From ea994aa1957bd3faea8f4cdf2ae290d102ae1fe8 Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Sat, 31 May 2014 02:30:53 +0000
Subject: Correct the interest masks in the Tcl_CreateFileHandler() calls in
 PipeWatchProc().  When we are interested in both readable and writable events
 of a command pipeline channel, we only want the readable from the read end of
 the pipe, and the writable from the write end of the pipe.

---
 generic/tclIO.c    | 17 ++++++++++++-----
 tests/io.test      |  6 ------
 unix/tclUnixPipe.c |  4 ++--
 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 0716074..1c4a5b3 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -2694,11 +2694,18 @@ FlushChannel(
 	    (chanPtr->typePtr->watchProc)(chanPtr->instanceData,
 		    statePtr->interestMask);
 	} else {
-	    /* TODO: If code reaches this point, it means a writable
-	     * event is being handled on the channel, but the channel
-	     * could not in fact be written to.  This ought not happen,
-	     * but Unix pipes appear to act this way (see io-53.4).
-	     * Also can imagine broken reflected channels. */
+
+	    /*
+	     * When we are calledFromAsyncFlush, that means a writable
+	     * state on the channel triggered the call, so we should be
+	     * able to write something.  Either we did write something 
+	     * and wroteSome should be set, or there was nothing left to
+	     * write in this call, and we've completed the BG flush.
+	     * These are the two cases above.  If we get here, that means
+	     * there is some kind failure in the writable event machinery.
+	     */
+
+	    assert(!calledFromAsyncFlush);
 	}
     }
 
diff --git a/tests/io.test b/tests/io.test
index f1248b9..2296986 100644
--- a/tests/io.test
+++ b/tests/io.test
@@ -7120,17 +7120,12 @@ test io-53.4 {CopyData: background write overflow} {stdio unix openpipe fileeven
     for {set x 0} {$x < 12} {incr x} {
 	append big $big
     }
-#    file delete $path(test1)
     file delete $path(pipe)
     set f1 [open $path(pipe) w]
     puts $f1 {
 	puts ready
 	fcopy stdin stdout -command { set x }
 	vwait x
-#	set f [open $path(test1) w]
-#	fconfigure $f -translation lf
-#	puts $f "done"
-#	close $f
     }
     close $f1
     set f1 [open "|[list [interpreter] $path(pipe)]" r+]
@@ -7138,7 +7133,6 @@ test io-53.4 {CopyData: background write overflow} {stdio unix openpipe fileeven
     fconfigure $f1 -blocking 0
     puts $f1 $big
     flush $f1
-    after 500
     set result ""
     fileevent $f1 read [namespace code {
 	append result [read $f1 1024]
diff --git a/unix/tclUnixPipe.c b/unix/tclUnixPipe.c
index d0a5e53..57be08f 100644
--- a/unix/tclUnixPipe.c
+++ b/unix/tclUnixPipe.c
@@ -1125,7 +1125,7 @@ PipeWatchProc(
     if (psPtr->inFile) {
 	newmask = mask & (TCL_READABLE | TCL_EXCEPTION);
 	if (newmask) {
-	    Tcl_CreateFileHandler(GetFd(psPtr->inFile), mask,
+	    Tcl_CreateFileHandler(GetFd(psPtr->inFile), newmask,
 		    (Tcl_FileProc *) Tcl_NotifyChannel,
 		    (ClientData) psPtr->channel);
 	} else {
@@ -1135,7 +1135,7 @@ PipeWatchProc(
     if (psPtr->outFile) {
 	newmask = mask & (TCL_WRITABLE | TCL_EXCEPTION);
 	if (newmask) {
-	    Tcl_CreateFileHandler(GetFd(psPtr->outFile), mask,
+	    Tcl_CreateFileHandler(GetFd(psPtr->outFile), newmask,
 		    (Tcl_FileProc *) Tcl_NotifyChannel,
 		    (ClientData) psPtr->channel);
 	} else {
-- 
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