Module Name: src
Committed By: riastradh
Date: Sun Dec 19 11:21:20 UTC 2021
Modified Files:
src/sys/external/bsd/drm2/linux: linux_ww_mutex.c
Log Message:
linux/ww_mutex: Disable locking-against-self asserts in trylock.
This seems to be done intentionally in Linux.
To generate a diff of this commit:
cvs rdiff -u -r1.8 -r1.9 src/sys/external/bsd/drm2/linux/linux_ww_mutex.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/external/bsd/drm2/linux/linux_ww_mutex.c
diff -u src/sys/external/bsd/drm2/linux/linux_ww_mutex.c:1.8 src/sys/external/bsd/drm2/linux/linux_ww_mutex.c:1.9
--- src/sys/external/bsd/drm2/linux/linux_ww_mutex.c:1.8 Sun Dec 19 10:38:14 2021
+++ src/sys/external/bsd/drm2/linux/linux_ww_mutex.c Sun Dec 19 11:21:20 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: linux_ww_mutex.c,v 1.8 2021/12/19 10:38:14 riastradh Exp $ */
+/* $NetBSD: linux_ww_mutex.c,v 1.9 2021/12/19 11:21:20 riastradh Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_ww_mutex.c,v 1.8 2021/12/19 10:38:14 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_ww_mutex.c,v 1.9 2021/12/19 11:21:20 riastradh Exp $");
#include <sys/types.h>
#include <sys/atomic.h>
@@ -760,12 +760,27 @@ ww_mutex_trylock(struct ww_mutex *mutex)
WW_LOCKED(mutex);
ret = 1;
} else {
+ /*
+ * It is tempting to assert that we do not hold the
+ * mutex here, because trylock when we hold the lock
+ * already generally indicates a bug in the design of
+ * the code. However, it seems that Linux relies on
+ * this deep in ttm buffer reservation logic, so these
+ * assertions are disabled until we find another way to
+ * work around that or fix the bug that leads to it.
+ *
+ * That said: we should not be in the WW_WANTOWN state,
+ * which happens only while we're in the ww mutex logic
+ * waiting to acquire the lock.
+ */
+#if 0
KASSERTMSG(((mutex->wwm_state != WW_OWNED) ||
(mutex->wwm_u.owner != curlwp)),
"locking %p against myself: %p", mutex, curlwp);
KASSERTMSG(((mutex->wwm_state != WW_CTX) ||
(mutex->wwm_u.ctx->wwx_owner != curlwp)),
"locking %p against myself: %p", mutex, curlwp);
+#endif
KASSERTMSG(((mutex->wwm_state != WW_WANTOWN) ||
(mutex->wwm_u.ctx->wwx_owner != curlwp)),
"locking %p against myself: %p", mutex, curlwp);
