Fix timeout/cond signal race causing extra restart signal to be generated

but not consumed.

1 files changed, 109 insertions, 46 deletions

diff --git a/devel/linuxthreads/files/condwait-patch b/devel/linuxthreads/files/condwait-patch
index cbd6cefb81c9..5e9c45a2392a 100644
--- a/devel/linuxthreads/files/condwait-patch
+++ b/devel/linuxthreads/files/condwait-patch
@@ -1,16 +1,19 @@
-diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
---- ../../work.orig/linuxthreads-2.2.3_1/condvar.c	Thu Apr 12 21:02:02 2001
-+++ ./condvar.c	Wed Jul 18 13:30:47 2001
-@@ -55,6 +55,8 @@
+diff -ru ../../work.nc/linuxthreads-2.2.3_19/condvar.c ./condvar.c
+--- ../../work.nc/linuxthreads-2.2.3_19/condvar.c	Thu Apr 12 23:02:02 2001
++++ ./condvar.c	Tue Jan 10 18:14:20 2006
+@@ -55,6 +55,11 @@
    return did_remove;
  }
  
 +extern int __pthread_mutex_condwait_completelock(pthread_mutex_t *mutex);
 +
++#define CVA_AVAIL 1
++#define CVA_EXTRA_RESTART 2
++
  int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
  {
    volatile pthread_descr self = thread_self();
-@@ -74,6 +76,7 @@
+@@ -74,6 +79,7 @@
  
    /* Register extrication interface */
    THREAD_SETMEM(self, p_condvar_avail, 0);
@@ -18,13 +21,30 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
    __pthread_set_own_extricate_if(self, &extr);
  
    /* Atomically enqueue thread for waiting, but only if it is not
-@@ -121,15 +124,35 @@
+@@ -102,10 +108,15 @@
+   while (1)
+     {
+       suspend(self);
+-      if (THREAD_GETMEM(self, p_condvar_avail) == 0
++      if ((THREAD_GETMEM(self, p_condvar_avail) & CVA_AVAIL) == 0
+ 	  && (THREAD_GETMEM(self, p_woken_by_cancel) == 0
+ 	      || THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE))
+ 	{
++	  if ((THREAD_GETMEM(self, p_condvar_avail) &
++	       CVA_EXTRA_RESTART) == 0 &&
++	      !__compare_and_swap(&self->p_condvar_avail,
++				  0, CVA_EXTRA_RESTART))
++	    break;		/* CVA_AVAIL set by other thread */
+ 	  /* Count resumes that don't belong to us. */
+ 	  spurious_wakeup_count++;
+ 	  continue;
+@@ -121,15 +132,35 @@
    if (THREAD_GETMEM(self, p_woken_by_cancel)
        && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
      THREAD_SETMEM(self, p_woken_by_cancel, 0);
 -    pthread_mutex_lock(mutex);
 +    if (THREAD_GETMEM(self, p_condwait_mutex) == NULL) {
-+      if (THREAD_GETMEM(self, p_condwait_extra_restart) != 0) {
++      if ((THREAD_GETMEM(self, p_condvar_avail) & CVA_EXTRA_RESTART) != 0) {
 +	if (spurious_wakeup_count > 0)
 +	  spurious_wakeup_count--;
 +	else
@@ -37,7 +57,7 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
    }
  
 +  if (THREAD_GETMEM(self, p_condwait_mutex) == NULL &&
-+      THREAD_GETMEM(self, p_condwait_extra_restart) != 0) {
++      (THREAD_GETMEM(self, p_condvar_avail) & CVA_EXTRA_RESTART) != 0) {
 +    if (spurious_wakeup_count > 0)
 +      spurious_wakeup_count--;
 +    else
@@ -56,7 +76,7 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
    return 0;
  }
  
