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authorriastradh <riastradh@NetBSD.org>2022-08-22 00:19:12 +0000
committerriastradh <riastradh@NetBSD.org>2022-08-22 00:19:12 +0000
commit639e3bb52914d4db63014cd38eb63018cdddb9db (patch)
tree411749a6651b03d77832bc72f30fe0cb22fb7638 /sys/dev
parent6778c43f7397884475ce0fc52f2a19f4ab3b5265 (diff)
dk(4): Serialize closing parent's dk_rawvp with opening it.
Otherwise, the following events might happen: - process 123 had /dev/rdkN open, starts close, enters dk_close_parent - process 456 opens /dev/rdkM (same parent, different wedge), calls dk_open_parent At this point, the block device hasn't yet closed, so dk_open_parent will fail with EBUSY. This is incorrect -- the chardev is never supposed to fail with EBUSY, and dkopen/dkclose carefully manage state to avoid opening the block device while it's still open. The problem is that dkopen in process 456 didn't wait for vn_close in process 123 to finish before calling VOP_OPEN. (Note: If it were the _same_ chardev /dev/rdkN in both processes, then spec_open/close would prevent this. But since it's a _different_ chardev, spec_open/close assume that concurrency is OK, and it's the driver's responsibility to serialize access to the parent disk which, unbeknownst to spec_open/close, is shared between dkN and dkM.) It appears that the vn_close call was previously moved outside dk_rawlock in 2010 to work around an unrelated bug in raidframe that had already been fixed in HEAD: Crash pointing to dk_rawlock and raidclose: https://mail-index.netbsd.org/tech-kern/2010/07/27/msg008612.html Change working around that crash: https://mail-index.netbsd.org/source-changes/2010/08/04/msg012270.html Change removing raidclose -> mutex_destroy(&dk_rawlock) path: https://mail-index.netbsd.org/source-changes/2009/07/23/msg223381.html
Diffstat (limited to 'sys/dev')
-rw-r--r--sys/dev/dkwedge/dk.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/sys/dev/dkwedge/dk.c b/sys/dev/dkwedge/dk.c
index 97430e76da1..9379ebadf9e 100644
--- a/sys/dev/dkwedge/dk.c
+++ b/sys/dev/dkwedge/dk.c
@@ -1,4 +1,4 @@
-/* $NetBSD: dk.c,v 1.112 2022/06/11 18:17:00 martin Exp $ */
+/* $NetBSD: dk.c,v 1.113 2022/08/22 00:19:12 riastradh Exp $ */
/*-
* Copyright (c) 2004, 2005, 2006, 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: dk.c,v 1.112 2022/06/11 18:17:00 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dk.c,v 1.113 2022/08/22 00:19:12 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_dkwedge.h"
@@ -1220,13 +1220,13 @@ dklastclose(struct dkwedge_softc *sc)
}
}
- mutex_exit(&sc->sc_parent->dk_rawlock);
- mutex_exit(&sc->sc_dk.dk_openlock);
-
if (vp) {
dk_close_parent(vp, mode);
}
+ mutex_exit(&sc->sc_parent->dk_rawlock);
+ mutex_exit(&sc->sc_dk.dk_openlock);
+
return error;
}