TLS on powerpc(32/64)

Prosun Niyogi
2006-09-21T23:20:53Z

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Hi,
I've been struggling the last few days on getting gdb
to work correctly on a powerpc64 machine. Built as
ppc-64-linux, debugging ppc64 binaries linked against
libpthread. It seems to me that gdb's TLS access does
not work correctly on these platforms. Attempting to
print a variable of type __thread doesnt work.

Here's a paste:

shadows:~/pniyogi # ldd ./tls
linux-vdso64.so.1 => (0x0000000000100000)
libpthread.so.0 => /lib64/libpthread.so.0
libgcc_s.so.1 => /lib64/libgcc_s.so.1
libc.so.6 => /lib64/libc.so.6
/lib64/ld64.so.1 (0x0000040000000000)
shadows:~/pniyogi # ./gdb-new ./tls
GNU gdb 6.5.50.20060811-cvs
***********
(gdb) b 80
Breakpoint 1 at 0x10000d6c: file tls.c, line 80.
(gdb) r
Starting program: /root/pniyogi/tls
[New LWP 8210]
[Switching to LWP 8210]

Breakpoint 1, spin (vp=0x0) at tls.c:80
80 thread_local_val[ me ] = a_thread_local;
(gdb) p a_thread_local
Cannot find thread-local variables on this target
(gdb)

Also attaching a testcase tls.c that I was compiling
with -m64 -g

Any assistance/insight would be appreciated.

-Prosun Niyogi

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/* BeginSourceFile tls.c

This file creates and deletes threads. It uses thread local storage
variables too. */

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <pthread.h>
#include <semaphore.h>
#include <errno.h>

#define N_THREADS 3

/* Uncomment to turn on debugging output */
/*#define START_DEBUG*/

/* Thread-local storage. */
__thread int a_thread_local;
__thread int another_thread_local;

/* Global variable just for info addr in gdb. */
int a_global;

/* Print the results of thread-local storage. */
int thread_local_val[ N_THREADS ];
int another_thread_local_val[ N_THREADS ];

/* Semaphores to make sure the threads are alive when we print the TLS
variables from gdb. */
sem_t tell_main, tell_thread;

void print_error ()
{
switch (errno)
{
case EAGAIN:
fprintf (stderr, "EAGAIN\n");
break;
case EINTR:
fprintf (stderr, "EINTR\n");
break;
case EINVAL:
fprintf (stderr, "EINVAL\n");
break;
case ENOSYS:
fprintf (stderr, "ENOSYS\n");
break;
case ENOENT:
fprintf (stderr, "ENOENT\n");
break;
case EDEADLK:
fprintf (stderr, "EDEADLK\n");
break;
default:
fprintf (stderr, "Unknown error\n");
break;
}
}

/* Routine for each thread to run, does nothing. */
void *spin( vp )
void * vp;
{
int me = (long) vp;
int i;

/* Use a_global. */
a_global++;

a_thread_local = 0;
another_thread_local = me;
for( i = 0; i <= me; i++ ) {
a_thread_local += i;
printf("Thread local = %d\n", a_thread_local);

}

another_thread_local_val[me] = another_thread_local;
thread_local_val[ me ] = a_thread_local; /* here we know tls value */

if (sem_post (&tell_main) == -1)
{
fprintf (stderr, "th %d post on sem tell_main failed\n", me);
print_error ();
return;
}
#ifdef START_DEBUG
fprintf (stderr, "th %d post on tell main\n", me);
#endif

while (1)
{
#ifdef START_DEBUG
fprintf (stderr, "th %d start wait on tell_thread\n", me);
#endif
if (sem_wait (&tell_thread) == 0)
break;

if (errno == EINTR)
{
#ifdef START_DEBUG
fprintf (stderr, "th %d wait tell_thread got EINTR, rewaiting\n", me);
#endif
continue;
}
else
{
fprintf (stderr, "th %d wait on sem tell_thread failed\n", me);
print_error ();
return;
}
}

#ifdef START_DEBUG
fprintf (stderr, "th %d Wait on tell_thread\n", me);
#endif

}

void
do_pass()
{
int i;
pthread_t t[ N_THREADS ];
int err;

for( i = 0; i < N_THREADS; i++)
{
thread_local_val[i] = 0;
another_thread_local_val[i] = 0;
}

if (sem_init (&tell_main, 0, 0) == -1)
{
fprintf (stderr, "tell_main semaphore init failed\n");
return;
}

if (sem_init (&tell_thread, 0, 0) == -1)
{
fprintf (stderr, "tell_thread semaphore init failed\n");
return;
}

/* Start N_THREADS threads, then join them so that they are terminated. */
for( i = 0; i < N_THREADS; i++ )
{
err = pthread_create( &t[i], NULL, spin, (void *) (long) i );
if( err != 0 ) {
fprintf(stderr, "Error in thread %d create\n", i );
}
}

for( i = 0; i < N_THREADS; i++ )
{
while (1)
{
#ifdef START_DEBUG
fprintf (stderr, "main %d start wait on tell_main\n", i);
#endif
if (sem_wait (&tell_main) == 0)
break;

if (errno == EINTR)
{
#ifdef START_DEBUG
fprintf (stderr, "main %d wait tell_main got EINTR, rewaiting\n", i);
#endif
continue;
}
else
{
fprintf (stderr, "main %d wait on sem tell_main failed\n", i);
print_error ();
return;
}
}
}

#ifdef START_DEBUG
fprintf (stderr, "main done waiting on tell_main\n");
#endif

i = 10; /* Here all threads should be still alive. */

for( i = 0; i < N_THREADS; i++ )
{
if (sem_post (&tell_thread) == -1)
{
fprintf (stderr, "main %d post on sem tell_thread failed\n", i);
print_error ();
return;
}
#ifdef START_DEBUG
fprintf (stderr, "main %d post on tell_thread\n", i);
#endif
}

for( i = 0; i < N_THREADS; i++ )
{
err = pthread_join(t[i], NULL );
if( err != 0 )
{
fprintf (stderr, "error in thread %d join\n", i );
}
}

i = 10; /* Null line for setting bpts on. */

}

int
main()
{
do_pass ();

return 0; /* Set breakpoint here before exit. */
}

/* EndSourceFile */