Date: Sat, 08 Sep 2012 12:51:58 -0500 From: Alan Cox <alc@rice.edu> To: Ian Lepore <freebsd@damnhippie.dyndns.org> Cc: "arm@freebsd.org" <arm@freebsd.org>, Alan Cox <alc@rice.edu> Subject: Re: arm pmap locking Message-ID: <504B85BE.3030101@rice.edu> In-Reply-To: <1346723041.1140.602.camel@revolution.hippie.lan> References: <502FD67A.7030003@rice.edu> <1345315508.27688.260.camel@revolution.hippie.lan> <503D12AE.1050705@rice.edu> <1346350374.1140.525.camel@revolution.hippie.lan> <5045351F.6060201@rice.edu> <1346723041.1140.602.camel@revolution.hippie.lan>
next in thread | previous in thread | raw e-mail | index | archive | help
This is a multi-part message in MIME format.
--------------090708090103090700060808
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
On 09/03/2012 20:44, Ian Lepore wrote:
> On Mon, 2012-09-03 at 17:54 -0500, Alan Cox wrote:
>> On 08/30/2012 13:12, Ian Lepore wrote:
>>> On Tue, 2012-08-28 at 13:49 -0500, Alan Cox wrote:
>>>> Can you please retry with the attached patch? For the time being, I
>>>> decided to address the above problem by simply enabling recursion on the
>>>> new pmap lock. As I mentioned in my prior message, the lock recursion
>>>> in the arm pmap is a mistake. However, I'd rather not change two things
>>>> at once, i.e., replace the page queues lock and fix the lock recursion.
>>>> I'll take a look at eliminating the lock recursion later this week.
>>>>
>>>> Thanks,
>>>> Alan
>>>>
>>> Sorry for the delay, I finally got around to trying this today, and it
>>> seems to be working well initially -- it boots to multiuser and the only
>>> difference in the dmesg.boot with and without the patch is the compile
>>> date, and the kernel image is 128 bytes smaller with the patch. I've
>>> got DIAGNOSTIC and INVARIANTS enabled; I'll run with the patch in place
>>> and let you know if anything glitches.
>>>
>> Could you please test the attached patch? This is a small step toward
>> disentangling the arm pmap locking.
>>
>> Alan
>>
> Applied the patch, it's running just fine.
>
Here is another patch. This simplifies the kernel pmap locking in
pmap_enter_pv() and corrects some comments.
Thanks in advance,
Alan
--------------090708090103090700060808
Content-Type: text/plain;
name="arm_pmap13.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
filename="arm_pmap13.patch"
Index: arm/arm/pmap.c
===================================================================
--- arm/arm/pmap.c (revision 240166)
+++ arm/arm/pmap.c (working copy)
@@ -1588,11 +1588,11 @@ pmap_clearbit(struct vm_page *pg, u_int maskbits)
*/
/*
- * pmap_enter_pv: enter a mapping onto a vm_page lst
+ * pmap_enter_pv: enter a mapping onto a vm_page's PV list
*
* => caller should hold the proper lock on pvh_global_lock
* => caller should have pmap locked
- * => we will gain the lock on the vm_page and allocate the new pv_entry
+ * => we will (someday) gain the lock on the vm_page's PV list
* => caller should adjust ptp's wire_count before calling
* => caller should not adjust pmap's wire_count
*/
@@ -1600,33 +1600,26 @@ static void
pmap_enter_pv(struct vm_page *pg, struct pv_entry *pve, pmap_t pm,
vm_offset_t va, u_int flags)
{
- int km;
rw_assert(&pvh_global_lock, RA_WLOCKED);
-
+ PMAP_ASSERT_LOCKED(pm);
if (pg->md.pv_kva != 0) {
- /* PMAP_ASSERT_LOCKED(pmap_kernel()); */
- pve->pv_pmap = pmap_kernel();
+ pve->pv_pmap = kernel_pmap;
pve->pv_va = pg->md.pv_kva;
pve->pv_flags = PVF_WRITE | PVF_UNMAN;
+ if (pm != kernel_pmap)
+ PMAP_LOCK(kernel_pmap);
+ TAILQ_INSERT_HEAD(&pg->md.pv_list, pve, pv_list);
+ TAILQ_INSERT_HEAD(&kernel_pmap->pm_pvlist, pve, pv_plist);
+ if (pm != kernel_pmap)
+ PMAP_UNLOCK(kernel_pmap);
pg->md.pv_kva = 0;
-
- if (!(km = PMAP_OWNED(pmap_kernel())))
- PMAP_LOCK(pmap_kernel());
- TAILQ_INSERT_HEAD(&pg->md.pv_list, pve, pv_list);
- TAILQ_INSERT_HEAD(&pve->pv_pmap->pm_pvlist, pve, pv_plist);
- PMAP_UNLOCK(pmap_kernel());
if ((pve = pmap_get_pv_entry()) == NULL)
panic("pmap_kenter_pv: no pv entries");
- if (km)
- PMAP_LOCK(pmap_kernel());
}
-
- PMAP_ASSERT_LOCKED(pm);
pve->pv_pmap = pm;
pve->pv_va = va;
pve->pv_flags = flags;
-
TAILQ_INSERT_HEAD(&pg->md.pv_list, pve, pv_list);
TAILQ_INSERT_HEAD(&pm->pm_pvlist, pve, pv_plist);
pg->md.pvh_attrs |= flags & (PVF_REF | PVF_MOD);
--------------090708090103090700060808--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?504B85BE.3030101>