From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932425AbbCXRGD (ORCPT ); Tue, 24 Mar 2015 13:06:03 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33703 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933018AbbCXRF4 (ORCPT ); Tue, 24 Mar 2015 13:05:56 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexander Sverdlin , Mark Brown Subject: [PATCH 3.19 062/123] spi: pl022: Fix race in giveback() leading to driver lock-up Date: Tue, 24 Mar 2015 16:46:11 +0100 Message-Id: <20150324154426.864970532@linuxfoundation.org> X-Mailer: git-send-email 2.3.3 In-Reply-To: <20150324154423.655554012@linuxfoundation.org> References: <20150324154423.655554012@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexander Sverdlin commit cd6fa8d2ca53cac3226fdcffcf763be390abae32 upstream. Commit fd316941c ("spi/pl022: disable port when unused") introduced a race, which leads to possible driver lock up (easily reproducible on SMP). The problem happens in giveback() function where the completion of the transfer is signalled to SPI subsystem and then the HW SPI controller is disabled. Another transfer might be setup in between, which brings driver in locked-up state. Exact event sequence on SMP: core0 core1 => pump_transfers() /* message->state == STATE_DONE */ => giveback() => spi_finalize_current_message() => pl022_unprepare_transfer_hardware() => pl022_transfer_one_message => flush() => do_interrupt_dma_transfer() => set_up_next_transfer() /* Enable SSP, turn on interrupts */ writew((readw(SSP_CR1(pl022->virtbase)) | SSP_CR1_MASK_SSE), SSP_CR1(pl022->virtbase)); ... => pl022_interrupt_handler() => readwriter() /* disable the SPI/SSP operation */ => writew((readw(SSP_CR1(pl022->virtbase)) & (~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase)); Lockup! SPI controller is disabled and the data will never be received. Whole SPI subsystem is waiting for transfer ACK and blocked. So, only signal transfer completion after disabling the controller. Fixes: fd316941c (spi/pl022: disable port when unused) Signed-off-by: Alexander Sverdlin Signed-off-by: Mark Brown Signed-off-by: Greg Kroah-Hartman --- drivers/spi/spi-pl022.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/spi/spi-pl022.c +++ b/drivers/spi/spi-pl022.c @@ -534,12 +534,12 @@ static void giveback(struct pl022 *pl022 pl022->cur_msg = NULL; pl022->cur_transfer = NULL; pl022->cur_chip = NULL; - spi_finalize_current_message(pl022->master); /* disable the SPI/SSP operation */ writew((readw(SSP_CR1(pl022->virtbase)) & (~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase)); + spi_finalize_current_message(pl022->master); } /**