So what you are saying is that when pthread_attr_init() checked for the magic number in supposedly uninitialized memory it found the exact value of the magic number? That seems highly suspect. Seems like it may be pointing to a valid previous entry.
Tim Canham JPL Flight Software -----Original Message----- From: Corinna Vinschen [mailto:corinna-cyg...@cygwin.com] Sent: Wednesday, April 20, 2016 3:50 AM To: cygwin@cygwin.com Cc: Canham, Timothy K (348C) <timothy.k.can...@jpl.nasa.gov> Subject: Re: pthread_attr_init() returning errors 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
