diff options
Diffstat (limited to 'nptl/pthread_cond_wait.c')
| -rw-r--r-- | nptl/pthread_cond_wait.c | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/nptl/pthread_cond_wait.c b/nptl/pthread_cond_wait.c new file mode 100644 index 0000000000..f5f5cec5a8 --- /dev/null +++ b/nptl/pthread_cond_wait.c @@ -0,0 +1,191 @@ +/* Copyright (C) 2003, 2004, 2006 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003. + + 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <endian.h> +#include <errno.h> +#include <sysdep.h> +#include <lowlevellock.h> +#include <pthread.h> +#include <pthreadP.h> + +#include <shlib-compat.h> + + +struct _condvar_cleanup_buffer +{ + int oldtype; + pthread_cond_t *cond; + pthread_mutex_t *mutex; + unsigned int bc_seq; +}; + + +void +__attribute__ ((visibility ("hidden"))) +__condvar_cleanup (void *arg) +{ + struct _condvar_cleanup_buffer *cbuffer = + (struct _condvar_cleanup_buffer *) arg; + unsigned int destroying; + + /* We are going to modify shared data. */ + lll_mutex_lock (cbuffer->cond->__data.__lock); + + if (cbuffer->bc_seq == cbuffer->cond->__data.__broadcast_seq) + { + /* This thread is not waiting anymore. Adjust the sequence counters + appropriately. We do not increment WAKEUP_SEQ if this would + bump it over the value of TOTAL_SEQ. This can happen if a thread + was woken and then canceled. */ + if (cbuffer->cond->__data.__wakeup_seq + < cbuffer->cond->__data.__total_seq) + { + ++cbuffer->cond->__data.__wakeup_seq; + ++cbuffer->cond->__data.__futex; + } + ++cbuffer->cond->__data.__woken_seq; + } + + cbuffer->cond->__data.__nwaiters -= 1 << COND_CLOCK_BITS; + + /* If pthread_cond_destroy was called on this variable already, + notify the pthread_cond_destroy caller all waiters have left + and it can be successfully destroyed. */ + destroying = 0; + if (cbuffer->cond->__data.__total_seq == -1ULL + && cbuffer->cond->__data.__nwaiters < (1 << COND_CLOCK_BITS)) + { + lll_futex_wake (&cbuffer->cond->__data.__nwaiters, 1); + destroying = 1; + } + + /* We are done. */ + lll_mutex_unlock (cbuffer->cond->__data.__lock); + + /* Wake everybody to make sure no condvar signal gets lost. */ + if (! destroying) + lll_futex_wake (&cbuffer->cond->__data.__futex, INT_MAX); + + /* Get the mutex before returning unless asynchronous cancellation + is in effect. */ + __pthread_mutex_cond_lock (cbuffer->mutex); +} + + +int +__pthread_cond_wait (cond, mutex) + pthread_cond_t *cond; + pthread_mutex_t *mutex; +{ + struct _pthread_cleanup_buffer buffer; + struct _condvar_cleanup_buffer cbuffer; + int err; + + /* Make sure we are along. */ + lll_mutex_lock (cond->__data.__lock); + + /* Now we can release the mutex. */ + err = __pthread_mutex_unlock_usercnt (mutex, 0); + if (__builtin_expect (err, 0)) + { + lll_mutex_unlock (cond->__data.__lock); + return err; + } + + /* We have one new user of the condvar. */ + ++cond->__data.__total_seq; + ++cond->__data.__futex; + cond->__data.__nwaiters += 1 << COND_CLOCK_BITS; + + /* Remember the mutex we are using here. If there is already a + different address store this is a bad user bug. Do not store + anything for pshared condvars. */ + if (cond->__data.__mutex != (void *) ~0l) + cond->__data.__mutex = mutex; + + /* Prepare structure passed to cancellation handler. */ + cbuffer.cond = cond; + cbuffer.mutex = mutex; + + /* Before we block we enable cancellation. Therefore we have to + install a cancellation handler. */ + __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer); + + /* The current values of the wakeup counter. The "woken" counter + must exceed this value. */ + unsigned long long int val; + unsigned long long int seq; + val = seq = cond->__data.__wakeup_seq; + /* Remember the broadcast counter. */ + cbuffer.bc_seq = cond->__data.__broadcast_seq; + + do + { + unsigned int futex_val = cond->__data.__futex; + + /* Prepare to wait. Release the condvar futex. */ + lll_mutex_unlock (cond->__data.__lock); + + /* Enable asynchronous cancellation. Required by the standard. */ + cbuffer.oldtype = __pthread_enable_asynccancel (); + + /* Wait until woken by signal or broadcast. */ + lll_futex_wait (&cond->__data.__futex, futex_val); + + /* Disable asynchronous cancellation. */ + __pthread_disable_asynccancel (cbuffer.oldtype); + + /* We are going to look at shared data again, so get the lock. */ + lll_mutex_lock (cond->__data.__lock); + + /* If a broadcast happened, we are done. */ + if (cbuffer.bc_seq != cond->__data.__broadcast_seq) + goto bc_out; + + /* Check whether we are eligible for wakeup. */ + val = cond->__data.__wakeup_seq; + } + while (val == seq || cond->__data.__woken_seq == val); + + /* Another thread woken up. */ + ++cond->__data.__woken_seq; + + bc_out: + + cond->__data.__nwaiters -= 1 << COND_CLOCK_BITS; + + /* If pthread_cond_destroy was called on this varaible already, + notify the pthread_cond_destroy caller all waiters have left + and it can be successfully destroyed. */ + if (cond->__data.__total_seq == -1ULL + && cond->__data.__nwaiters < (1 << COND_CLOCK_BITS)) + lll_futex_wake (&cond->__data.__nwaiters, 1); + + /* We are done with the condvar. */ + lll_mutex_unlock (cond->__data.__lock); + + /* The cancellation handling is back to normal, remove the handler. */ + __pthread_cleanup_pop (&buffer, 0); + + /* Get the mutex before returning. */ + return __pthread_mutex_cond_lock (mutex); +} + +versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait, + GLIBC_2_3_2); |