Re: System threads (pthreads)

Mike Abbott wrote:
>> I'm interested in as many details as you can spare.
> 
> On 2002-11-26 Gene wrote this:
> | I did some digging in the linuxthreads source.  I think the
> | culprit is in the inlined function thread_self() which is called
> | by __errno_location().  That function relies on stack pointer to
> | get pthread's identity.  The "stack pointer" is just an address
> | of a local variable:
> | 
> | #define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
> | char *sp = CURRENT_STACK_FRAME;
> | 
> | In other words, libpthread assumes that there is only one stack
> | per each pthread and thus thread id can be inferred from the
> | stack pointer.  If there are stack segments other than created
> | by libpthread, thread_self() may return bogus thread id.
> | 
> | The bottom line, I guess, is that current pthreads implementation
> | cannot be mixed with any other thread library.
> | 
> | --Gene
> 
> I remember discussing other issues, in particular a collision on some
> special memory location, but I don't recall the details.
> 
> Interop between ST and pthreads comes up repeatedly though, so if you
> find a fix we'd love to receive it.
> 
> 
> 
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Is ST really incompatible with OS threads?  This simple test works, but 
I've also been writing a real application where I just started mixing 
pthreads and state-threads, and it seems there are no problems so far, 
but I'm afraid I'm missing something.  Is there an example of something 
that breaks?  (Also, if ST really doesn't work--how does Pth manage to 
coexist with pthreads?)

// Demonstrates ST compatibility with OS threads.

#include <iostream>
#include <pthread.h>
#include <st.h>
#include <unistd.h>

using namespace std;

void *f(void *p) {
   cout << "hello" << endl;
   st_sleep(1);
   cout << "goodbye" << endl;
   return 0;
}

void *F(void *p) {
   cout << "HELLO" << endl;
   sleep(1);
   cout << "GOODBYE" << endl;
   return 0;
}

int main() {
   st_init();
   st_thread_t t1 = st_thread_create(f, 0, 1, 0);
   st_thread_t t2 = st_thread_create(f, 0, 1, 0);

   pthread_t T;
   pthread_create(&T, NULL, F, 0);

   st_thread_join(t1, 0);
   st_thread_join(t2, 0);

   pthread_join(T, 0);

   return 0;
}
-- 
Yang Zhang
http://www.mit.edu/~y_z/

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