Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751933AbaKIKxq (ORCPT ); Sun, 9 Nov 2014 05:53:46 -0500 Received: from mail-la0-f42.google.com ([209.85.215.42]:47602 "EHLO mail-la0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751431AbaKIKxm (ORCPT ); Sun, 9 Nov 2014 05:53:42 -0500 Subject: [PATCH v2] ACPI/osl: speedup grace period in acpi_os_map_cleanup From: Konstantin Khlebnikov To: linux-acpi@vger.kernel.org, "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Len Brown Cc: Tom Boshoven , "Paul E. McKenney" , x86@kernel.org, Josh Triplett , Alexander Monakov Date: Sun, 09 Nov 2014 13:53:37 +0400 Message-ID: <20141109105337.4952.36899.stgit@zurg> In-Reply-To: <20141108094717.9388.34638.stgit@zurg> References: <20141108094717.9388.34638.stgit@zurg> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ACPI maintains cache of ioremap regions to speed up operations and access to them from irq context where ioremap() calls aren't allowed. This code abuses synchronize_rcu() on unmap path for synchronization with fast-path in acpi_os_read/write_memory which uses this cache. Since v3.10 CPUs are allowed to enter idle state even if they have RCU callbacks queued, see commit c0f4dfd4f90f1667d234d21f15153ea09a2eaa66 ("rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks"). That change caused problems with nvidia proprietary driver which calls acpi_os_map/unmap_generic_address several times during initialization. Each unmap calls synchronize_rcu and adds significant delay. Totally initialization is slowed for a couple of seconds and that is enough to trigger timeout in hardware, gpu decides to "fell off the bus". Widely spread workaround is reducing "rcu_idle_gp_delay" from 4 to 1 jiffy. This patch replaces synchronize_rcu() with synchronize_rcu_expedited() which is much faster. Signed-off-by: Konstantin Khlebnikov Reported-and-tested-by: Alexander Monakov Cc: Tom Boshoven Link: https://devtalk.nvidia.com/default/topic/567297/linux/linux-3-10-driver-crash/ --- drivers/acpi/osl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index 9964f70..217713c 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -436,7 +436,7 @@ static void acpi_os_drop_map_ref(struct acpi_ioremap *map) static void acpi_os_map_cleanup(struct acpi_ioremap *map) { if (!map->refcount) { - synchronize_rcu(); + synchronize_rcu_expedited(); acpi_unmap(map->phys, map->virt); kfree(map); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/