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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d62d555374sm19413855ad.16.2026.08.21.06.50.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Aug 2026 06:50:09 -0700 (PDT) Sender: Guenter Roeck Message-ID: Date: Fri, 21 Aug 2026 06:50:07 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hwmon: chipcap2: serialize access to low/high_alarm indicators To: Javier Carrasco Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260821-chipcap2_locks-v1-1-1d8ccabfc1b2@gmail.com> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAmgrMyQFCSbODQkACgkQyx8mb86fmYGcWRAA oRwrk7V8fULqnGGpBIjp7pvR187Yzx+lhMGUHuM5H56TFEqeVwCMLWB2x1YRolYbY4MEFlQg VUFcfeW0OknSr1s6wtrtQm0gdkolM8OcCL9ptTHOg1mmXa4YpW8QJiL0AVtbpE9BroeWGl9v 2TGILPm9mVp+GmMQgkNeCS7Jonq5f5pDUGumAMguWzMFEg+Imt9wr2YA7aGen7KPSqJeQPpj onPKhu7O/KJKkuC50ylxizHzmGx+IUSmOZxN950pZUFvVZH9CwhAAl+NYUtcF5ry/uSYG2U7 DCvpzqOryJRemKN63qt1bjF6cltsXwxjKOw6CvdjJYA3n6xCWLuJ6yk6CAy1Ukh545NhgBAs rGGVkl6TUBi0ixL3EF3RWLa9IMDcHN32r7OBhw6vbul8HqyTFZWY2ksTvlTl+qG3zV6AJuzT WdXmbcKN+TdhO5XlxVlbZoCm7ViBj1+PvIFQZCnLAhqSd/DJlhaq8fFXx1dCUPgQDcD+wo65 qulV/NijfU8bzFfEPgYP/3LP+BSAyFs33y/mdP8kbMxSCjnLEhimQMrSSo/To1Gxp5C97fw5 3m1CaMILGKCmfI1B8iA8zd8ib7t1Rg0qCwcAnvsM36SkrID32GfFbv873bNskJCHAISK3Xkz qo7IYZmjk/IJGbsiGzxUhvicwkgKE9r7a1rOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAmgrMyQFCSbODQkACgkQyx8mb86fmYHlgg/9 H5JeDmB4jsreE9Bn621wZk7NMzxy9STxiVKSh8Mq4pb+IDu1RU2iLyetCY1TiJlcxnE362kj njrfAdqyPteHM+LU59NtEbGwrfcXdQoh4XdMuPA5ADetPLma3YiRa3VsVkLwpnR7ilgwQw6u dycEaOxQ7LUXCs0JaGVVP25Z2hMkHBwx6BlW6EZLNgzGI2rswSZ7SKcsBd1IRHVf0miwIFYy j/UEfAFNW+tbtKPNn3xZTLs3quQN7GdYLh+J0XxITpBZaFOpwEKV+VS36pSLnNl0T5wm0E/y scPJ0OVY7ly5Vm1nnoH4licaU5Y1nSkFR/j2douI5P7Cj687WuNMC6CcFd6j72kRfxklOqXw zvy+2NEcXyziiLXp84130yxAKXfluax9sZhhrhKT6VrD45S6N3HxJpXQ/RY/EX35neH2/F7B RgSloce2+zWfpELyS1qRkCUTt1tlGV2p+y2BPfXzrHn2vxvbhEn1QpQ6t+85FKN8YEhJEygJ F0WaMvQMNrk9UAUziVcUkLU52NS9SXqpVg8vgrO0JKx97IXFPcNh0DWsSj/0Y8HO/RDkGXYn FDMj7fZSPKyPQPmEHg+W/KzxSSfdgWIHF2QaQ0b2q1wOSec4Rti52ohmNSY+KNIW/zODhugJ np3900V20aS7eD9K8GTU0TGC1pyz6IVJwIE= In-Reply-To: <20260821-chipcap2_locks-v1-1-1d8ccabfc1b2@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/21/26 02:22, Javier Carrasco wrote: > Access to low_alarm and high_alarm from the threaded interrupt handlers > and sysfs is not protected by any locking mechanism at the moment, which > can lead to missed events. > > Add a per-interrupt mutex as the two alarm indicators are completely > independent. > > Fixes: 3af350929e75 ("hwmon: Add support for Amphenol ChipCap 2") > Cc: stable@vger.kernel.org > Signed-off-by: Javier Carrasco > --- > This issue was found by Sashiko[1] when an unrelated patch affected > chipcap2.c. The issue is real as the access to the variables is not > protected by any locking mechanism although 2 different sources > (threaded interrupts and sysfs) could modify them. > > The fix has been validated on real hardware with