pthread_attr_init() returning errors
Corinna Vinschen
corinna-cygwin@cygwin.com
Wed Apr 20 10:54:00 GMT 2016
On Apr 19 19:49, Canham, Timothy K (348C) wrote:
> I have some code to start a task that suddenly started failing. This is pretty mature code. Here is the code fragment with my added printf()
>
> pthread_attr_t att;
> int stat = pthread_attr_init(&att);
> if (stat != 0) {
> printf("pthread_attr_init: (%d)(%d): %s\n",stat,errno,strerror(stat));
> // return
> }
>
> Here is the output:
>
> pthread_attr_init: (16)(0): Device or resource busy
This is most unusual. What happens is this:
A pthread_attr_t is a pointer to a pointer to a struct with a magic
number. And at the start of pthread_attr_init this magic number is
tested if it's already the magic number expected for an object of type
pthread_attr_t. And only if so, the pthread_attr_init function fails
with EBUSY.
That means, the arbitrary value in the uninitialized att prior to
the call to pthread_attr_init is a pointer value which points to
valid memory which has the magic value 0xdf0df048. Wow.
This means we can't keep up with the tests in the pthread_FOO_init
functions since they could point to an *supposedly* initialized
object, while in fact the value they point to is only accidentally
so that it looks like an initialized object.
I provided new developer snapshots on https://cygwin.com/snapshots/
and I've just uploaded a 2.5.1-0.1 test release which you can install
via setup as soon as your mirror has catched up.
Pleaser give any of them a try.
Thanks,
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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