Author: trasz
Date: Sat Aug 23 11:38:31 2014
New Revision: 270399
URL: http://svnweb.freebsd.org/changeset/base/270399
Log:
Add comment explaining one of the quirks in autofs.
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Modified:
head/sys/fs/autofs/autofs.c
Modified: head/sys/fs/autofs/autofs.c
==============================================================================
--- head/sys/fs/autofs/autofs.c Sat Aug 23 11:34:56 2014 (r270398)
+++ head/sys/fs/autofs/autofs.c Sat Aug 23 11:38:31 2014 (r270399)
@@ -595,6 +595,14 @@ autofs_open(struct cdev *dev, int flags,
{
sx_xlock(&sc->sc_lock);
+ /*
+ * We must never block automountd(8) and its descendants, and we use
+ * session ID to determine that: we store session id of the process
+ * that opened the device, and then compare it with session ids
+ * of triggering processes. This means running a second automountd(8)
+ * instance would break the previous one. The check below prevents
+ * it from happening.
+ */
if (sc->sc_dev_opened) {
sx_xunlock(&sc->sc_lock);
return (EBUSY);
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