From 8081702460726304af496be52234385094392a6f Mon Sep 17 00:00:00 2001 From: Samuel Thibault Date: Mon, 1 Jun 2020 17:27:48 +0000 Subject: [PATCH] htl: Make pthread_cond_destroy wait for threads to be woken This allows to reuse the storage after calling pthread_cond_destroy. * sysdeps/htl/bits/types/struct___pthread_cond.h (__pthread_cond): Replace unused struct __pthread_condimpl *__impl field with unsigned int __wrefs. (__PTHREAD_COND_INITIALIZER): Update accordingly. * sysdeps/htl/pt-cond-timedwait.c (__pthread_cond_timedwait_internal): Register as waiter in __wrefs field. On unregistering, wake any pending pthread_cond_destroy. * sysdeps/htl/pt-cond-destroy.c (__pthread_cond_destroy): Register wake request in __wrefs. * nptl/Makefile (tests): Move tst-cond20 tst-cond21 to... * sysdeps/pthread/Makefile (tests): ... here. * nptl/tst-cond20.c nptl/tst-cond21.c: Move to... * sysdeps/pthread/tst-cond20.c sysdeps/pthread/tst-cond21.c: ... here. --- nptl/Makefile | 2 +- sysdeps/htl/bits/types/struct___pthread_cond.h | 4 ++-- sysdeps/htl/pt-cond-destroy.c | 18 +++++++++++++++--- sysdeps/htl/pt-cond-timedwait.c | 11 +++++++++++ sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c | 11 +++++++++++ sysdeps/pthread/Makefile | 2 +- {nptl => sysdeps/pthread}/tst-cond20.c | 0 {nptl => sysdeps/pthread}/tst-cond21.c | 0 8 files changed, 41 insertions(+), 7 deletions(-) rename {nptl => sysdeps/pthread}/tst-cond20.c (100%) rename {nptl => sysdeps/pthread}/tst-cond21.c (100%) diff --git a/nptl/Makefile b/nptl/Makefile index a13b1c3308..ae4000205f 100644 --- a/nptl/Makefile +++ b/nptl/Makefile @@ -263,7 +263,7 @@ tests = tst-attr2 tst-attr3 tst-default-attr \ tst-mutexpi1 tst-mutexpi2 tst-mutexpi3 tst-mutexpi4 \ tst-mutexpi5 tst-mutexpi5a tst-mutexpi6 tst-mutexpi7 tst-mutexpi7a \ tst-mutexpi9 \ - tst-cond20 tst-cond21 tst-cond22 tst-cond26 \ + tst-cond22 tst-cond26 \ tst-robustpi1 tst-robustpi2 tst-robustpi3 tst-robustpi4 tst-robustpi5 \ tst-robustpi6 tst-robustpi7 tst-robustpi9 \ tst-rwlock2 tst-rwlock2a tst-rwlock2b tst-rwlock3 \ diff --git a/sysdeps/htl/bits/types/struct___pthread_cond.h b/sysdeps/htl/bits/types/struct___pthread_cond.h index 150a37c4c9..c040b171ac 100644 --- a/sysdeps/htl/bits/types/struct___pthread_cond.h +++ b/sysdeps/htl/bits/types/struct___pthread_cond.h @@ -27,12 +27,12 @@ struct __pthread_cond __pthread_spinlock_t __lock; struct __pthread *__queue; struct __pthread_condattr *__attr; - struct __pthread_condimpl *__impl; + unsigned int __wrefs; void *__data; }; /* Initializer for a condition variable. */ #define __PTHREAD_COND_INITIALIZER \ - { __PTHREAD_SPIN_LOCK_INITIALIZER, NULL, NULL, NULL, NULL } + { __PTHREAD_SPIN_LOCK_INITIALIZER, NULL, NULL, 0, NULL } #endif /* bits/types/struct___pthread_cond.h */ diff --git a/sysdeps/htl/pt-cond-destroy.c b/sysdeps/htl/pt-cond-destroy.c index 0664f3f6cc..722516a8e2 100644 --- a/sysdeps/htl/pt-cond-destroy.c +++ b/sysdeps/htl/pt-cond-destroy.c @@ -22,14 +22,26 @@ int __pthread_cond_destroy (pthread_cond_t *cond) { - int ret = 0; + /* Set the wake request flag. */ + unsigned int wrefs = atomic_fetch_or_acquire (&cond->__wrefs, 1); __pthread_spin_wait (&cond->__lock); if (cond->__queue) - ret = EBUSY; + { + __pthread_spin_unlock (&cond->__lock); + return EBUSY; + } __pthread_spin_unlock (&cond->__lock); - return ret; + while (wrefs >> 1 != 0) + { + gsync_wait (__mach_task_self (), (vm_offset_t) &cond->__wrefs, wrefs, + 0, 0, 0); + wrefs = atomic_load_acquire (&cond->__wrefs); + } + /* The memory the condvar occupies can now be reused. */ + + return 0; } weak_alias (__pthread_cond_destroy, pthread_cond_destroy); diff --git a/sysdeps/htl/pt-cond-timedwait.c b/sysdeps/htl/pt-cond-timedwait.c index a0ced9a074..c05944d16d 100644 --- a/sysdeps/htl/pt-cond-timedwait.c +++ b/sysdeps/htl/pt-cond-timedwait.c @@ -144,6 +144,10 @@ __pthread_cond_timedwait_internal (pthread_cond_t *cond, /* Release MUTEX before blocking. */ __pthread_mutex_unlock (mutex); + /* Increase the waiter reference count. Relaxed MO is sufficient because + we only need to synchronize when decrementing the reference count. */ + atomic_fetch_add_relaxed (&cond->__wrefs, 2); + /* Block the thread. */ if (abstime != NULL) err = __pthread_timedblock (self, abstime, clock_id); @@ -178,6 +182,13 @@ __pthread_cond_timedwait_internal (pthread_cond_t *cond, } __pthread_spin_unlock (&cond->__lock); + /* If destruction is pending (i.e., the wake-request flag is nonzero) and we + are the last waiter (prior value of __wrefs was 1 << 1), then wake any + threads waiting in pthread_cond_destroy. Release MO to synchronize with + these threads. Don't bother clearing the wake-up request flag. */ + if ((atomic_fetch_add_release (&cond->__wrefs, -2)) == 3) + __gsync_wake (__mach_task_self (), (vm_offset_t) &cond->__wrefs, 0, 0); + if (drain) __pthread_block (self); diff --git a/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c b/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c index 939ed568ba..4f63955d04 100644 --- a/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c +++ b/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c @@ -111,6 +111,10 @@ __pthread_hurd_cond_timedwait_internal (pthread_cond_t *cond, /* Release MUTEX before blocking. */ __pthread_mutex_unlock (mutex); + /* Increase the waiter reference count. Relaxed MO is sufficient because + we only need to synchronize when decrementing the reference count. */ + atomic_fetch_add_relaxed (&cond->__wrefs, 2); + /* Block the thread. */ if (abstime != NULL) err = __pthread_timedblock (self, abstime, clock_id); @@ -144,6 +148,13 @@ __pthread_hurd_cond_timedwait_internal (pthread_cond_t *cond, __pthread_block (self); } + /* If destruction is pending (i.e., the wake-request flag is nonzero) and we + are the last waiter (prior value of __wrefs was 1 << 1), then wake any + threads waiting in pthread_cond_destroy. Release MO to synchronize with + these threads. Don't bother clearing the wake-up request flag. */ + if ((atomic_fetch_add_release (&cond->__wrefs, -2)) == 3) + __gsync_wake (__mach_task_self (), (vm_offset_t) &cond->__wrefs, 0, 0); + /* Clear the hook, now that we are done blocking. */ ss->cancel_hook = NULL; /* Check the cancellation flag; we might have unblocked due to diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile index 74dbca1890..3dc88274a7 100644 --- a/sysdeps/pthread/Makefile +++ b/sysdeps/pthread/Makefile @@ -49,7 +49,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \ tst-cond1 tst-cond2 tst-cond3 tst-cond4 tst-cond5 tst-cond6 tst-cond7 \ tst-cond8 tst-cond9 tst-cond10 tst-cond11 tst-cond12 tst-cond13 \ tst-cond14 tst-cond15 tst-cond16 tst-cond17 tst-cond18 tst-cond19 \ - tst-cond23 tst-cond24 tst-cond25 tst-cond27 \ + tst-cond20 tst-cond21 tst-cond23 tst-cond24 tst-cond25 tst-cond27 \ tst-cond-except \ tst-join1 tst-join2 tst-join3 tst-join4 tst-join5 tst-join6 tst-join7 \ tst-join8 tst-join9 tst-join10 tst-join11 tst-join12 tst-join13 \ diff --git a/nptl/tst-cond20.c b/sysdeps/pthread/tst-cond20.c similarity index 100% rename from nptl/tst-cond20.c rename to sysdeps/pthread/tst-cond20.c diff --git a/nptl/tst-cond21.c b/sysdeps/pthread/tst-cond21.c similarity index 100% rename from nptl/tst-cond21.c rename to sysdeps/pthread/tst-cond21.c