/* Copyright (C) 2002-2014 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper , 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 . */ #include #include #include #include #include #include #include #include #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) { #ifdef 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; }