Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763271AbdLSN5k (ORCPT ); Tue, 19 Dec 2017 08:57:40 -0500 Received: from mail-pg0-f65.google.com ([74.125.83.65]:40042 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763240AbdLSN5d (ORCPT ); Tue, 19 Dec 2017 08:57:33 -0500 X-Google-Smtp-Source: ACJfBot99xE9m7+NihDjyhjaMmw8BeQm7w+esRyobEwPVZpskUMNKV21afT0Rcle+BDBpFwyAohorA== Subject: Re: [PATCH V2 1/2] bdisp: Fix a possible sleep-in-atomic bug in bdisp_hw_reset To: Fabien DESSENNE , "hverkuil@xs4all.nl" , Benjamin GAIGNARD , "mchehab@kernel.org" Cc: "linux-media@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <1513425251-4143-1-git-send-email-baijiaju1990@gmail.com> From: Jia-Ju Bai Message-ID: <0551d83c-47c6-e3e0-77fd-f861c6878cbe@gmail.com> Date: Tue, 19 Dec 2017 21:57:15 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2236 Lines: 81 On 2017/12/19 18:43, Fabien DESSENNE wrote: > Hi, > > > On 16/12/17 12:54, Jia-Ju Bai wrote: >> The driver may sleep under a spinlock. >> The function call path is: >> bdisp_device_run (acquire the spinlock) >> bdisp_hw_reset >> msleep --> may sleep >> >> To fix it, readl_poll_timeout_atomic is used to replace msleep. >> >> This bug is found by my static analysis tool(DSAC) and >> checked by my code review. >> >> Signed-off-by: Jia-Ju Bai >> --- >> drivers/media/platform/sti/bdisp/bdisp-hw.c | 16 ++++++++-------- >> 1 file changed, 8 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/media/platform/sti/bdisp/bdisp-hw.c b/drivers/media/platform/sti/bdisp/bdisp-hw.c >> index b7892f3..e94a371 100644 >> --- a/drivers/media/platform/sti/bdisp/bdisp-hw.c >> +++ b/drivers/media/platform/sti/bdisp/bdisp-hw.c >> @@ -5,6 +5,7 @@ >> */ >> >> #include > This delay.h include is no more needed, remove it. > >> +#include >> >> #include "bdisp.h" >> #include "bdisp-filter.h" >> @@ -366,7 +367,7 @@ struct bdisp_filter_addr { >> */ >> int bdisp_hw_reset(struct bdisp_dev *bdisp) >> { >> - unsigned int i; >> + u32 tmp; >> >> dev_dbg(bdisp->dev, "%s\n", __func__); >> >> @@ -379,15 +380,14 @@ int bdisp_hw_reset(struct bdisp_dev *bdisp) >> writel(0, bdisp->regs + BLT_CTL); >> >> /* Wait for reset done */ >> - for (i = 0; i < POLL_RST_MAX; i++) { >> - if (readl(bdisp->regs + BLT_STA1) & BLT_STA1_IDLE) >> - break; >> - msleep(POLL_RST_DELAY_MS); >> - } >> - if (i == POLL_RST_MAX) > As recommended by Mauro, please add this comment: > Despite the large timeout, most of the time the reset happens without > needing any delays > >> + if (readl_poll_timeout_atomic(bdisp->regs + BLT_STA1, tmp, >> + (tmp & BLT_STA1_IDLE), POLL_RST_DELAY_MS, >> + POLL_RST_DELAY_MS * POLL_RST_MAX)) { > read_poll_timeout expects US timings, not MS. > >> dev_err(bdisp->dev, "Reset timeout\n"); >> + return -EAGAIN; >> + } >> >> - return (i == POLL_RST_MAX) ? -EAGAIN : 0; >> + return 0; >> } >> >> /** Hi, Okay, I have submitted a new patch according to your advice :) Thanks, Jia-Ju Bai