Redesigned how cancellation unblocks a thread from internal cancellation points (sem_wait, pthread_join, pthread_cond_{wait,timedwait}). Cancellation won't eat a signal in any of these functions (*required* by POSIX and Single Unix Spec!).

2000-01-03  Kaz Kylheku  <kaz@ashi.footprints.net>

	Redesigned how cancellation unblocks a thread from internal
	cancellation points (sem_wait, pthread_join,
	pthread_cond_{wait,timedwait}).
	Cancellation won't eat a signal in any of these functions
	(*required* by POSIX and Single Unix Spec!).
	* condvar.c: spontaneous wakeup on pthread_cond_timedwait won't eat a
	simultaneous condition variable signal (not required by POSIX
	or Single Unix Spec, but nice).
	* spinlock.c: __pthread_lock queues back any received restarts
	that don't belong to it instead of assuming ownership of lock
	upon any restart; fastlock can no longer be acquired by two threads
	simultaneously.
	* restart.h: restarts queue even on kernels that don't have
	queued real time signals (2.0, early 2.1), thanks to atomic counter,
	avoiding a rare race condition in pthread_cond_timedwait.

1 files changed, 40 insertions, 0 deletions

diff --git a/linuxthreads/internals.h b/linuxthreads/internals.h
index c5fde1f883..8af2fca335 100644
--- a/linuxthreads/internals.h
+++ b/linuxthreads/internals.h
@@ -86,6 +86,27 @@ struct pthread_key_struct {
 
 typedef struct _pthread_descr_struct * pthread_descr;
 
+/* Callback interface for removing the thread from waiting on an
+   object if it is cancelled while waiting or about to wait.
+   This hold a pointer to the object, and a pointer to a function
+   which ``extricates'' the thread from its enqueued state.
+   The function takes two arguments: pointer to the wait object,
+   and a pointer to the thread. It returns 1 if an extrication
+   actually occured, and hence the thread must also be signalled.
+   It returns 0 if the thread had already been extricated. */
+
+typedef struct _pthread_extricate_struct {
+    void *pu_object;
+    int (*pu_extricate_func)(void *, pthread_descr);
+} pthread_extricate_if;
+
+/* Atomic counter made possible by compare_and_swap */
+
+struct pthread_atomic {
+  long p_count;
+  int p_spinlock;
+};
+
 struct _pthread_descr_struct {
   pthread_descr p_nextlive, p_prevlive;
                                 /* Double chaining of active threads */
@@ -96,6 +117,7 @@ struct _pthread_descr_struct {
   int p_priority;               /* Thread priority (== 0 if not realtime) */
   struct _pthread_fastlock * p_lock; /* Spinlock for synchronized accesses */
   int p_signal;                 /* last signal received */
+  struct pthread_atomic p_resume_count; /* number of times restart() was called on thread */
   sigjmp_buf * p_signal_jmp;    /* where to siglongjmp on a signal or NULL */
   sigjmp_buf * p_cancel_jmp;    /* where to siglongjmp on a cancel or NULL */
   char p_terminated;            /* true if terminated e.g. by pthread_exit */
@@ -108,6 +130,8 @@ struct _pthread_descr_struct {
   char p_cancelstate;           /* cancellation state */
   char p_canceltype;            /* cancellation type (deferred/async) */
   char p_canceled;              /* cancellation request pending */
+  char p_woken_by_cancel;       /* cancellation performed wakeup */
+  pthread_extricate_if *p_extricate; /* See above */
   int * p_errnop;               /* pointer to used errno variable */
   int p_errno;                  /* error returned by last system call */
   int * p_h_errnop;             /* pointer to used h_errno variable */
@@ -353,6 +377,7 @@ void __pthread_manager_sighandler(int sig);
 void __pthread_reset_main_thread(void);
 void __fresetlockfiles(void);
 void __pthread_manager_adjust_prio(int thread_prio);
+void __pthread_set_own_extricate_if(pthread_descr self, pthread_extricate_if *peif);
 
 extern int __pthread_attr_setguardsize (pthread_attr_t *__attr,
 					size_t __guardsize);
@@ -372,6 +397,21 @@ extern int __pthread_mutexattr_gettype (const pthread_mutexattr_t *__attr,
 					int *__kind);
 extern void __pthread_kill_other_threads_np (void);
 
+void __pthread_restart_old(pthread_descr th);
+void __pthread_suspend_old(pthread_descr self);
+
+void __pthread_restart_new(pthread_descr th);
+void __pthread_suspend_new(pthread_descr self);
+
+void __pthread_wait_for_restart_signal(pthread_descr self);
+
+void __pthread_init_condvar(int rt_sig_available);
+
+/* Global pointers to old or new suspend functions */
+
+extern void (*__pthread_restart)(pthread_descr);
+extern void (*__pthread_suspend)(pthread_descr);
+
 /* Prototypes for the function without cancelation support when the
    normal version has it.  */
 extern int __libc_close (int fd);