If any RPC fails, the reply port will already be deallocated.
__pthread_thread_terminate thus has to defer taking its name until the very last
__thread_terminate_release which doesn't reply a message. But then we
have to read from the pthread structure.
This introduces __pthread_dealloc_finish() which does the recording of
the thread termination, so the slot can be reused really only just before
the __thread_terminate_release call. Only the real thread can set it, so
let's decouple this from the pthread_state by just removing the
PTHREAD_TERMINATED state and add a terminated field.
---
htl/pt-alloc.c | 5 +++--
htl/pt-create.c | 6 +++++-
htl/pt-dealloc.c | 13 ++++++++-----
htl/pt-detach.c | 6 ------
htl/pt-internal.h | 16 +++++++++++-----
htl/pt-join.c | 6 ------
sysdeps/mach/htl/pt-thread-terminate.c | 26 +++++++++++++++++---------
7 files changed, 44 insertions(+), 34 deletions(-)
@@ -54,6 +54,7 @@ initialize_pthread (struct __pthread *new)
new->state_lock = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER;
new->state_cond = (pthread_cond_t) PTHREAD_COND_INITIALIZER;
+ new->terminated = FALSE;
memset (&new->res_state, '\0', sizeof (new->res_state));
@@ -84,10 +85,10 @@ __pthread_alloc (struct __pthread **pthread)
{
/* There is no need to take NEW->STATE_LOCK: if NEW is on this
list, then it is protected by __PTHREAD_FREE_THREADS_LOCK
- except in __pthread_dealloc where after it is added to the
+ except in __pthread_dealloc_finish where after it is added to the
list (with the lock held), it drops the lock and then sets
NEW->STATE and immediately stops using NEW. */
- if (new->state == PTHREAD_TERMINATED)
+ if (new->terminated)
{
__pthread_dequeue (new);
break;
@@ -256,7 +256,10 @@ __pthread_create_internal (struct __pthread **thread,
failed_starting:
/* If joinable, a reference was added for the caller. */
if (pthread->state == PTHREAD_JOINABLE)
- __pthread_dealloc (pthread);
+ {
+ __pthread_dealloc (pthread);
+ __pthread_dealloc_finish (pthread);
+ }
__pthread_setid (pthread->thread, NULL);
atomic_decrement (&__pthread_total);
@@ -278,6 +281,7 @@ failed_thread_alloc:
/ __vm_page_size) * __vm_page_size + stacksize);
failed_stack_alloc:
__pthread_dealloc (pthread);
+ __pthread_dealloc_finish (pthread);
failed:
return err;
}
@@ -29,12 +29,10 @@ extern struct __pthread *__pthread_free_threads;
extern pthread_mutex_t __pthread_free_threads_lock;
-/* Deallocate the thread structure for PTHREAD. */
+/* Deallocate the content of the thread structure for PTHREAD. */
void
__pthread_dealloc (struct __pthread *pthread)
{
- assert (pthread->state != PTHREAD_TERMINATED);
-
if (!atomic_decrement_and_test (&pthread->nr_refs))
return;
@@ -56,13 +54,18 @@ __pthread_dealloc (struct __pthread *pthread)
__pthread_mutex_lock (&__pthread_free_threads_lock);
__pthread_enqueue (&__pthread_free_threads, pthread);
__pthread_mutex_unlock (&__pthread_free_threads_lock);
+}
- /* Setting PTHREAD->STATE to PTHREAD_TERMINATED makes this TCB
+/* Confirm deallocation of the thread structure for PTHREAD. */
+void
+__pthread_dealloc_finish (struct __pthread *pthread)
+{
+ /* Setting PTHREAD->TERMINATED makes this TCB
available for reuse. After that point, we can no longer assume
that PTHREAD is valid.
