From 9628207066e1fc6d3666fdb085ba7c8bc75b94c7 Mon Sep 17 00:00:00 2001
From: Con Kolivas <kernel@kolivas.org>
Date: Mon, 9 Dec 2013 23:11:47 +1100
Subject: [PATCH] Provide a helper function that can reset cgsems to zero.

---
 util.c | 28 ++++++++++++++++++++++++++++
 util.h |  1 +
 2 files changed, 29 insertions(+)

diff --git a/util.c b/util.c
index 78cc7aaa..b5b1c762 100644
--- a/util.c
+++ b/util.c
@@ -2599,6 +2599,25 @@ int _cgsem_mswait(cgsem_t *cgsem, int ms, const char *file, const char *func, co
 	/* We don't reach here */
 	return 0;
 }
+
+/* Reset semaphore count back to zero */
+void cgsem_reset(cgsem_t *cgsem)
+{
+	int ret, fd;
+	fd_set rd;
+	char buf;
+
+	fd = cgsem->pipefd[0];
+	FD_ZERO(&rd);
+	FD_SET(fd, &rd);
+	do {
+		struct timeval timeout = {0, 0};
+
+		ret = select(fd + 1, &rd, NULL, NULL, &timeout);
+		if (ret > 0)
+			ret = read(fd, &buf, 1);
+	} while (ret > 0);
+}
 #else
 void _cgsem_init(cgsem_t *cgsem, const char *file, const char *func, const int line)
 {
@@ -2639,6 +2658,15 @@ int _cgsem_mswait(cgsem_t *cgsem, int ms, const char *file, const char *func, co
 	return 0;
 }
 
+void cgsem_reset(cgsem_t *cgsem)
+{
+	int ret;
+
+	do {
+		ret = sem_trywait(cgsem);
+	} while (!ret);
+}
+
 void cgsem_destroy(cgsem_t *cgsem)
 {
 	sem_destroy(cgsem);
diff --git a/util.h b/util.h
index d3596566..90b1ca90 100644
--- a/util.h
+++ b/util.h
@@ -138,6 +138,7 @@ void _cgsem_init(cgsem_t *cgsem, const char *file, const char *func, const int l
 void _cgsem_post(cgsem_t *cgsem, const char *file, const char *func, const int line);
 void _cgsem_wait(cgsem_t *cgsem, const char *file, const char *func, const int line);
 int _cgsem_mswait(cgsem_t *cgsem, int ms, const char *file, const char *func, const int line);
+void cgsem_reset(cgsem_t *cgsem);
 void cgsem_destroy(cgsem_t *cgsem);
 bool cg_completion_timeout(void *fn, void *fnarg, int timeout);