From 9fb4573f5f4ef54b440fa38e536b60694c5d8506 Mon Sep 17 00:00:00 2001
From: "sfraser%netscape.com" <sfraser%netscape.com>
Date: Sat, 14 Apr 2001 01:10:27 +0000
Subject: [PATCH] These changes fix PR_Poll on Mac thusly:
1. Factor out
 checking the fds into a new function CheckPollDescs()
2. Factor out
 setting/clearing the polling thread on those fds into 
SetDescPollThread()
3.
 Be more careful about where we set the polling thread on the fds, ensuring 
 
  that we turn off interrupts and hold a lock around the code that sets up the
    polling thread and checks for data on the fds. This fixes the race
 condition
   that causes this bug.
4. We now clear the polling thread on the
 fds when coming out of PR_Poll, so that
   the notifier doesn't attempt to
 wake the wrong thread when called when
   we're not polling.
5. Implement a
 0-timeout version that behaves like select().

Bugzilla bugs 72965 and 60509.
 r=gordon, larryh.

---
 nsprpub/pr/src/md/mac/macsockotpt.c | 85 ++++++++++++++++++++++-------
 nsprpub/pr/src/md/mac/macthr.c      |  2 +
 2 files changed, 67 insertions(+), 20 deletions(-)

diff --git a/nsprpub/pr/src/md/mac/macsockotpt.c b/nsprpub/pr/src/md/mac/macsockotpt.c
index 9519efc0683..04f6c4e9eec 100644
--- a/nsprpub/pr/src/md/mac/macsockotpt.c
+++ b/nsprpub/pr/src/md/mac/macsockotpt.c
@@ -1702,19 +1702,13 @@ static PRBool GetState(PRFileDesc *fd, PRBool *readReady, PRBool *writeReady, PR
     return  *readReady || *writeReady || *exceptReady;
 }
 
-
-PRInt32 _MD_poll(PRPollDesc *pds, PRIntn npds, PRIntervalTime timeout)
+// check to see if any of the poll descriptors have data available
+// for reading or writing.
+static PRInt32 CheckPollDescs(PRPollDesc *pds, PRIntn npds)
 {
     PRInt32 ready = 0;
     PRPollDesc *pd, *epd;
-    PRThread	*thread = _PR_MD_CURRENT_THREAD();
-    PRIntervalTime timein;
     
-    if (PR_INTERVAL_NO_TIMEOUT != timeout)
-        timein = PR_IntervalNow();
-
-    do
-    {
         for (pd = pds, epd = pd + npds; pd < epd; pd++)
         {
             PRInt16  in_flags_read = 0,  in_flags_write = 0;
@@ -1746,10 +1740,9 @@ PRInt32 _MD_poll(PRPollDesc *pds, PRIntn npds, PRIntervalTime timeout)
                 pd->out_flags = 0;  /* pre-condition */
                 bottomFD = PR_GetIdentitiesLayer(pd->fd, PR_NSPR_IO_LAYER);
                 PR_ASSERT(NULL != bottomFD);
-                if ((NULL != bottomFD) && (_PR_FILEDESC_OPEN == bottomFD->secret->state))
-                {
-                    bottomFD->secret->md.poll.thread = thread;
                 	
+            if (bottomFD && (_PR_FILEDESC_OPEN == bottomFD->secret->state))
+            {
                     if (GetState(bottomFD, &readReady, &writeReady, &exceptReady))
                     {
                         if (readReady)
@@ -1773,7 +1766,7 @@ PRInt32 _MD_poll(PRPollDesc *pds, PRIntn npds, PRIntervalTime timeout)
                         if (0 != pd->out_flags) ready++;
                     }
                 }
-                else
+            else    /* bad state */
                 {
                     ready += 1;  /* this will cause an abrupt return */
                     pd->out_flags = PR_POLL_NVAL;  /* bogii */
@@ -1781,17 +1774,69 @@ PRInt32 _MD_poll(PRPollDesc *pds, PRIntn npds, PRIntervalTime timeout)
             }
         }
 
-        if (ready > 0) return ready;
+    return ready;
+}
 
-        thread->io_pending       = PR_TRUE;
-        thread->io_fd            = NULL;
-        thread->md.osErrCode     = noErr;
+// set or clear md.poll.thread on the poll descriptors
+static void SetDescPollThread(PRPollDesc *pds, PRIntn npds, PRThread* thread)
+{
+    PRInt32     ready = 0;
+    PRPollDesc *pd, *epd;
+
+    for (pd = pds, epd = pd + npds; pd < epd; pd++)
+    {   
+        if (pd->fd)
+        { 
+            PRFileDesc *bottomFD = PR_GetIdentitiesLayer(pd->fd, PR_NSPR_IO_LAYER);
+            PR_ASSERT(NULL != bottomFD);
+            if (bottomFD && (_PR_FILEDESC_OPEN == bottomFD->secret->state))
+            {
+                bottomFD->secret->md.poll.thread = thread;
+            }
+        }        
+    }
+}
+
+PRInt32 _MD_poll(PRPollDesc *pds, PRIntn npds, PRIntervalTime timeout)
+{
+    PRThread    *thread = _PR_MD_CURRENT_THREAD();
+    intn is;
+    PRInt32 ready;
+    OSErr   result;
+    
+    if (timeout == PR_INTERVAL_NO_WAIT) {        
+        return CheckPollDescs(pds, npds);
+    }
+    
+    _PR_INTSOFF(is);
+    PR_Lock(thread->md.asyncIOLock);
+
+    // ensure that we don't miss the firing of the notifier while checking socket status
+    // need to set up the thread
+    PrepareForAsyncCompletion(thread, 0);
+
+    SetDescPollThread(pds, npds, thread);        
+    ready = CheckPollDescs(pds, npds);
+
+    PR_Unlock(thread->md.asyncIOLock);
+    _PR_FAST_INTSON(is);
+
+    if (ready == 0) {
         WaitOnThisThread(thread, timeout);
+        result = thread->md.osErrCode;
+        if (result != noErr && result != kETIMEDOUTErr) {
+            PR_ASSERT(0);   /* debug: catch unexpected errors */
+            ready = -1;
+        } else {
+            ready = CheckPollDescs(pds, npds);
+        }
+    } else {
+        thread->io_pending = PR_FALSE;
+    }
 
-    } while ((timeout == PR_INTERVAL_NO_TIMEOUT) ||
-           (((PRIntervalTime)(PR_IntervalNow() - timein)) < timeout));
+    SetDescPollThread(pds, npds, NULL);
 
-    return 0; /* timed out */
+    return ready;
 }
 
 
diff --git a/nsprpub/pr/src/md/mac/macthr.c b/nsprpub/pr/src/md/mac/macthr.c
index 08ef59b9246..43f9a079724 100644
--- a/nsprpub/pr/src/md/mac/macthr.c
+++ b/nsprpub/pr/src/md/mac/macthr.c
@@ -291,6 +291,8 @@ void WaitOnThisThread(PRThread *thread, PRIntervalTime timeout)
 		thread->md.osErrCode = kETIMEDOUTErr;
 		PR_SetError(PR_IO_TIMEOUT_ERROR, kETIMEDOUTErr);
 	}
+
+	thread->io_pending = PR_FALSE;
 	PR_Unlock(thread->md.asyncIOLock);
 	_PR_FAST_INTSON(is);
 }