Note that it is safe to not lock this update to PTHREAD->STATE:
the only way that it can now be accessed is in __pthread_alloc,
which reads this variable. */
- pthread->state = PTHREAD_TERMINATED;
+ pthread->terminated = TRUE;
}
@@ -62,12 +62,6 @@ __pthread_detach (pthread_t thread)
__pthread_dealloc (pthread);
break;
- case PTHREAD_TERMINATED:
- /* Pretend THREAD wasn't there in the first place. */
- __pthread_mutex_unlock (&pthread->state_lock);
- err = ESRCH;
- break;
-
default:
/* Thou shalt not detach non-joinable threads! */
__pthread_mutex_unlock (&pthread->state_lock);
@@ -48,8 +48,6 @@ enum pthread_state
PTHREAD_DETACHED,
/* A joinable thread exited and its return code is available. */
PTHREAD_EXITED,
- /* The thread structure is unallocated and available for reuse. */
- PTHREAD_TERMINATED
};
#ifndef PTHREAD_KEY_MEMBERS
@@ -95,6 +93,8 @@ struct __pthread
enum pthread_state state;
pthread_mutex_t state_lock; /* Locks the state. */
pthread_cond_t state_cond; /* Signalled when the state changes. */
+ bool terminated; /* Whether the kernel thread is over
+ and we can reuse this structure. */
/* Resolver state. */
struct __res_state res_state;
@@ -209,12 +209,18 @@ extern int __pthread_create_internal (struct __pthread **__restrict pthread,
kernel thread or a stack). THREAD has one reference. */
extern int __pthread_alloc (struct __pthread **thread);
-/* Deallocate the thread structure. This is the dual of
+/* Deallocate the content of the thread structure. This is the dual of
__pthread_alloc (N.B. it does not call __pthread_stack_dealloc nor
- __pthread_thread_terminate). THREAD loses one reference and is
- released if the reference counter drops to 0. */
+ __pthread_thread_terminate). THREAD loses one reference, and if
+ if the reference counter drops to 0 this returns 1, and the caller has
+ to call __pthread_dealloc_finish when it is really finished with using
+ THREAD. */
extern void __pthread_dealloc (struct __pthread *thread);
+/* Confirm deallocating the thread structure. Before calling this
+ the structure will not be reused yet. */
+extern void __pthread_dealloc_finish (struct __pthread *pthread);
+
/* Allocate a stack of size STACKSIZE. The stack base shall be
returned in *STACKADDR. */
@@ -75,12 +75,6 @@ __pthread_join_common (pthread_t thread, void **status, int try,
__pthread_dealloc (pthread);
break;
- case PTHREAD_TERMINATED:
- /* Pretend THREAD wasn't there in the first place. */
- __pthread_mutex_unlock (&pthread->state_lock);
- err = ESRCH;
- break;
-
default:
/* Thou shalt not join non-joinable threads! */
__pthread_mutex_unlock (&pthread->state_lock);
@@ -35,6 +35,7 @@ __pthread_thread_terminate (struct __pthread *thread)
void *stackaddr;
size_t stacksize;
error_t err;
+ int self;
kernel_thread = thread->kernel_thread;
@@ -52,25 +53,32 @@ __pthread_thread_terminate (struct __pthread *thread)
wakeup_port = thread->wakeupmsg.msgh_remote_port;
- /* Each thread has its own reply port, allocated from MiG stub code calling
- __mig_get_reply_port. Destroying it is a bit tricky because the calls
- involved are also RPCs, causing the creation of a new reply port if
- currently null. The __thread_terminate_release call is actually a one way
- simple routine designed not to require a reply port. */
self_ktid = __mach_thread_self ();
- reply_port = (self_ktid == kernel_thread)
- ? __mig_get_reply_port () : MACH_PORT_NULL;
+ self = self_ktid == kernel_thread;
__mach_port_deallocate (__mach_task_self (), self_ktid);
/* The kernel thread won't be there any more. */
thread->kernel_thread = MACH_PORT_DEAD;
- /* Finally done with the thread structure. */
+ /* Release thread resources. */
__pthread_dealloc (thread);
- /* The wake up port is now no longer needed. */
+ /* The wake up port (needed for locks in __pthread_dealloc) is now no longer
+ needed. */
__mach_port_destroy (__mach_task_self (), wakeup_port);
+ /* Each thread has its own reply port, allocated from MiG stub code calling
+ __mig_get_reply_port. Destroying it is a bit tricky because the calls
+ involved are also RPCs, causing the creation of a new reply port if
+ currently null. The __thread_terminate_release call is actually a one way
+ simple routine designed not to require a reply port. */
+ reply_port = self ? __mig_get_reply_port () : MACH_PORT_NULL;
+ /* From here we shall not use a MIG reply port any more. */
+
+ /* Finally done with the thread structure (we still needed it to access the
+ reply port). */
+ __pthread_dealloc_finish (thread);
+
/* Terminate and release all that's left. */
err = __thread_terminate_release (kernel_thread, mach_task_self (),
kernel_thread, reply_port,