manager.c

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/* Linuxthreads - a simple clone()-based implementation of Posix        */
/* threads for Linux.                                                   */
/* Copyright (C) 1996 Xavier Leroy ([e-mail])              */
/*                                                                      */
/* This program is free software; you can redistribute it and/or        */
/* modify it under the terms of the GNU Library General Public License  */
/* as published by the Free Software Foundation; either version 2       */
/* of the License, or (at your option) any later version.               */
/*                                                                      */
/* This program is distributed in the hope that it will be useful,      */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
/* GNU Library General Public License for more details.                 */

/* The "thread manager" thread: manages creation and termination of threads */

/* mods for uClibc: getpwd and getpagesize are the syscalls */
#define __getpid getpid
#define __getpagesize getpagesize

#include <features.h>
#define __USE_GNU
#include <errno.h>
#include <sched.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/poll.h>		/* for poll */
#include <sys/mman.h>           /* for mmap */
#include <sys/param.h>
#include <sys/time.h>
#include <sys/wait.h>           /* for waitpid macros */

#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "restart.h"
#include "semaphore.h"
#include "debug.h" /* PDEBUG, added by StS */


/* poll() is not supported in kernel <= 2.0, therefore is __NR_poll is
 * not available, we assume an old Linux kernel is in use and we will
 * use select() instead. */
#include <sys/syscall.h>
#ifndef __NR_poll
# define USE_SELECT
#endif


/* Array of active threads. Entry 0 is reserved for the initial thread. */
struct pthread_handle_struct __pthread_handles[PTHREAD_THREADS_MAX] =
{ { __LOCK_INITIALIZER, &__pthread_initial_thread, 0},
  { __LOCK_INITIALIZER, &__pthread_manager_thread, 0}, /* All NULLs */ };

/* For debugging purposes put the maximum number of threads in a variable.  */
const int __linuxthreads_pthread_threads_max = PTHREAD_THREADS_MAX;

/* Indicate whether at least one thread has a user-defined stack (if 1),
   or if all threads have stacks supplied by LinuxThreads (if 0). */
int __pthread_nonstandard_stacks;

/* Number of active entries in __pthread_handles (used by gdb) */
volatile int __pthread_handles_num = 2;

/* Whether to use debugger additional actions for thread creation
   (set to 1 by gdb) */
volatile int __pthread_threads_debug;

/* Globally enabled events.  */
volatile td_thr_events_t __pthread_threads_events;

/* Pointer to thread descriptor with last event.  */
volatile pthread_descr __pthread_last_event;

/* Mapping from stack segment to thread descriptor. */
/* Stack segment numbers are also indices into the __pthread_handles array. */
/* Stack segment number 0 is reserved for the initial thread. */

static inline pthread_descr thread_segment(int seg)
{
  return (pthread_descr)(THREAD_STACK_START_ADDRESS - (seg - 1) * STACK_SIZE)
         - 1;
}

/* Flag set in signal handler to record child termination */

static volatile int terminated_children = 0;

/* Flag set when the initial thread is blocked on pthread_exit waiting
   for all other threads to terminate */

static int main_thread_exiting = 0;

/* Counter used to generate unique thread identifier.
   Thread identifier is pthread_threads_counter + segment. */

static pthread_t pthread_threads_counter = 0;

/* Forward declarations */

static int pthread_handle_create(pthread_t *thread, const pthread_attr_t *attr,
                                 void * (*start_routine)(void *), void *arg,
                                 sigset_t *mask, int father_pid,
				 int report_events,
				 td_thr_events_t *event_maskp);
static void pthread_handle_free(pthread_t th_id);
static void pthread_handle_exit(pthread_descr issuing_thread, int exitcode);
static void pthread_reap_children(void);
static void pthread_kill_all_threads(int sig, int main_thread_also);

/* The server thread managing requests for thread creation and termination */

int __pthread_manager(void *arg)
{
  int reqfd = (int) (long int) arg;
#ifdef USE_SELECT
  struct timeval tv;
  fd_set fd;
#else
  struct pollfd ufd;
#endif
  sigset_t manager_mask;
  int n;
  struct pthread_request request;

  /* If we have special thread_self processing, initialize it.  */
#ifdef INIT_THREAD_SELF
  INIT_THREAD_SELF(&__pthread_manager_thread, 1);
#endif
  /* Set the error variable.  */
  __pthread_manager_thread.p_errnop = &__pthread_manager_thread.p_errno;
  __pthread_manager_thread.p_h_errnop = &__pthread_manager_thread.p_h_errno;

#ifdef __UCLIBC_HAS_XLOCALE__
  /* Initialize thread's locale to the global locale. */
  __pthread_manager_thread.locale = __global_locale;
#endif /* __UCLIBC_HAS_XLOCALE__ */

