[src/pgoyette-localcount]: src/sys/kern Defer initialization of the pserializ...

[pgoyette <pgoyette%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b7044e1a5d0c
branches:  pgoyette-localcount
changeset: 852801:b7044e1a5d0c
user:      pgoyette <pgoyette%NetBSD.org@localhost>
date:      Sun Jul 17 05:02:19 2016 +0000

description:
Defer initialization of the pserialize_t device_psz" until just before
we need it.  We can't initialize within devsw_init() because init_main()
has not yet initialized the pserialize stuff.

Restore a "return bdev" in bdevsw_lookup_acquire() - accidental deletion

Update cdevsw_lookup_acquire() to match bdev_lookup_acquire()

diffstat:

 sys/kern/subr_devsw.c |  21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diffs (77 lines):

diff -r 734a8f084f72 -r b7044e1a5d0c sys/kern/subr_devsw.c
--- a/sys/kern/subr_devsw.c     Sun Jul 17 02:44:41 2016 +0000
+++ b/sys/kern/subr_devsw.c     Sun Jul 17 05:02:19 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_devsw.c,v 1.34.2.3 2016/07/17 02:37:54 pgoyette Exp $     */
+/*     $NetBSD: subr_devsw.c,v 1.34.2.4 2016/07/17 05:02:19 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 1.34.2.3 2016/07/17 02:37:54 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_devsw.c,v 1.34.2.4 2016/07/17 05:02:19 pgoyette Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_dtrace.h"
@@ -113,7 +113,7 @@
 
 kmutex_t       device_lock;
 kcondvar_t     device_cv;
-pserialize_t   device_psz;
+pserialize_t   device_psz = NULL;
 
 void (*biodone_vfs)(buf_t *) = (void *)nullop;
 
@@ -125,7 +125,6 @@
        KASSERT(sys_cdevsws < MAXDEVSW - 1);
        mutex_init(&device_lock, MUTEX_DEFAULT, IPL_NONE);
        cv_init(&device_cv, "devsw");
-       device_psz = pserialize_init();
 }
 
 int
@@ -392,7 +391,12 @@
        if (j < max_cdevsws )
                cdevsw[j] = NULL;
 
-       /* We need to wait for all current readers to finish. */
+       /*
+        * If we haven't already done so, create the serialization
+        * stucture.  Then wait for all current readers to finish.
+        */
+       if(__predict_false(device_psz == NULL))
+               device_psz = pserialize_create();
        pserialize_perform(device_psz);
 
        /*
@@ -469,6 +473,8 @@
                localcount_acquire(bdevsw[bmajor]->d_localcount);
 
 out:   pserialize_read_exit(s);
+
+       return bdev;
 }
 
 void
@@ -512,9 +518,6 @@
        if (cmajor < 0 || cmajor >= max_cdevsws)
                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();
 
@@ -523,7 +526,7 @@
        if (cdev == NULL)
                goto out;
 
-       /* Wait for the content of the struct bdevsw to become visible */
+       /* Wait for the content of the struct cdevsw to become visible */
        membar_datadep_consumer();
 
        /* If the devsw is not statically linked, acquire a reference */