Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932831AbbDGXUl (ORCPT ); Tue, 7 Apr 2015 19:20:41 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55723 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754437AbbDGWwj (ORCPT ); Tue, 7 Apr 2015 18:52:39 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Alexander Sverdlin , Mark Brown , Kamal Mostafa Subject: [PATCH 3.13.y-ckt 068/156] spi: pl022: Fix race in giveback() leading to driver lock-up Date: Tue, 7 Apr 2015 15:50:05 -0700 Message-Id: <1428447093-3282-69-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1428447093-3282-1-git-send-email-kamal@canonical.com> References: <1428447093-3282-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2861 Lines: 81 3.13.11-ckt19 -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: Kamal Mostafa --- drivers/spi/spi-pl022.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/spi/spi-pl022.c b/drivers/spi/spi-pl022.c index 971855e..fe091a8 100644 --- a/drivers/spi/spi-pl022.c +++ b/drivers/spi/spi-pl022.c @@ -503,12 +503,12 @@ 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); } /** -- 1.9.1 -- 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/