-@@ -155,6 +178,7 @@
+@@ -155,6 +186,7 @@
  
    /* Register extrication interface */
    THREAD_SETMEM(self, p_condvar_avail, 0);
@@ -64,13 +84,30 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
    __pthread_set_own_extricate_if(self, &extr);
  
    /* Enqueue to wait on the condition and check for cancellation. */
-@@ -215,15 +239,35 @@
+@@ -196,10 +228,15 @@
+ 	suspend(self);
+       }
+ 
+-      if (THREAD_GETMEM(self, p_condvar_avail) == 0
++      if ((THREAD_GETMEM(self, p_condvar_avail) & CVA_AVAIL) == 0
+ 	  && (THREAD_GETMEM(self, p_woken_by_cancel) == 0
+ 	      || THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE))
+ 	{
++	  if ((THREAD_GETMEM(self, p_condvar_avail) &
++	       CVA_EXTRA_RESTART) == 0 &&
++	      !__compare_and_swap(&self->p_condvar_avail,
++				0, CVA_EXTRA_RESTART))
++	    break;		/* CVA_AVAIL set by other thread */
+ 	  /* Count resumes that don't belong to us. */
+ 	  spurious_wakeup_count++;
+ 	  continue;
+@@ -215,15 +252,35 @@
    if (THREAD_GETMEM(self, p_woken_by_cancel)
        && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
      THREAD_SETMEM(self, p_woken_by_cancel, 0);
 -    pthread_mutex_lock(mutex);
 +    if (THREAD_GETMEM(self, p_condwait_mutex) == NULL) {
-+      if (THREAD_GETMEM(self, p_condwait_extra_restart) != 0) {
++      if ((THREAD_GETMEM(self, p_condvar_avail) & CVA_EXTRA_RESTART) != 0) {
 +	if (spurious_wakeup_count > 0)
 +	  spurious_wakeup_count--;
 +	else
@@ -83,7 +120,7 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
    }
  
 +  if (THREAD_GETMEM(self, p_condwait_mutex) == NULL &&
-+      THREAD_GETMEM(self, p_condwait_extra_restart) != 0) {
++      (THREAD_GETMEM(self, p_condvar_avail) & CVA_EXTRA_RESTART) != 0) {
 +    if (spurious_wakeup_count > 0)
 +      spurious_wakeup_count--;
 +    else
@@ -102,7 +139,13 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
    return 0;
  }
  
