From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: [PATCH -rt] Fix kmap_high_get() Date: Fri, 14 Aug 2009 16:02:53 +0200 Message-ID: <1250258573.5241.1581.camel@twins> References: <1249810600-21946-3-git-send-email-u.kleine-koenig@pengutronix.de> <1250199243-18677-1-git-send-email-u.kleine-koenig@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Thomas Gleixner , rt-users , Nicolas Pitre , MinChan Kim , Andrew Morton , Ingo Molnar , Li Zefan , Jens Axboe , linux-mm@kvack.org, linux-kernel@vger.kernel.org To: Uwe =?ISO-8859-1?Q?Kleine-K=F6nig?= Return-path: Received: from viefep11-int.chello.at ([62.179.121.31]:2943 "EHLO viefep11-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753959AbZHNODZ (ORCPT ); Fri, 14 Aug 2009 10:03:25 -0400 In-Reply-To: <1250199243-18677-1-git-send-email-u.kleine-koenig@pengutronix.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Thu, 2009-08-13 at 23:34 +0200, Uwe Kleine-K=C3=B6nig wrote: > This fixes the build failure with ARCH_NEEDS_KMAP_HIGH_GET. > This is only compile tested. >=20 > Signed-off-by: Uwe Kleine-K=C3=B6nig > Cc: Nicolas Pitre > Cc: MinChan Kim > Cc: Andrew Morton > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Thomas Gleixner > Cc: Li Zefan > Cc: Jens Axboe > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > Hello >=20 > this bases on the patch "[PATCH RT 9/6] [RFH] Build failure on > 2.6.31-rc4-rt1 in mm/highmem.c" earlier in this thread. >=20 > I don't know if kmap_high_get() has to call kmap_account(). Anyone? I think it should, since it uses kunmap_high() to undo whatever kmap_high_get() did. Now, if there'd been a kmap_high_put()... :-) As to the patch, its not quite right. >>From what I understand kmap_high_get() is used to pin a page's kmap if= f it has one, whereas the result of your patch seems to be that it'll actually create one if its not found. Something like the below ought to do I guess. Signed-off-by: Peter Zijlstra --- arch/arm/include/asm/highmem.h | 1 + arch/arm/mm/dma-mapping.c | 2 +- mm/highmem.c | 50 ++++++++++++++++++--------------= ------- 3 files changed, 25 insertions(+), 28 deletions(-) diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/high= mem.h index 7f36d00..4d9573b 100644 --- a/arch/arm/include/asm/highmem.h +++ b/arch/arm/include/asm/highmem.h @@ -19,6 +19,7 @@ extern pte_t *pkmap_page_table; =20 extern void *kmap_high(struct page *page); extern void *kmap_high_get(struct page *page); +extern void *kmap_high_put(struct page *page); extern void kunmap_high(struct page *page); =20 extern void *kmap(struct page *page); diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 1576176..4a166d9 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -551,7 +551,7 @@ static void dma_cache_maint_contiguous(struct page = *page, unsigned long offset, if (vaddr) { vaddr +=3D offset; inner_op(vaddr, vaddr + size); - kunmap_high(page); + kmap_high_put(page); } } =20 diff --git a/mm/highmem.c b/mm/highmem.c index 66e915a..b2eaefe 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -75,26 +75,6 @@ pte_t * pkmap_page_table; =20 static DECLARE_WAIT_QUEUE_HEAD(pkmap_wait); =20 - -/* - * Most architectures have no use for kmap_high_get(), so let's abstra= ct - * the disabling of IRQ out of the locking in that case to save on a - * potential useless overhead. - */ -#ifdef ARCH_NEEDS_KMAP_HIGH_GET -#define lock_kmap() spin_lock_irq(&kmap_lock) -#define unlock_kmap() spin_unlock_irq(&kmap_lock) -#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags) -#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, fla= gs) -#else -#define lock_kmap() spin_lock(&kmap_lock) -#define unlock_kmap() spin_unlock(&kmap_lock) -#define lock_kmap_any(flags) \ - do { spin_lock(&kmap_lock); (void)(flags); } while (0) -#define unlock_kmap_any(flags) \ - do { spin_unlock(&kmap_lock); (void)(flags); } while (0) -#endif - /* * Try to free a given kmap slot. * @@ -361,22 +341,38 @@ EXPORT_SYMBOL(kmap_high); * * Returns the page's current virtual memory address, or NULL if no ma= pping * exists. When and only when a non null address is returned then a - * matching call to kunmap_high() is necessary. + * matching call to kmap_high_put() is necessary. * * This can be called from any context. */ void *kmap_high_get(struct page *page) { - unsigned long vaddr, flags; + unsigned long vaddr; =20 - lock_kmap_any(flags); +again: vaddr =3D (unsigned long)page_address(page); if (vaddr) { - BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1); - pkmap_count[PKMAP_NR(vaddr)]++; + atomic_t *counter =3D &pkmap_count[PKMAP_NR(vaddr)]; + if (atomic_inc_not_zero(counter)) { + unsigned long vaddr2 =3D (unsigned long)page_address(page); + + if (likely(vaddr =3D=3D vaddr2)) + return (void *)vaddr; + + pkmap_put(counter); + goto again; + } } - unlock_kmap_any(flags); - return (void*) vaddr; + + return NULL; +} + +void kmap_high_put(struct page *page) +{ + unsigned long vaddr =3D (unsigned long)page_address(page); + + BUG_ON(!vaddr); + pkmap_put(&pkmap_count[PKMAP_NR(vaddr)]); } #endif =20 -- To unsubscribe from this list: send the line "unsubscribe linux-rt-user= s" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html