From 0981b6cfe49fedf9855e42bbde1f81a89c6a4ea1 Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@systemlinux.org>
Date: Sun, 10 May 2009 17:40:42 +0200
Subject: [PATCH] filter: Force a minimal select timeout if something was
 converted.

When filter_preselect() runs. other pre_select functions might have
already been called and decided to do nothing, e.g. because their
output buffer was full or the input buffer was empty.

If this call to filter_preselect() changed any of the involved buffers,
we want those other pre_select() functions to be called ASAP. So force
a minimal timeout for the next select call to avoid unnecessary delays.
---
 filter_common.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/filter_common.c b/filter_common.c
index ebda1ee7..1b02e1cd 100644
--- a/filter_common.c
+++ b/filter_common.c
@@ -99,7 +99,7 @@ static void call_callbacks(struct filter_node *fn, char *inbuf, size_t inlen,
  * there is input available for the filter node in question. If the convert
  * function consumed some or all of its input data, all registered input
  * callbacks are called.  Similarly, if a convert function produced output, all
- * registerd output callbacks get called.
+ * registered output callbacks get called.
  *
  * On errors a (negative) error code is stored in t->error.
  *
@@ -125,8 +125,6 @@ again:
 		struct filter *f = filters + fn->filter_num;
 		if (fn->loaded < fn->bufsize) {
 			size_t size, old_fn_loaded = fn->loaded;
-//			PARA_DEBUG_LOG("fc %p loaded: %zd, calling %s convert\n",
-//				fc, *loaded, fn->filter->name);
 			t->error = f->convert(ib, *loaded, fn);
 			if (t->error < 0)
 				return;
@@ -134,24 +132,29 @@ again:
 			call_callbacks(fn, ib, size, fn->buf + old_fn_loaded,
 				fn->loaded - old_fn_loaded);
 			*loaded -= size;
-			conv += size;
-			if (*loaded && size) {
-//				PARA_DEBUG_LOG("moving %zd bytes in input "
-//					"buffer for %s filter\n",
-//					*loaded,  fn->filter->name);
+			conv += size + fn->loaded - old_fn_loaded;
+			if (*loaded && size)
 				memmove(ib, ib + size, *loaded);
-			}
 		}
 		ib = fn->buf;
 		loaded = &fn->loaded;
 	}
 	conv_total += conv;
-//	PARA_DEBUG_LOG("eof (in/out/fc): %d/%d/%d out_loaded: %zd, "
-//		"conv: %d, conv_total: %d\n", *fc->input_eof,
-//		fc->output_eof? *fc->output_eof : -42,
-//		fc->eof, *fc->out_loaded, conv, conv_total);
 	if (conv)
 		goto again;
+	if (conv_total) {
+		/*
+		 * Other pre_select functions might have already been called by
+		 * now and decided to do nothing, e.g. because their output
+		 * buffer was full or the input buffer was empty. We just
+		 * converted something which caused these buffers to change but
+		 * we can't make the other tasks reconsider their decision at
+		 * this point.  So force a minimal timeout for the next select
+		 * call to avoid unnecessary delays.
+		 */
+		s->timeout.tv_sec = 0;
+		s->timeout.tv_usec = 1;
+	}
 	if (*fc->input_error >= 0)
 		return;
 	if (*fc->out_loaded)
-- 
2.39.5