-@@ -242,9 +286,27 @@
+@@ -237,14 +294,34 @@
+ int pthread_cond_signal(pthread_cond_t *cond)
+ {
+   pthread_descr th;
++  long oldcva;
+ 
+   __pthread_lock(&cond->__c_lock, NULL);
    th = dequeue(&cond->__c_waiting);
    __pthread_unlock(&cond->__c_lock);
    if (th != NULL) {
@@ -110,30 +153,39 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
 -    WRITE_MEMORY_BARRIER();
 -    restart(th);
 +    pthread_mutex_t *mutex = th->p_condwait_mutex;
-+    if (th->p_condvar_avail == 0 &&
++    if ((th->p_condvar_avail & CVA_AVAIL) == 0 &&
 +	mutex != NULL &&
 +	(mutex->__m_kind == PTHREAD_MUTEX_ERRORCHECK_NP ||
 +	 mutex->__m_kind == PTHREAD_MUTEX_TIMED_NP) &&
 +	__pthread_alt_condwait_queuelock(&mutex->__m_lock, th) == 0) {
 +      th->p_condwait_mutex = NULL;
-+      th->p_condwait_extra_restart = 0;
 +      WRITE_MEMORY_BARRIER();
-+      th->p_condvar_avail = 1;
++      do {
++	READ_MEMORY_BARRIER();
++	oldcva = th->p_condvar_avail;
++      } while (!__compare_and_swap(&th->p_condvar_avail,
++				   oldcva,
++				   oldcva | CVA_AVAIL));
 +      WRITE_MEMORY_BARRIER();
-+      if (th->p_condwait_waitnode.abandoned) {
-+	th->p_condwait_extra_restart = 1;
-+	WRITE_MEMORY_BARRIER();
++      if ((th->p_condvar_avail & CVA_EXTRA_RESTART) != 0)
 +	restart(th);
-+      }
 +    } else {
-+      th->p_condvar_avail = 1;
++      th->p_condvar_avail = CVA_AVAIL;
 +      WRITE_MEMORY_BARRIER();
 +      restart(th);
 +    }
    }
    return 0;
  }
-@@ -260,9 +322,27 @@
+@@ -252,6 +329,7 @@
+ int pthread_cond_broadcast(pthread_cond_t *cond)
+ {
+   pthread_descr tosignal, th;
++  long oldcva;
+ 
+   __pthread_lock(&cond->__c_lock, NULL);
+   /* Copy the current state of the waiting queue and empty it */
+@@ -260,9 +338,28 @@
    __pthread_unlock(&cond->__c_lock);
    /* Now signal each process in the queue */
    while ((th = dequeue(&tosignal)) != NULL) {
@@ -141,32 +193,34 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/condvar.c ./condvar.c
 -    WRITE_MEMORY_BARRIER();
 -    restart(th);
 +    pthread_mutex_t *mutex = th->p_condwait_mutex;
-+    if (th->p_condvar_avail == 0 &&
++    if ((th->p_condvar_avail & CVA_AVAIL) == 0 &&
 +	mutex != NULL &&
 +	(mutex->__m_kind == PTHREAD_MUTEX_ERRORCHECK_NP ||
 +	 mutex->__m_kind == PTHREAD_MUTEX_TIMED_NP) &&
 +	__pthread_alt_condwait_queuelock(&mutex->__m_lock, th) == 0) {
 +      th->p_condwait_mutex = NULL;
-+      th->p_condwait_extra_restart = 0;
 +      WRITE_MEMORY_BARRIER();
-+      th->p_condvar_avail = 1;
++      do {
++	READ_MEMORY_BARRIER();
++	oldcva = th->p_condvar_avail;
++      } while (!__compare_and_swap(&th->p_condvar_avail,
++				   oldcva,
++				   oldcva | CVA_AVAIL));
 +      WRITE_MEMORY_BARRIER();
-+      if (th->p_condwait_waitnode.abandoned) {
-+	th->p_condwait_extra_restart = 1;
-+	WRITE_MEMORY_BARRIER();
++      if ((th->p_condvar_avail & CVA_EXTRA_RESTART) != 0)
 +	restart(th);
-+      }
 +    } else {
-+      th->p_condvar_avail = 1;
++      th->p_condvar_avail = CVA_AVAIL;
 +      WRITE_MEMORY_BARRIER();
 +      restart(th);
 +    }
    }
    return 0;
  }
-diff -ru ../../work.orig/linuxthreads-2.2.3_1/internals.h ./internals.h
---- ../../work.orig/linuxthreads-2.2.3_1/internals.h	Wed Jul 18 07:25:04 2001
-+++ ./internals.h	Wed Jul 18 10:55:57 2001
+Only in .: condvar.c~
+diff -ru ../../work.nc/linuxthreads-2.2.3_19/internals.h ./internals.h
+--- ../../work.nc/linuxthreads-2.2.3_19/internals.h	Tue Jan 10 17:13:14 2006
++++ ./internals.h	Tue Jan 10 17:33:30 2006
 @@ -125,6 +125,13 @@
    int pr_lock_count;
  } pthread_readlock_info;
@@ -181,19 +235,28 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/internals.h ./internals.h
  struct _pthread_descr_struct {
    union {
      struct {
-@@ -189,6 +196,9 @@
+@@ -176,7 +183,7 @@
+   struct pthread_atomic p_resume_count; /* number of times restart() was
+ 					   called on thread */
+   char p_woken_by_cancel;       /* cancellation performed wakeup */
+-  char p_condvar_avail;		/* flag if conditional variable became avail */
++  long p_condvar_avail;		/* flag if conditional variable became avail */
+   char p_sem_avail;             /* flag if semaphore became available */
+   pthread_extricate_if *p_extricate; /* See above */
+   pthread_readlock_info *p_readlock_list;  /* List of readlock info structs */
+@@ -189,6 +196,8 @@
    hp_timing_t p_cpuclock_offset; /* Initial CPU clock for thread.  */
  #endif
    /* New elements must be added at the end.  */
 +  pthread_mutex_t *p_condwait_mutex;
 +  struct wait_node p_condwait_waitnode;
-+  char p_condwait_extra_restart;
  } __attribute__ ((aligned(32))); /* We need to align the structure so that
  				    doubles are aligned properly.  This is 8
  				    bytes on MIPS and 16 bytes on MIPS64.
-diff -ru ../../work.orig/linuxthreads-2.2.3_1/mutex.c ./mutex.c
---- ../../work.orig/linuxthreads-2.2.3_1/mutex.c	Sun Jan  7 04:35:20 2001
-+++ ./mutex.c	Wed Jul 18 09:09:13 2001
+Only in .: internals.h~
+diff -ru ../../work.nc/linuxthreads-2.2.3_19/mutex.c ./mutex.c
+--- ../../work.nc/linuxthreads-2.2.3_19/mutex.c	Sun Jan  7 05:35:20 2001
++++ ./mutex.c	Tue Jan 10 17:13:46 2006
 @@ -92,6 +92,24 @@
  }
  strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
@@ -219,10 +282,10 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/mutex.c ./mutex.c
  int __pthread_mutex_lock(pthread_mutex_t * mutex)
  {
    pthread_descr self;
-diff -ru ../../work.orig/linuxthreads-2.2.3_1/spinlock.c ./spinlock.c
---- ../../work.orig/linuxthreads-2.2.3_1/spinlock.c	Wed Jul 18 07:25:04 2001
-+++ ./spinlock.c	Wed Jul 18 10:56:34 2001
-@@ -232,12 +232,6 @@
+diff -ru ../../work.nc/linuxthreads-2.2.3_19/spinlock.c ./spinlock.c
+--- ../../work.nc/linuxthreads-2.2.3_19/spinlock.c	Tue Jan 10 17:13:14 2006
++++ ./spinlock.c	Tue Jan 10 17:13:46 2006
+@@ -231,12 +231,6 @@
   */
  
