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/* Copyright (C) 2002-2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <sched.h>
#include <setjmp.h>
#include <signal.h>
#include <stdlib.h>
#include <atomic.h>
#include <ldsodefs.h>
#include <tls.h>
#include <stdint.h>
#include "kernel-features.h"
#define CLONE_SIGNAL (CLONE_SIGHAND | CLONE_THREAD)
/* Unless otherwise specified, the thread "register" is going to be
initialized with a pointer to the TCB. */
#ifndef TLS_VALUE
# define TLS_VALUE pd
#endif
#ifndef ARCH_CLONE
# define ARCH_CLONE __clone
#endif
#ifndef TLS_MULTIPLE_THREADS_IN_TCB
/* Pointer to the corresponding variable in libc. */
int *__libc_multiple_threads_ptr attribute_hidden;
#endif
static int
do_clone (struct pthread *pd, const struct pthread_attr *attr,
int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
int stopped)
{
#ifdef PREPARE_CREATE
PREPARE_CREATE;
#endif
if (__glibc_unlikely (stopped != 0))
/* We make sure the thread does not run far by forcing it to get a
lock. We lock it here too so that the new thread cannot continue
until we tell it to. */
lll_lock (pd->lock, LLL_PRIVATE);
/* One more thread. We cannot have the thread do this itself, since it
might exist but not have been scheduled yet by the time we've returned
and need to check the value to behave correctly. We must do it before
creating the thread, in case it does get scheduled first and then
might mistakenly think it was the only thread. In the failure case,
we momentarily store a false value; this doesn't matter because there
is no kosher thing a signal handler interrupting us right here can do
that cares whether the thread count is correct. */
atomic_increment (&__nptl_nthreads);
int rc = ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
pd, &pd->tid, TLS_VALUE, &pd->tid);
if (__glibc_unlikely (rc == -1))
{
atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second. */
/* Perhaps a thread wants to change the IDs and if waiting
for this stillborn thread. */
if (__builtin_expect (atomic_exchange_acq (&pd->setxid_futex, 0)
== -2, 0))
lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
/* Free the resources. */
__deallocate_stack (pd);
/* We have to translate error codes. */
return errno == ENOMEM ? EAGAIN : errno;
}
/* Now we have the possibility to set scheduling parameters etc. */
if (__glibc_unlikely (stopped != 0))
{
INTERNAL_SYSCALL_DECL (err);
int res = 0;
/* Set the affinity mask if necessary. */
if (attr->cpuset != NULL)
{
res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
attr->cpusetsize, attr->cpuset);
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err)))
{
/* The operation failed. We have to kill the thread. First
send it the cancellation signal. */
INTERNAL_SYSCALL_DECL (err2);
err_out:
(void) INTERNAL_SYSCALL (tgkill, err2, 3,
THREAD_GETMEM (THREAD_SELF, pid),
pd->tid, SIGCANCEL);
/* We do not free the stack here because the canceled thread
itself will do this. */
return (INTERNAL_SYSCALL_ERROR_P (res, err)
? INTERNAL_SYSCALL_ERRNO (res, err)
: 0);
}
}
/* Set the scheduling parameters. */
if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
{
res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
pd->schedpolicy, &pd->schedparam);
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err)))
goto err_out;
}
}
/* We now have for sure more than one thread. The main thread might
not yet have the flag set. No need to set the global variable
again if this is what we use. */
THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
return 0;
}
static int
create_thread (struct pthread *pd, const struct pthread_attr *attr,
STACK_VARIABLES_PARMS)
{
#if TLS_TCB_AT_TP
assert (pd->header.tcb != NULL);
#endif
/* We rely heavily on various flags the CLONE function understands:
CLONE_VM, CLONE_FS, CLONE_FILES
These flags select semantics with shared address space and
file descriptors according to what POSIX requires.
CLONE_SIGNAL
This flag selects the POSIX signal semantics.
CLONE_SETTLS
The sixth parameter to CLONE determines the TLS area for the
new thread.
CLONE_PARENT_SETTID
The kernels writes the thread ID of the newly created thread
into the location pointed to by the fifth parameters to CLONE.
Note that it would be semantically equivalent to use
CLONE_CHILD_SETTID but it is be more expensive in the kernel.
CLONE_CHILD_CLEARTID
The kernels clears the thread ID of a thread that has called
sys_exit() in the location pointed to by the seventh parameter
to CLONE.
The termination signal is chosen to be zero which means no signal
is sent. */
int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
| CLONE_SETTLS | CLONE_PARENT_SETTID
| CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
| 0);
if (__glibc_unlikely (THREAD_GETMEM (THREAD_SELF, report_events)))
{
/* The parent thread is supposed to report events. Check whether
the TD_CREATE event is needed, too. */
const int _idx = __td_eventword (TD_CREATE);
const uint32_t _mask = __td_eventmask (TD_CREATE);
if ((_mask & (__nptl_threads_events.event_bits[_idx]
| pd->eventbuf.eventmask.event_bits[_idx])) != 0)
{
/* We always must have the thread start stopped. */
pd->stopped_start = true;
/* Create the thread. We always create the thread stopped
so that it does not get far before we tell the debugger. */
int res = do_clone (pd, attr, clone_flags, start_thread,
STACK_VARIABLES_ARGS, 1);
if (res == 0)
{
/* Now fill in the information about the new thread in
the newly created thread's data structure. We cannot let
the new thread do this since we don't know whether it was
already scheduled when we send the event. */
pd->eventbuf.eventnum = TD_CREATE;
pd->eventbuf.eventdata = pd;
/* Enqueue the descriptor. */
do
pd->nextevent = __nptl_last_event;
while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
pd, pd->nextevent)
!= 0);
/* Now call the function which signals the event. */
__nptl_create_event ();
/* And finally restart the new thread. */
lll_unlock (pd->lock, LLL_PRIVATE);
}
return res;
}
}
#ifdef NEED_DL_SYSINFO
assert (THREAD_SELF_SYSINFO == THREAD_SYSINFO (pd));
#endif
/* Determine whether the newly created threads has to be started
stopped since we have to set the scheduling parameters or set the
affinity. */
bool stopped = false;
if (attr != NULL && (attr->cpuset != NULL
|| (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
stopped = true;
pd->stopped_start = stopped;
pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
/* Actually create the thread. */
int res = do_clone (pd, attr, clone_flags, start_thread,
STACK_VARIABLES_ARGS, stopped);
if (res == 0 && stopped)
/* And finally restart the new thread. */
lll_unlock (pd->lock, LLL_PRIVATE);
return res;
}
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