it may doesn't work and it doesn't resolve design flaw. Redesign the
> lldb-mi is a big task which can take a long time.
>
> Currently problem is that OSX's implementation of libc hangs on it in
> mutex_lock() and this patch, as I understood, avoids this behaviour.
> I think the 'select' patch should be committed as is.
>
> Thanks,
> Ilia
>
> On Tue, Dec 2, 2014 at 7:33 PM, Zachary Turner <zturner at google.com> wrote:
>
>> I kind of feel like calling fgets from one thread and fileno from another
>> thread indicates a design flaw. Is there any way to fix the design problem
>> instead of this particular bug?
>> On Tue, Dec 2, 2014 at 1:24 AM Илья К <ki.stfu at gmail.com> wrote:
>>
>>> Hello Abid,
>>>
>>> >RE: But I am still wondering why you need extra "return" in case of
>>> -exec-run. It seems to work ok on Linux. Where is it blocking in OSX?
>>> I had the same bug on OSX but "select" patch helped me (btw, thank Dawn
>>> for that).
>>> As I understood the problem occurs when trying to get filno(stdin), when
>>> another thread sleeping in fgets(stdin). The filno() starts sleeping too
>>> because stdin's mutex already locked by fgets(). Perhaps it related to
>>> OSX's libc implementation and therefore it don't reproduced on Linux.
>>>
>>> I wrote test, which doesn't works properly without WITH_SELECT_FIX:
>>> <code>
>>> #include <cstdio>
>>> #include <thread>
>>> #include <unistd.h>
>>> #include <sys/select.h>
>>>
>>> //#define WITH_SELECT_FIX
>>>
>>> void first_func()
>>> {
>>>     char buf[1024];
>>> #ifdef WITH_SELECT_FIX
>>>     fd_set inset;
>>>     FD_ZERO(&inset);
>>>     FD_SET(0, &inset);
>>>     select(1, &inset, NULL, NULL, NULL);
>>> #endif
>>>     char *line = fgets(buf, sizeof buf, stdin);
>>>     printf("you entered: %s\n", buf);
>>> }
>>>
>>> void second_func()
>>> {
>>>     usleep(100);
>>>     printf("fileno: ");
>>>     printf("%d\n", fileno(stdin));
>>> }
>>>
>>> int main()
>>> {
>>>     std::thread first(first_func);
>>>     std::thread second(second_func);
>>>     printf("start test\n");
>>>     first.join();
>>>     second.join();
>>>     printf("exiting\n");
>>>     return 0;
>>> }
>>> </code>
>>>
>>> >RE: Btw, if the problem is only with gdb-exit then an extra check for
>>> it where we check for "quit" will work too.
>>> As I said above, it doesn't solve a problem, it only fixes a certain
>>> case.
>>>
>>> So I think you should accept the Dawn's "select" patch.
>>>
>>> Thanks,
>>> Ilia
>>> _______________________________________________
>>> lldb-commits mailing list
>>> lldb-commits at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits
>>>
>>
>
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