kern/161887: panic at vm_page_wire with FreeBSD 9.0 Beta 3

[Penta Upa]

>Number:         161887
>Category:       kern
>Synopsis:       panic at vm_page_wire with FreeBSD 9.0 Beta 3
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Oct 21 18:10:10 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Penta Upa
>Release:        FreeBSD 9.0 Beta 3
>Organization:
>Environment:
FreeBSD scache 9.0-BETA3 FreeBSD 9.0-BETA3 #0: Sat Sep 24 21:31:28 UTC 2011     
root at farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

>Description:
External modules calling vm_page_wire() even after calling vm_page_lock() results in the following assertion failure in vm_page.c
panic: mutex page lock not owned at /usr/src/sys/vm/vm_page:1845

Interestingly check for vm page locked is also done in the external module but there is no assertion there. More clearly within the external module

vm_page_lock(pp);
vm_page_lock_assert(pp, MA_OWNED); /* No panic here */
vm_page_wire(pp); /* Panic here for the same assertion as above, strange */
vm_page_unlock(pp);

The machine in use is a fresh install of FreeBSD 9 Beta 3. No changes to the kernel were made. Problem however exists ever after a kernel recompile.

I have also sent a mail to the mailing list on this. http://lists.freebsd.org/pipermail/freebsd-current/2011-October/028550.html

I dont have a backtrace of the crash as i'm unable to configure kernel dumps yet. Will post them once i have it.
>How-To-Repeat:
Try the attached vmtest.c

Makefile contents are

KMOD    =  vmtest

SRCS    =  vmtest.c

.include <bsd.kmod.mk>

>Fix:


Patch attached with submission follows:

#include <sys/param.h>
#include <sys/module.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/time.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/mutex.h>


#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_object.h>

static void
vmtest(void) {
	vm_page_t pp;

	pp = vm_page_alloc(NULL, 0, VM_ALLOC_NOOBJ | VM_ALLOC_NORMAL);
	if (!pp) {
		printf("Page allocation failure\n");
		return;
	}
	vm_page_lock(pp);
	vm_page_lock_assert(pp, MA_OWNED);
	vm_page_wire(pp);
	vm_page_unlock(pp);
}

/* The function called at load/unload. */
static int event_handler(struct module *module, int event, void *arg) {
	switch (event) {
	case MOD_LOAD:
		vmtest();
		break;
	case MOD_UNLOAD:
		break;
	default:
		break;
	}
	return 0;
}

static moduledata_t vmtest_conf = {
    "vmtest",
     event_handler,
     NULL
};

DECLARE_MODULE(vmtest, vmtest_conf, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);


>Release-Note:
>Audit-Trail:
>Unformatted: