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([2402:f000:1:1501:200:5efe:a66f:470f]) by smtp.gmail.com with ESMTPSA id 1-v6sm9220229pfm.145.2018.08.29.19.34.22 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Aug 2018 19:34:24 -0700 (PDT) From: Jia-Ju Bai To: broonie@kernel.org, gregkh@linuxfoundation.org, rafael@kernel.org, David Howells , Dan Carpenter , Linus Torvalds , linus.walleij@linaro.org Cc: Linux Kernel Mailing List Subject: [BUG] [Resend] Possible sleep-in-atomic-context bugs involving regmap_lock_mutex() Message-ID: <9bcef57b-1a5c-cd16-8e44-932ef3be08cb@gmail.com> Date: Thu, 30 Aug 2018 10:34:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, My static tool DSAC reports many sleep-in-atomic-context bugs involving regmap_lock_mutex(), so I wonder whether this function is possible to be executed in atomic context. Here are some example bugs and their call paths in Linux-4.16 (from bottom to top, and [FUNC_PTR] means that there is a function pointer call): [FUNC] mutex_lock_nested drivers/base/regmap/regmap.c, 468: mutex_lock_nested in regmap_lock_mutex drivers/base/regmap/regmap.c, 2503: [FUNC_PTR]regmap_lock_mutex in regmap_read drivers/clk/clk-aspeed.c, 215: regmap_read in aspeed_clk_is_enabled drivers/clk/clk-aspeed.c, 230: aspeed_clk_is_enabled in aspeed_clk_enable drivers/clk/clk-aspeed.c, 228: _raw_spin_lock_irqsave in aspeed_clk_enable [FUNC] mutex_lock_nested drivers/base/regmap/regmap.c, 468: mutex_lock_nested in regmap_lock_mutex drivers/base/regmap/regmap.c, 2821: [FUNC_PTR]regmap_lock_mutex in regmap_update_bits_base drivers/clk/clk-aspeed.c, 270: regmap_update_bits_base in aspeed_clk_disable drivers/clk/clk-aspeed.c, 267: _raw_spin_lock_irqsave in aspeed_clk_disable [FUNC] mutex_lock_nested drivers/base/regmap/regmap.c, 468: mutex_lock_nested in regmap_lock_mutex drivers/base/regmap/regmap.c, 2503: [FUNC_PTR]regmap_lock_mutex in regmap_read drivers/char/ipmi/bt-bmc.c, 385: regmap_read in bt_bmc_irq [FUNC] mutex_lock_nested drivers/base/regmap/regmap.c, 468: mutex_lock_nested in regmap_lock_mutex drivers/base/regmap/regmap.c, 2821: [FUNC_PTR]regmap_lock_mutex in regmap_update_bits_base drivers/gpu/drm/bridge/synopsys/dw-hdmi.c, 213: regmap_update_bits_base in hdmi_modb drivers/gpu/drm/bridge/synopsys/dw-hdmi.c, 429: hdmi_modb in hdmi_set_cts_n drivers/gpu/drm/bridge/synopsys/dw-hdmi.c, 527: hdmi_set_cts_n in hdmi_set_clk_regenerator drivers/gpu/drm/bridge/synopsys/dw-hdmi.c, 524: spin_lock_irq in hdmi_set_clk_regenerator [FUNC] mutex_lock_nested drivers/base/regmap/regmap.c, 468: mutex_lock_nested in regmap_lock_mutex drivers/base/regmap/regmap.c, 2503: [FUNC_PTR]regmap_lock_mutex in regmap_read drivers/media/platform/atmel/atmel-isc.c, 1603: regmap_read in isc_interrupt (interrupt handler) I find the code about the assignment of regmap_lock_mutex(): if ((bus && bus->fast_io) || config->fast_io) { spin_lock_init(&map->spinlock); map->lock = regmap_lock_spinlock; map->unlock = regmap_unlock_spinlock; lockdep_set_class_and_name(&map->spinlock, lock_key, lock_name); } else { mutex_init(&map->mutex); map->lock = regmap_lock_mutex; map->unlock = regmap_unlock_mutex; lockdep_set_class_and_name(&map->mutex, lock_key, lock_name); } But after reading the code, I cannot find the relationship between the if condition and atomic context. I think assigning regmap_lock_mutex() to map->lock may be not proper. I also find some similar previously reported problems about regmap_lock_mutex(): https://lists.launchpad.net/kernel-packages/msg187700.html https://community.nxp.com/thread/432071 I am not sure whether my analysis and results are right. Could someone please give me explanation? Thanks in advance :) Best wishes, Jia-Ju Bai