  
@@ -235,7 +298,7 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/spinlock.c ./spinlock.c
  static long wait_node_free_list;
  #if !defined HAS_COMPARE_AND_SWAP || defined TEST_FOR_COMPARE_AND_SWAP
  static int wait_node_free_list_spinlock;
-@@ -360,6 +354,55 @@
+@@ -359,6 +353,55 @@
  }
  
  #endif
@@ -291,9 +354,9 @@ diff -ru ../../work.orig/linuxthreads-2.2.3_1/spinlock.c ./spinlock.c
  
  void __pthread_alt_lock(struct _pthread_fastlock * lock,
  		        pthread_descr self)
-diff -ru ../../work.orig/linuxthreads-2.2.3_1/spinlock.h ./spinlock.h
---- ../../work.orig/linuxthreads-2.2.3_1/spinlock.h	Wed Jul 18 07:25:04 2001
-+++ ./spinlock.h	Wed Jul 18 09:14:58 2001
+diff -ru ../../work.nc/linuxthreads-2.2.3_19/spinlock.h ./spinlock.h
+--- ../../work.nc/linuxthreads-2.2.3_19/spinlock.h	Tue Jan 10 17:13:14 2006
++++ ./spinlock.h	Tue Jan 10 17:13:46 2006
 @@ -130,6 +130,9 @@
     timed-out waits.  Warning: do not mix these operations with the above ones
     over the same lock object! */