Module Name: src
Committed By: pgoyette
Date: Sun Jul 17 02:37:54 UTC 2016
Modified Files:
src/sys/kern [pgoyette-localcount]: subr_devsw.c
Log Message:
More locking fixes from riastradh@
To generate a diff of this commit:
cvs rdiff -u -r1.34.2.2 -r1.34.2.3 src/sys/kern/subr_devsw.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/kern/subr_devsw.c
diff -u src/sys/kern/subr_devsw.c:1.34.2.2 src/sys/kern/subr_devsw.c:1.34.2.3
--- src/sys/kern/subr_devsw.c:1.34.2.2 Sat Jul 16 22:35:34 2016
+++ src/sys/kern/subr_devsw.c Sun Jul 17 02:37:54 2016
@@ -1,4 +1,4 @@
-/* $NetBSD: subr_devsw.c,v 1.34.2.2 2016/07/16 22:35:34 pgoyette Exp $ */
+/* $NetBSD: subr_devsw.c,v 1.34.2.3 2016/07/17 02:37:54 pgoyette Exp $ */
/*-
* Copyright (c) 2001, 2002, 2007, 2008 The NetBSD Foundation, Inc.
@@ -69,7 +69,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_devsw.c,v 1.34.2.2 2016/07/16 22:35:34 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_devsw.c,v 1.34.2.3 2016/07/17 02:37:54 pgoyette Exp $");
#ifdef _KERNEL_OPT
#include "opt_dtrace.h"
@@ -113,6 +113,7 @@ static void devsw_detach_locked(const st
kmutex_t device_lock;
kcondvar_t device_cv;
+pserialize_t device_psz;
void (*biodone_vfs)(buf_t *) = (void *)nullop;
@@ -124,6 +125,7 @@ devsw_init(void)
KASSERT(sys_cdevsws < MAXDEVSW - 1);
mutex_init(&device_lock, MUTEX_DEFAULT, IPL_NONE);
cv_init(&device_cv, "devsw");
+ device_psz = pserialize_init();
}
int
@@ -359,7 +361,7 @@ cdevsw_attach(const struct cdevsw *devsw
static void
devsw_detach_locked(const struct bdevsw *bdev, const struct cdevsw *cdev)
{
- int i, j, s;
+ int i, j;
KASSERT(mutex_owned(&device_lock));
@@ -390,7 +392,15 @@ devsw_detach_locked(const struct bdevsw
if (j < max_cdevsws )
cdevsw[j] = NULL;
- s = pserialize_read_enter();
+ /* We need to wait for all current readers to finish. */
+ pserialize_perform(device_psz);
+
+ /*
+ * Here, no new readers can reach the bdev and cdev via the
+ * {b,c}devsw[] arrays. Wait for existing references to
+ * drain, and then destroy.
+ */
+
if (i < max_bdevsws && bdev->d_localcount != NULL) {
localcount_drain(bdev->d_localcount, &device_cv, &device_lock);
localcount_fini(bdev->d_localcount);
@@ -399,7 +409,6 @@ devsw_detach_locked(const struct bdevsw
localcount_drain(cdev->d_localcount, &device_cv, &device_lock);
localcount_fini(cdev->d_localcount);
}
- pserialize_read_exit(s);
}
int
@@ -444,9 +453,6 @@ bdevsw_lookup_acquire(dev_t dev)
if (bmajor < 0 || bmajor >= max_bdevsws)
return (NULL);
- /* Prevent any concurrent attempts to detach the device */
- mutex_enter(&device_lock);
-
/* Start a read transaction to block localcount_drain() */
s = pserialize_read_enter();
@@ -463,9 +469,6 @@ bdevsw_lookup_acquire(dev_t dev)
localcount_acquire(bdevsw[bmajor]->d_localcount);
out: pserialize_read_exit(s);
- mutex_exit(&device_lock);
-
- return bdev;
}
void
