igb_avb: patch for Realtime systems which require Priority inheritence
Posted by Anonymous on Thu 12th Oct 2023 10:54
raw | new post
modification of post by Anonymous (view diff)

From e8ca16ec8ac0259c7d60bdb4a181995b7a5f3d61 Mon Sep 17 00:00:00 2001
From: Roland Mainz <roland.mainz@nrubsig.org>
Date: Thu, 12 Oct 2023 11:42:20 +0200
Subject: [PATCH] libigb: Use PTHREAD_PRIO_INHERIT for mutex to avoid realtime
 issues

libigb: Use the |PTHREAD_PRIO_INHERIT| thread priority inheritence
protocol for the POSIX mutex to avoid realtime issues where one
lower-priority thread can stall a higher-priority RT thread.

Seen in real-life with our SERCOS software.

Reviewed-by: Siegfried Wulsch <siegfried.wulsch@rovema.de>
Signed-off-by: Marvin Wenzel <marvin.wenzel@rovema.de>
---
 lib/igb.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/igb.c b/lib/igb.c
index 00a3560..647234f 100644
--- a/lib/igb.c
+++ b/lib/igb.c
@@ -2562,6 +2562,14 @@ static int igb_create_lock(struct adapter *adapter)

                attr_allocated = true;

+#if ((_POSIX_THREAD_ROBUST_PRIO_INHERIT-0) < 200809L)
+/* Protect against libc implementations which do not support this */
+#error Priority inheritence not supported for robust mutexes with this pthread implementation
+#endif
+               // realtime applications usually require priority inheritence
+               if (pthread_mutexattr_setprotocol(&attr, PTHREAD_PRIO_INHERIT) != 0)
+                       goto err;
+
                // to be used for both inter-process and inter-thread synchronization
                if (pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED) != 0)
                        goto err;
--
2.30.2