  /* Block all signals except __pthread_sig_cancel and SIGTRAP */
  sigfillset(&manager_mask);
  sigdelset(&manager_mask, __pthread_sig_cancel); /* for thread termination */
  sigdelset(&manager_mask, SIGTRAP);            /* for debugging purposes */
  if (__pthread_threads_debug && __pthread_sig_debug > 0)
      sigdelset(&manager_mask, __pthread_sig_debug);
  sigprocmask(SIG_SETMASK, &manager_mask, NULL);
  /* Raise our priority to match that of main thread */
  __pthread_manager_adjust_prio(__pthread_main_thread->p_priority);
  /* Synchronize debugging of the thread manager */
  n = TEMP_FAILURE_RETRY(__libc_read(reqfd, (char *)&request,
				     sizeof(request)));
  ASSERT(n == sizeof(request) && request.req_kind == REQ_DEBUG);
#ifndef USE_SELECT
  ufd.fd = reqfd;
  ufd.events = POLLIN;
#endif
  /* Enter server loop */
  while(1) {
#ifdef USE_SELECT
    tv.tv_sec = 2;
    tv.tv_usec = 0;
    FD_ZERO (&fd);
    FD_SET (reqfd, &fd);
    n = select (reqfd + 1, &fd, NULL, NULL, &tv);
#else
PDEBUG("before poll\n");
    n = poll(&ufd, 1, 2000);
PDEBUG("after poll\n");
#endif
    /* Check for termination of the main thread */
    if (getppid() == 1) {
      pthread_kill_all_threads(SIGKILL, 0);
      _exit(0);
    }
    /* Check for dead children */
    if (terminated_children) {
      terminated_children = 0;
      pthread_reap_children();
    }
    /* Read and execute request */
#ifdef USE_SELECT
    if (n == 1)
#else
    if (n == 1 && (ufd.revents & POLLIN))
#endif
    {

PDEBUG("before __libc_read\n");
      n = __libc_read(reqfd, (char *)&request, sizeof(request));
PDEBUG("after __libc_read, n=%d\n", n);
      ASSERT(n == sizeof(request));
      switch(request.req_kind) {
      case REQ_CREATE:
PDEBUG("got REQ_CREATE\n");
        request.req_thread->p_retcode =
          pthread_handle_create((pthread_t *) &request.req_thread->p_retval,
                                request.req_args.create.attr,
                                request.req_args.create.fn,
                                request.req_args.create.arg,
                                &request.req_args.create.mask,
                                request.req_thread->p_pid,
				request.req_thread->p_report_events,
				&request.req_thread->p_eventbuf.eventmask);
PDEBUG("restarting %d\n", request.req_thread);
        restart(request.req_thread);
        break;
      case REQ_FREE:
PDEBUG("got REQ_FREE\n");
	pthread_handle_free(request.req_args.free.thread_id);
        break;
      case REQ_PROCESS_EXIT:
PDEBUG("got REQ_PROCESS_EXIT from %d, exit code = %d\n", 
		request.req_thread, request.req_args.exit.code);
        pthread_handle_exit(request.req_thread,
                            request.req_args.exit.code);
        break;
      case REQ_MAIN_THREAD_EXIT:
PDEBUG("got REQ_MAIN_THREAD_EXIT\n");
        main_thread_exiting = 1;
	/* Reap children in case all other threads died and the signal handler
	   went off before we set main_thread_exiting to 1, and therefore did
	   not do REQ_KICK. */
	pthread_reap_children();

        if (__pthread_main_thread->p_nextlive == __pthread_main_thread) {
          restart(__pthread_main_thread);
	  /* The main thread will now call exit() which will trigger an
	     __on_exit handler, which in turn will send REQ_PROCESS_EXIT
	     to the thread manager. In case you are wondering how the
	     manager terminates from its loop here. */
	}
        break;
      case REQ_POST:
PDEBUG("got REQ_POST\n");
        __new_sem_post(request.req_args.post);
        break;
      case REQ_DEBUG:
PDEBUG("got REQ_DEBUG\n");
	/* Make gdb aware of new thread and gdb will restart the
	   new thread when it is ready to handle the new thread. */
	if (__pthread_threads_debug && __pthread_sig_debug > 0) {
PDEBUG("about to call raise(__pthread_sig_debug)\n");
	  raise(__pthread_sig_debug);
	}
      case REQ_KICK:
	/* This is just a prod to get the manager to reap some
	   threads right away, avoiding a potential delay at shutdown. */
	break;
      }
    }
  }
}

int __pthread_manager_event(void *arg)
{
  /* If we have special thread_self processing, initialize it.  */
#ifdef INIT_THREAD_SELF
  INIT_THREAD_SELF(&__pthread_manager_thread, 1);
#endif

  /* Get the lock the manager will free once all is correctly set up.  */
  __pthread_lock (THREAD_GETMEM((&__pthread_manager_thread), p_lock), NULL);
  /* Free it immediately.  */
  __pthread_unlock (THREAD_GETMEM((&__pthread_manager_thread), p_lock));

  return __pthread_manager(arg);
}

/* Process creation */
static int
__attribute__ ((noreturn))
pthread_start_thread(void *arg)
{
  pthread_descr self = (pthread_descr) arg;
  struct pthread_request request;
  void * outcome;
  /* Initialize special thread_self processing, if any.  */
#ifdef INIT_THREAD_SELF
  INIT_THREAD_SELF(self, self->p_nr);
#endif
PDEBUG("\n");
  /* Make sure our pid field is initialized, just in case we get there
     before our father has initialized it. */
  THREAD_SETMEM(self, p_pid, __getpid());
  /* Initial signal mask is that of the creating thread. (Otherwise,
     we'd just inherit the mask of the thread manager.) */
  sigprocmask(SIG_SETMASK, &self->p_start_args.mask, NULL);
  /* Set the scheduling policy and priority for the new thread, if needed */
  if (THREAD_GETMEM(self, p_start_args.schedpolicy) >= 0)
    /* Explicit scheduling attributes were provided: apply them */
    sched_setscheduler(THREAD_GETMEM(self, p_pid),
			 THREAD_GETMEM(self, p_start_args.schedpolicy),
                         &self->p_start_args.schedparam);
  else if (__pthread_manager_thread.p_priority > 0)
    /* Default scheduling required, but thread manager runs in realtime
       scheduling: switch new thread to SCHED_OTHER policy */
    {
      struct sched_param default_params;
      default_params.sched_priority = 0;
      sched_setscheduler(THREAD_GETMEM(self, p_pid),