break_socketblocking_on_termination_v1.patch

diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index 59204cf..f01c140 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -76,6 +76,7 @@
 
 #include "libpq/libpq.h"
 #include "tcop/tcopprot.h"
+#include "miscadmin.h"
 #include "utils/memutils.h"
 
 
@@ -323,6 +324,41 @@ rloop:
 }
 
 /*
+ * Although we basically should try to send all data staying in our send
+ * buffer, we also should consider the possibility that hanging of clients or
+ * network cutoff has compelled send(2) to be blokced. We need to be allowed
+ * to exit from send() if such blocking states last for a while during process
+ * termination. Returns true if send blocking is detected.
+ *
+ * The worse side of this would be that extra-slow receiver (specifically
+ * under one packet per second) might fail to recive the result to the end,
+ * but pg_terminate_backend() is such a thing.
+ */
+static bool
+is_write_blocked(int fd)
+{
+#ifndef WIN32
+	fd_set wfds;
+	struct timeval tv;
+	int ret;
+	int save_errno = errno;
+
+	FD_ZERO(&wfds);
+	FD_SET(fd, &wfds);
+	tv.tv_sec = 1;
+	tv.tv_usec = 0;
+	ret = select(fd + 1, NULL, &wfds, NULL, &tv);
+
+	/* The error of select here is safely ignorable. */
+	errno = save_errno;
+
+	return ret <= 0 ? true : false;
+#else
+	return false;
+#endif
+}
+
+/*
  *	Write data to a secure connection.
  */
 ssize_t
@@ -457,6 +493,14 @@ wloop:
 #endif
 		n = send(port->sock, ptr, len, 0);
 
+	/*
+	 * Check for interrupt if the socket was blocked during process is
+	 * being terminated.
+	 */
+	if (ProcDiePending && is_write_blocked(port->sock))
+		CHECK_FOR_INTERRUPTS();
+	
+	
 	return n;
 }
 
@@ -515,6 +559,14 @@ my_sock_write(BIO *h, const char *buf, int size)
 
 	res = send(h->num, buf, size, 0);
 	BIO_clear_retry_flags(h);
+
+	/*
+	 * Check for interrupt if the socket was blocked during process is being
+	 * terminated.
+	 */
+	if (ProcDiePending && is_write_blocked(h->num))
+		CHECK_FOR_INTERRUPTS();
+
 	if (res <= 0)
 	{
 		if (errno == EINTR)