an Amphenol > ChipCap 2 CC2D23S sensor. > Needs explanation: Why can the hwmon subsystem lock not be used ? Guenter > Link: [1] https://lore.kernel.org/linux-hwmon/20260625162114.417EA1F000E9@smtp.kernel.org/ > --- > drivers/hwmon/chipcap2.c | 38 ++++++++++++++++++++++++++++---------- > 1 file changed, 28 insertions(+), 10 deletions(-) > > diff --git a/drivers/hwmon/chipcap2.c b/drivers/hwmon/chipcap2.c > index 086571d556b7..1bb4ec96514e 100644 > --- a/drivers/hwmon/chipcap2.c > +++ b/drivers/hwmon/chipcap2.c > @@ -73,7 +73,11 @@ > > struct cc2_rh_alarm_info { > bool low_alarm; > + /* Serialize accesses to low_alarm from threaded IRQ and sysfs */ > + struct mutex low_alarm_lock; > bool high_alarm; > + /* Serialize accesses to high_alarm from threaded IRQ and sysfs */ > + struct mutex high_alarm_lock; > bool low_alarm_visible; > bool high_alarm_visible; > }; > @@ -500,6 +504,7 @@ static irqreturn_t cc2_low_interrupt(int irq, void *data) > if (cc2->process_irqs) { > hwmon_notify_event(cc2->hwmon, hwmon_humidity, > hwmon_humidity_min_alarm, CC2_CHAN_HUMIDITY); > + guard(mutex)(&cc2->rh_alarm.low_alarm_lock); > cc2->rh_alarm.low_alarm = true; > } > > @@ -513,6 +518,7 @@ static irqreturn_t cc2_high_interrupt(int irq, void *data) > if (cc2->process_irqs) { > hwmon_notify_event(cc2->hwmon, hwmon_humidity, > hwmon_humidity_max_alarm, CC2_CHAN_HUMIDITY); > + guard(mutex)(&cc2->rh_alarm.high_alarm_lock); > cc2->rh_alarm.high_alarm = true; > } > > @@ -529,11 +535,13 @@ static int cc2_humidity_min_alarm_status(struct cc2_data *data, long *val) > if (ret < 0) > return ret; > > - if (data->rh_alarm.low_alarm) { > - *val = (measurement < min_hyst) ? 1 : 0; > - data->rh_alarm.low_alarm = *val; > - } else { > - *val = 0; > + scoped_guard(mutex, &data->rh_alarm.low_alarm_lock) { > + if (data->rh_alarm.low_alarm) { > + *val = (measurement < min_hyst) ? 1 : 0; > + data->rh_alarm.low_alarm = *val; > + } else { > + *val = 0; > + } > } > > return 0; > @@ -549,11 +557,13 @@ static int cc2_humidity_max_alarm_status(struct cc2_data *data, long *val) > if (ret < 0) > return ret; > > - if (data->rh_alarm.high_alarm) { > - *val = (measurement > max_hyst) ? 1 : 0; > - data->rh_alarm.high_alarm = *val; > - } else { > - *val = 0; > + scoped_guard(mutex, &data->rh_alarm.high_alarm_lock) { > + if (data->rh_alarm.high_alarm) { > + *val = (measurement > max_hyst) ? 1 : 0; > + data->rh_alarm.high_alarm = *val; > + } else { > + *val = 0; > + } > } > > return 0; > @@ -720,6 +730,14 @@ static int cc2_probe(struct i2c_client *client) > if (!data) > return -ENOMEM; > > + ret = devm_mutex_init(dev, &data->rh_alarm.low_alarm_lock); > + if (ret) > + return ret; > + > + ret = devm_mutex_init(dev, &data->rh_alarm.high_alarm_lock); > + if (ret) > + return ret; > + > i2c_set_clientdata(client, data); > > data->client = client; > > --- > base-commit: 818bebeb63dd6bf5f4e07e145f6cdbace520a34c > change-id: 20260820-chipcap2_locks-c01013a24a0c > > Best regards,