From 65bb956e5eb921bbe7b1c4beed18979d7c725703 Mon Sep 17 00:00:00 2001
From: spiriou <simon.piriou@korys.io>
Date: Mon, 21 Sep 2020 11:41:20 +0200
Subject: [PATCH] pipe: check for writers first in case of pipe empty

---
 drivers/pipes/pipe_common.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/pipes/pipe_common.c b/drivers/pipes/pipe_common.c
index e21f169943..0bf6095eb3 100644
--- a/drivers/pipes/pipe_common.c
+++ b/drivers/pipes/pipe_common.c
@@ -426,14 +426,6 @@ ssize_t pipecommon_read(FAR struct file *filep, FAR char *buffer, size_t len)
 
   while (dev->d_wrndx == dev->d_rdndx)
     {
-      /* If O_NONBLOCK was set, then return EGAIN */
-
-      if (filep->f_oflags & O_NONBLOCK)
-        {
-          nxsem_post(&dev->d_bfsem);
-          return -EAGAIN;
-        }
-
       /* If there are no writers on the pipe, then return end of file */
 
       if (dev->d_nwriters <= 0)
@@ -442,6 +434,14 @@ ssize_t pipecommon_read(FAR struct file *filep, FAR char *buffer, size_t len)
           return 0;
         }
 
+      /* If O_NONBLOCK was set, then return EGAIN */
+
+      if (filep->f_oflags & O_NONBLOCK)
+        {
+          nxsem_post(&dev->d_bfsem);
+          return -EAGAIN;
+        }
+
       /* Otherwise, wait for something to be written to the pipe */
 
       sched_lock();