From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967043AbdDZTgY (ORCPT ); Wed, 26 Apr 2017 15:36:24 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:34296 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753944AbdDZTgP (ORCPT ); Wed, 26 Apr 2017 15:36:15 -0400 Subject: Re: [PATCH] [media] s5p-jpeg: fix recursive spinlock acquisition To: Alexandre Courbot References: <20170425061943.717-1-acourbot@chromium.org> <14d0d257-a5c3-222e-137d-4991482c6fb4@gmail.com> Cc: Andrzej Pietrasiewicz , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org From: Jacek Anaszewski X-Enigmail-Draft-Status: N1110 Message-ID: Date: Wed, 26 Apr 2017 21:35:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/26/2017 04:54 AM, Alexandre Courbot wrote: > On Wed, Apr 26, 2017 at 4:15 AM, Jacek Anaszewski > wrote: >> Hi Alexandre, >> >> Thanks for the patch. >> >> On 04/25/2017 08:19 AM, Alexandre Courbot wrote: >>> v4l2_m2m_job_finish(), which is called from the interrupt handler with >>> slock acquired, can call the device_run() hook immediately if another >>> context was in the queue. This hook also acquires slock, resulting in >>> a deadlock for this scenario. >>> >>> Fix this by releasing slock right before calling v4l2_m2m_job_finish(). >>> This is safe to do as the state of the hardware cannot change before >>> v4l2_m2m_job_finish() is called anyway. >>> >>> Signed-off-by: Alexandre Courbot >>> --- >>> drivers/media/platform/s5p-jpeg/jpeg-core.c | 12 +++++++++--- >>> 1 file changed, 9 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/media/platform/s5p-jpeg/jpeg-core.c b/drivers/media/platform/s5p-jpeg/jpeg-core.c >>> index 52dc7941db65..223b4379929e 100644 >>> --- a/drivers/media/platform/s5p-jpeg/jpeg-core.c >>> +++ b/drivers/media/platform/s5p-jpeg/jpeg-core.c >>> @@ -2642,13 +2642,13 @@ static irqreturn_t s5p_jpeg_irq(int irq, void *dev_id) >>> if (curr_ctx->mode == S5P_JPEG_ENCODE) >>> vb2_set_plane_payload(&dst_buf->vb2_buf, 0, payload_size); >>> v4l2_m2m_buf_done(dst_buf, state); >>> - v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx); >>> >>> curr_ctx->subsampling = s5p_jpeg_get_subsampling_mode(jpeg->regs); >>> spin_unlock(&jpeg->slock); >>> >>> s5p_jpeg_clear_int(jpeg->regs); >>> >>> + v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx); >>> return IRQ_HANDLED; >>> } >>> >>> @@ -2707,11 +2707,12 @@ static irqreturn_t exynos4_jpeg_irq(int irq, void *priv) >>> v4l2_m2m_buf_done(dst_vb, VB2_BUF_STATE_ERROR); >>> } >>> >>> - v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx); >>> if (jpeg->variant->version == SJPEG_EXYNOS4) >>> curr_ctx->subsampling = exynos4_jpeg_get_frame_fmt(jpeg->regs); >>> >>> spin_unlock(&jpeg->slock); >>> + >>> + v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx); >>> return IRQ_HANDLED; >>> } >>> >>> @@ -2770,10 +2771,15 @@ static irqreturn_t exynos3250_jpeg_irq(int irq, void *dev_id) >>> if (curr_ctx->mode == S5P_JPEG_ENCODE) >>> vb2_set_plane_payload(&dst_buf->vb2_buf, 0, payload_size); >>> v4l2_m2m_buf_done(dst_buf, state); >>> - v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx); >>> >>> curr_ctx->subsampling = >>> exynos3250_jpeg_get_subsampling_mode(jpeg->regs); >>> + >>> + spin_unlock(&jpeg->slock); >>> + >>> + v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx); >>> + return IRQ_HANDLED; >>> + >>> exit_unlock: >>> spin_unlock(&jpeg->slock); >>> return IRQ_HANDLED; >>> >> >> Acked-by: Jacek Anaszewski >> >> Just out of curiosity - could you share how you discovered the problem - >> by some static checkers or trying to use the driver? > > We discovered this issue after adding a new unit test for the jpeg > codec in Chromium OS: > > https://bugs.chromium.org/p/chromium/issues/detail?id=705971 > >>>From what I understand the test spawns different processes that access > the codec device concurrently, creating the situation leading to the > bug. Thanks for the explanation. Nice fix. > On a slightly related note, I was thinking whether it would make sense > to move the call to v4l2_m2m_job_finish() (and maybe other parts of > the current interrupt handler) into a worker or a threaded interrupt > handler so as to reduce the time we spend with interrupts disabled. > Can I have your input on this idea? Right, all remaining drivers call it from workers. Feel free to submit a patch. -- Best regards, Jacek Anaszewski