Module Name: src
Committed By: riastradh
Date: Tue Sep 7 10:43:51 UTC 2021
Modified Files:
src/sys/dev/usb: ugen.c
Log Message:
ugen(4): Use cv_wait loop for draining reference count on detach.
- Should be no need to use cv_timedwait because all users have now
been given a wakeup (previously writers were not, so we relied on
the timeouts to work out).
- Need to run this in a loop or else a spurious wakeup could cause us
to free data structures before the users have actually drained.
To generate a diff of this commit:
cvs rdiff -u -r1.165 -r1.166 src/sys/dev/usb/ugen.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/dev/usb/ugen.c
diff -u src/sys/dev/usb/ugen.c:1.165 src/sys/dev/usb/ugen.c:1.166
--- src/sys/dev/usb/ugen.c:1.165 Tue Sep 7 10:43:34 2021
+++ src/sys/dev/usb/ugen.c Tue Sep 7 10:43:51 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: ugen.c,v 1.165 2021/09/07 10:43:34 riastradh Exp $ */
+/* $NetBSD: ugen.c,v 1.166 2021/09/07 10:43:51 riastradh Exp $ */
/*
* Copyright (c) 1998, 2004 The NetBSD Foundation, Inc.
@@ -37,7 +37,7 @@
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ugen.c,v 1.165 2021/09/07 10:43:34 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ugen.c,v 1.166 2021/09/07 10:43:51 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_compat_netbsd.h"
@@ -1215,6 +1215,12 @@ ugen_detach(device_t self, int flags)
}
}
+ /*
+ * Wait for users to drain. Before this point there can be no
+ * more I/O operations started because we set sc_dying; after
+ * this, there can be no more I/O operations in progress, so it
+ * will be safe to free things.
+ */
mutex_enter(&sc->sc_lock);
if (--sc->sc_refcnt >= 0) {
/* Wake everyone */
@@ -1223,8 +1229,9 @@ ugen_detach(device_t self, int flags)
cv_broadcast(&sc->sc_endpoints[i][dir].cv);
}
/* Wait for processes to go away. */
- if (cv_timedwait(&sc->sc_detach_cv, &sc->sc_lock, hz * 60))
- aprint_error_dev(self, ": didn't detach\n");
+ do {
+ cv_wait(&sc->sc_detach_cv, &sc->sc_lock);
+ } while (sc->sc_refcnt >= 0);
}
mutex_exit(&sc->sc_lock);
