Most recent kernel where this bug did not occur: n/a
Distribution: n/a
Hardware Environment: x86 and others
Software Environment: n/a
Problem Description:
According to POSIX.1, the process nice value (as set by setpriority(), 
http://www.opengroup.org/onlinepubs/009695399/functions/getpriority.html ) 
is a process-wide attribute (at least for System Contention Scope 
threads, which is the kind of thread model used on Linux).  
However, on Linux it is a per-thread attribute.  This is a 
violation of POSIX.1,and should be remedied.
Steps to reproduce:
The following program can be used to demonstrate that the nice value 
is not shared by the threads of a process:

/* thread_share_nice.c */

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <limits.h>
#include <string.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

#define errExit(msg)            { perror(msg); exit(EXIT_FAILURE); }

#define errExitEN(en, msg)      { errno = en; perror(msg); \
                                  exit(EXIT_FAILURE); }

#define fatalExit(msg)          { fprintf(stderr, "%s\n", msg); \
                                  exit(EXIT_FAILURE); }

#define NEW_NICE 1              /* Must not be non-negative */

static void *
tf1_nice(void *x)
{
    int nval;

    errno = 0;
    nval = getpriority(PRIO_PROCESS, 0);
    if (nval == -1 && errno != 0) errExit("getpriority");
    printf("Thread 1: initial nice value is %d\n", nval);

    if (setpriority(PRIO_PROCESS, 0, NEW_NICE) == -1)
        errExit("setpriority");

    errno = 0;
    nval = getpriority(PRIO_PROCESS, 0);
    if (nval == -1 && errno != 0) errExit("getpriority");
    printf("Thread 1: nice value is %d\n", nval);

    printf("Thread 1 terminating\n");
    return NULL;
}

static void *
tf2_nice(void *x)
{
    int nval;

    errno = 0;
    nval = getpriority(PRIO_PROCESS, 0);
    if (nval == -1 && errno != 0) errExit("getpriority");

    printf("Thread 2: nice value is %d\n", nval);

    printf("nice value %s shared\n",
            (nval == NEW_NICE) ? "is" : "**IS NOT**");
    return NULL;
}

int
main(int argc, char *argv[])
{
    pthread_t t1, t2;
    void *res;
    int s;

    system("uname -a; date");

    printf("-------- nice value test --------\n");

    s = pthread_create(&t1, NULL, tf1_nice, (void *) 1);
    if (s != 0) errExitEN(s, "pthread_create");
    s = pthread_join(t1, &res);
    if (s != 0) errExitEN(s, "pthread_join");

    printf("About to create thread 2\n");

    s = pthread_create(&t2, NULL, tf2_nice, (void *) 2);
    if (s != 0) errExitEN(s, "pthread_create");
    s = pthread_join(t2, &res);
    if (s != 0) errExitEN(s, "pthread_join");

    exit(EXIT_SUCCESS);
} /* main */